Re: [PATCH v6 9/9] docs/doxygen: doxygen documentation for grant_table.h

[Luca Fancellu <luca.fancellu@xxxxxxx>]

Hi Stefano,

> On 24 Jun 2021, at 00:34, Stefano Stabellini <sstabellini@xxxxxxxxxx> wrote:
> 
> On Mon, 10 May 2021, Luca Fancellu wrote:
>> Modification to include/public/grant_table.h:
>> 
>> 1) Add doxygen tags to:
>> - Create Grant tables section
>> - include variables in the generated documentation
>> - Used @keepindent/@endkeepindent to enclose comment
>>   section that are indented using spaces, to keep
>>   the indentation.
>> 2) Add .rst file for grant table for Arm64
> 
> Why only arm64?

This is a mistake, it should be just “Add .rst file for grant table"

> 
> 
>> Signed-off-by: Luca Fancellu <luca.fancellu@xxxxxxx>
>> ---
>> v6 changes:
>> - Fix misaligned comment
>> - Moved comments to make them display in the docs
>> - Included more documentation in the docs
>>  (see output here: 
>> https://luca.fancellu.gitlab.io/xen-docs/hypercall-interfaces/common/grant_tables.html)
> 
> It looks much much better. All the info we care about seems to be there.
> The only things that I noticed missing and might be good to keep is the
> small comment about HYPERVISOR_grant_table_op:
> 
> /* ` enum neg_errnoval
> * ` HYPERVISOR_grant_table_op(enum grant_table_op cmd,
> * `                           void *args,
> * `                           unsigned int count)
> * `
> *
> * @args points to an array of a per-command data structure. The array
> * has @count members

Where do you want me to put this comment in the html page? In the end of the 
description in the top of the page?

Cheers,

Luca

> 
> All the changes look good to me.
> 
> 
> 
>> v5 changes:
>> - Move GNTCOPY_* define next to the flags field
>> v4 changes:
>> - Used @keepindent/@endkeepindent doxygen commands
>>  to keep text with spaces indentation.
>> - drop changes to grant_entry_v1 comment, it will
>>  be changed and included in the docs in a future patch
>> - Move docs .rst to "common" folder
>> v3 changes:
>> - removed tags to skip anonymous union/struct
>> - moved back comment pointed out by Jan
>> - moved down defines related to struct gnttab_copy
>>  as pointed out by Jan
>> v2 changes:
>> - Revert back to anonymous union/struct
>> - add doxygen tags to skip anonymous union/struct
>> ---
>> docs/hypercall-interfaces/arm64.rst           |   1 +
>> .../common/grant_tables.rst                   |   9 +
>> docs/xen-doxygen/doxy_input.list              |   1 +
>> xen/include/public/grant_table.h              | 387 +++++++++++-------
>> 4 files changed, 245 insertions(+), 153 deletions(-)
>> create mode 100644 docs/hypercall-interfaces/common/grant_tables.rst
>> 
>> diff --git a/docs/hypercall-interfaces/arm64.rst 
>> b/docs/hypercall-interfaces/arm64.rst
>> index 5e701a2adc..cb4c0d13de 100644
>> --- a/docs/hypercall-interfaces/arm64.rst
>> +++ b/docs/hypercall-interfaces/arm64.rst
>> @@ -8,6 +8,7 @@ Starting points
>> .. toctree::
>>    :maxdepth: 2
>> 
>> +   common/grant_tables
>> 
>> 
>> Functions
>> diff --git a/docs/hypercall-interfaces/common/grant_tables.rst 
>> b/docs/hypercall-interfaces/common/grant_tables.rst
>> new file mode 100644
>> index 0000000000..b8a1ef8759
>> --- /dev/null
>> +++ b/docs/hypercall-interfaces/common/grant_tables.rst
>> @@ -0,0 +1,9 @@
>> +.. SPDX-License-Identifier: CC-BY-4.0
>> +
>> +Grant Tables
>> +============
>> +
>> +.. doxygengroup:: grant_table
>> +   :project: Xen
>> +   :members:
>> +   :undoc-members:
>> diff --git a/docs/xen-doxygen/doxy_input.list 
>> b/docs/xen-doxygen/doxy_input.list
>> index e69de29bb2..233d692fa7 100644
>> --- a/docs/xen-doxygen/doxy_input.list
>> +++ b/docs/xen-doxygen/doxy_input.list
>> @@ -0,0 +1 @@
>> +xen/include/public/grant_table.h
>> diff --git a/xen/include/public/grant_table.h 
>> b/xen/include/public/grant_table.h
>> index 84b1d26b36..dfa5155927 100644
>> --- a/xen/include/public/grant_table.h
>> +++ b/xen/include/public/grant_table.h
>> @@ -25,15 +25,19 @@
>>  * Copyright (c) 2004, K A Fraser
>>  */
>> 
>> +/**
>> + * @file
>> + * @brief Interface for granting foreign access to page frames, and 
>> receiving
>> + * page-ownership transfers.
>> + */
>> +
>> #ifndef __XEN_PUBLIC_GRANT_TABLE_H__
>> #define __XEN_PUBLIC_GRANT_TABLE_H__
>> 
>> #include "xen.h"
>> 
>> -/*
>> - * `incontents 150 gnttab Grant Tables
>> - *
>> - * Xen's grant tables provide a generic mechanism to memory sharing
>> +/**
>> + * @brief Xen's grant tables provide a generic mechanism to memory sharing
>>  * between domains. This shared memory interface underpins the split
>>  * device drivers for block and network IO.
>>  *
>> @@ -51,13 +55,13 @@
>>  * know the real machine address of a page it is sharing. This makes
>>  * it possible to share memory correctly with domains running in
>>  * fully virtualised memory.
>> - */
>> -
>> -/***********************************
>> + *
>>  * GRANT TABLE REPRESENTATION
>> - */
>> -
>> -/* Some rough guidelines on accessing and updating grant-table entries
>> + *
>> + * A grant table comprises a packed array of grant entries in one or more
>> + * page frames shared between Xen and a guest.
>> + *
>> + * Some rough guidelines on accessing and updating grant-table entries
>>  * in a concurrency-safe manner. For more information, Linux contains a
>>  * reference implementation for guest OSes (drivers/xen/grant_table.c, see
>>  * 
>> http://git.kernel.org/?p=linux/kernel/git/torvalds/linux.git;a=blob;f=drivers/xen/grant-table.c;hb=HEAD
>> @@ -66,6 +70,7 @@
>>  *     compiler barrier will still be required.
>>  *
>>  * Introducing a valid entry into the grant table:
>> + * @keepindent
>>  *  1. Write ent->domid.
>>  *  2. Write ent->frame:
>>  *      GTF_permit_access:   Frame to which access is permitted.
>> @@ -73,20 +78,25 @@
>>  *                           frame, or zero if none.
>>  *  3. Write memory barrier (WMB).
>>  *  4. Write ent->flags, inc. valid type.
>> + * @endkeepindent
>>  *
>>  * Invalidating an unused GTF_permit_access entry:
>> + * @keepindent
>>  *  1. flags = ent->flags.
>>  *  2. Observe that !(flags & (GTF_reading|GTF_writing)).
>>  *  3. Check result of SMP-safe CMPXCHG(&ent->flags, flags, 0).
>>  *  NB. No need for WMB as reuse of entry is control-dependent on success of
>>  *      step 3, and all architectures guarantee ordering of ctrl-dep writes.
>> + * @endkeepindent
>>  *
>>  * Invalidating an in-use GTF_permit_access entry:
>> + *
>>  *  This cannot be done directly. Request assistance from the domain 
>> controller
>>  *  which can set a timeout on the use of a grant entry and take necessary
>>  *  action. (NB. This is not yet implemented!).
>>  *
>>  * Invalidating an unused GTF_accept_transfer entry:
>> + * @keepindent
>>  *  1. flags = ent->flags.
>>  *  2. Observe that !(flags & GTF_transfer_committed). [*]
>>  *  3. Check result of SMP-safe CMPXCHG(&ent->flags, flags, 0).
>> @@ -97,29 +107,32 @@
>>  *      transferred frame is written. It is safe for the guest to spin 
>> waiting
>>  *      for this to occur (detect by observing GTF_transfer_completed in
>>  *      ent->flags).
>> + * @endkeepindent
>>  *
>>  * Invalidating a committed GTF_accept_transfer entry:
>>  *  1. Wait for (ent->flags & GTF_transfer_completed).
>>  *
>>  * Changing a GTF_permit_access from writable to read-only:
>> + *
>>  *  Use SMP-safe CMPXCHG to set GTF_readonly, while checking !GTF_writing.
>>  *
>>  * Changing a GTF_permit_access from read-only to writable:
>> + *
>>  *  Use SMP-safe bit-setting instruction.
>> + *
>> + * Data structure fields or defines described below have the following tags:
>> + * * [XEN]: This field is written by Xen and read by the sharing guest.
>> + * * [GST]: This field is written by the guest and read by Xen.
>> + *
>> + * @addtogroup grant_table Grant Tables
>> + * @{
>>  */
>> 
>> -/*
>> +/**
>>  * Reference to a grant entry in a specified domain's grant table.
>>  */
>> typedef uint32_t grant_ref_t;
>> 
>> -/*
>> - * A grant table comprises a packed array of grant entries in one or more
>> - * page frames shared between Xen and a guest.
>> - * [XEN]: This field is written by Xen and read by the sharing guest.
>> - * [GST]: This field is written by the guest and read by Xen.
>> - */
>> -
>> /*
>>  * Version 1 of the grant table entry structure is maintained purely
>>  * for backwards compatibility.  New guests should use version 2.
>> @@ -129,15 +142,17 @@ typedef uint32_t grant_ref_t;
>> #define grant_entry_v1_t grant_entry_t
>> #endif
>> struct grant_entry_v1 {
>> -    /* GTF_xxx: various type and flag information.  [XEN,GST] */
>> +    /** GTF_xxx: various type and flag information.  [XEN,GST] */
>>     uint16_t flags;
>> -    /* The domain being granted foreign privileges. [GST] */
>> +    /** The domain being granted foreign privileges. [GST] */
>>     domid_t  domid;
>> -    /*
>> +    /**
>> +     * @keepindent
>>      * GTF_permit_access: GFN that @domid is allowed to map and access. [GST]
>>      * GTF_accept_transfer: GFN that @domid is allowed to transfer into. 
>> [GST]
>>      * GTF_transfer_completed: MFN whose ownership transferred by @domid
>>      *                         (non-translated guests only). [XEN]
>> +     * @endkeepindent
>>      */
>>     uint32_t frame;
>> };
>> @@ -150,60 +165,99 @@ typedef struct grant_entry_v1 grant_entry_v1_t;
>> #define GNTTAB_RESERVED_CONSOLE        0
>> #define GNTTAB_RESERVED_XENSTORE       1
>> 
>> -/*
>> - * Type of grant entry.
>> - *  GTF_invalid: This grant entry grants no privileges.
>> - *  GTF_permit_access: Allow @domid to map/access @frame.
>> - *  GTF_accept_transfer: Allow @domid to transfer ownership of one page 
>> frame
>> - *                       to this guest. Xen writes the page number to 
>> @frame.
>> - *  GTF_transitive: Allow @domid to transitively access a subrange of
>> - *                  @trans_grant in @trans_domid.  No mappings are allowed.
>> - */
>> +/** This type of grant entry grants no privileges. */
>> #define GTF_invalid         (0U<<0)
>> +
>> +/** This type of grant entry allow \@domid to map/access \@frame. */
>> #define GTF_permit_access   (1U<<0)
>> +
>> +/**
>> + * This type of grant entry allow \@domid to transfer ownership of one 
>> pageframe
>> + * to this guest. Xen writes the page number to \@frame.
>> + */
>> #define GTF_accept_transfer (2U<<0)
>> +
>> +/**
>> + * This type of grant entry allow \@domid to transitively access a subrange 
>> of
>> + * \@trans_grant in \@trans_domid.  No mappings are allowed.
>> + */
>> #define GTF_transitive      (3U<<0)
>> +
>> #define GTF_type_mask       (3U<<0)
>> 
>> -/*
>> - * Subflags for GTF_permit_access and GTF_transitive.
>> - *  GTF_readonly: Restrict @domid to read-only mappings and accesses. [GST]
>> - *  GTF_reading: Grant entry is currently mapped for reading by @domid. 
>> [XEN]
>> - *  GTF_writing: Grant entry is currently mapped for writing by @domid. 
>> [XEN]
>> - * Further subflags for GTF_permit_access only.
>> - *  GTF_PAT, GTF_PWT, GTF_PCD: (x86) cache attribute flags to be used for
>> - *                             mappings of the grant [GST]
>> - *  GTF_sub_page: Grant access to only a subrange of the page.  @domid
>> - *                will only be allowed to copy from the grant, and not
>> - *                map it. [GST]
>> +/**
>> + * @def GTF_readonly
>> + * Subflag for GTF_permit_access and GTF_transitive: Restrict \@domid to
>> + * read-only mappings and accesses. [GST]
>>  */
>> #define _GTF_readonly       (2)
>> #define GTF_readonly        (1U<<_GTF_readonly)
>> +
>> +/**
>> + * @def GTF_reading
>> + * Subflag for GTF_permit_access and GTF_transitive: Grant entry is 
>> currently
>> + * mapped for reading by \@domid. [XEN]
>> + */
>> #define _GTF_reading        (3)
>> #define GTF_reading         (1U<<_GTF_reading)
>> +
>> +/**
>> + * @def GTF_writing
>> + * Subflag for GTF_permit_access and GTF_transitive: Grant entry is 
>> currently
>> + * mapped for writing by \@domid. [XEN]
>> + */
>> #define _GTF_writing        (4)
>> #define GTF_writing         (1U<<_GTF_writing)
>> +
>> +/**
>> + * @def GTF_PWT
>> + * Subflag for GTF_permit_access only: (x86) cache attribute flags to be 
>> used
>> + * for mappings of the grant [GST]
>> + */
>> #define _GTF_PWT            (5)
>> #define GTF_PWT             (1U<<_GTF_PWT)
>> +
>> +/**
>> + * @def GTF_PCD
>> + * Subflag for GTF_permit_access only: (x86) cache attribute flags to be 
>> used
>> + * for mappings of the grant [GST]
>> + */
>> #define _GTF_PCD            (6)
>> #define GTF_PCD             (1U<<_GTF_PCD)
>> +
>> +/**
>> + * @def GTF_PAT
>> + * Subflag for GTF_permit_access only: (x86) cache attribute flags to be 
>> used
>> + * for mappings of the grant [GST]
>> + */
>> #define _GTF_PAT            (7)
>> #define GTF_PAT             (1U<<_GTF_PAT)
>> +
>> +/**
>> + * @def GTF_sub_page
>> + * Subflag for GTF_permit_access only: Grant access to only a subrange of 
>> the
>> + * page. \@domid will only be allowed to copy from the grant, and not map 
>> it.
>> + * [GST]
>> + */
>> #define _GTF_sub_page       (8)
>> #define GTF_sub_page        (1U<<_GTF_sub_page)
>> 
>> -/*
>> - * Subflags for GTF_accept_transfer:
>> - *  GTF_transfer_committed: Xen sets this flag to indicate that it is 
>> committed
>> - *      to transferring ownership of a page frame. When a guest sees this 
>> flag
>> - *      it must /not/ modify the grant entry until GTF_transfer_completed is
>> - *      set by Xen.
>> - *  GTF_transfer_completed: It is safe for the guest to spin-wait on this 
>> flag
>> - *      after reading GTF_transfer_committed. Xen will always write the 
>> frame
>> - *      address, followed by ORing this flag, in a timely manner.
>> +/**
>> + * @def GTF_transfer_committed
>> + * Subflag for GTF_accept_transfer: Xen sets this flag to indicate that it 
>> is
>> + * committed to transferring ownership of a page frame. When a guest sees 
>> this
>> + * flag it must /not/ modify the grant entry until GTF_transfer_completed is
>> + * set by Xen.
>>  */
>> #define _GTF_transfer_committed (2)
>> #define GTF_transfer_committed  (1U<<_GTF_transfer_committed)
>> +
>> +/**
>> + * @def GTF_transfer_completed
>> + * Subflag for GTF_accept_transfer: It is safe for the guest to spin-wait on
>> + * this flag after reading GTF_transfer_committed. Xen will always write the
>> + * frame address, followed by ORing this flag, in a timely manner.
>> + */
>> #define _GTF_transfer_completed (3)
>> #define GTF_transfer_completed  (1U<<_GTF_transfer_completed)
>> 
>> @@ -228,17 +282,17 @@ struct grant_entry_header {
>> };
>> typedef struct grant_entry_header grant_entry_header_t;
>> 
>> -/*
>> +/**
>>  * Version 2 of the grant entry structure.
>>  */
>> union grant_entry_v2 {
>>     grant_entry_header_t hdr;
>> 
>> -    /*
>> +    /**
>>      * This member is used for V1-style full page grants, where either:
>>      *
>> -     * -- hdr.type is GTF_accept_transfer, or
>> -     * -- hdr.type is GTF_permit_access and GTF_sub_page is not set.
>> +     * * hdr.type is GTF_accept_transfer, or
>> +     * * hdr.type is GTF_permit_access and GTF_sub_page is not set.
>>      *
>>      * In that case, the frame field has the same semantics as the
>>      * field of the same name in the V1 entry structure.
>> @@ -249,10 +303,10 @@ union grant_entry_v2 {
>>         uint64_t frame;
>>     } full_page;
>> 
>> -    /*
>> +    /**
>>      * If the grant type is GTF_grant_access and GTF_sub_page is set,
>> -     * @domid is allowed to access bytes [@page_off,@page_off+@length)
>> -     * in frame @frame.
>> +     * \@domid is allowed to access bytes [\@page_off,\@page_off+\@length)
>> +     * in frame \@frame.
>>      */
>>     struct {
>>         grant_entry_header_t hdr;
>> @@ -261,9 +315,9 @@ union grant_entry_v2 {
>>         uint64_t frame;
>>     } sub_page;
>> 
>> -    /*
>> -     * If the grant is GTF_transitive, @domid is allowed to use the
>> -     * grant @gref in domain @trans_domid, as if it was the local
>> +    /**
>> +     * If the grant is GTF_transitive, \@domid is allowed to use the
>> +     * grant \@gref in domain \@trans_domid, as if it was the local
>>      * domain.  Obviously, the transitive access must be compatible
>>      * with the original grant.
>>      *
>> @@ -277,7 +331,7 @@ union grant_entry_v2 {
>>         grant_ref_t gref;
>>     } transitive;
>> 
>> -    uint32_t __spacer[4]; /* Pad to a power of two */
>> +    uint32_t __spacer[4]; /**< Pad to a power of two */
>> };
>> typedef union grant_entry_v2 grant_entry_v2_t;
>> 
>> @@ -317,24 +371,25 @@ typedef uint16_t grant_status_t;
>> #endif /* __XEN_INTERFACE_VERSION__ */
>> /* ` } */
>> 
>> -/*
>> +/**
>>  * Handle to track a mapping created via a grant reference.
>>  */
>> typedef uint32_t grant_handle_t;
>> 
>> -/*
>> - * GNTTABOP_map_grant_ref: Map the grant entry (<dom>,<ref>) for access
>> - * by devices and/or host CPUs. If successful, <handle> is a tracking number
>> - * that must be presented later to destroy the mapping(s). On error, 
>> <status>
>> +/**
>> + * GNTTABOP_map_grant_ref: Map the grant entry (\@dom,\@ref) for access
>> + * by devices and/or host CPUs. If successful, \@handle is a tracking number
>> + * that must be presented later to destroy the mapping(s). On error, 
>> \@status
>>  * is a negative status code.
>> + *
>>  * NOTES:
>> - *  1. If GNTMAP_device_map is specified then <dev_bus_addr> is the address
>> + *  1. If GNTMAP_device_map is specified then \@dev_bus_addr is the address
>>  *     via which I/O devices may access the granted frame.
>>  *  2. If GNTMAP_host_map is specified then a mapping will be added at
>>  *     either a host virtual address in the current address space, or at
>>  *     a PTE at the specified machine address.  The type of mapping to
>>  *     perform is selected through the GNTMAP_contains_pte flag, and the
>> - *     address is specified in <host_addr>.
>> + *     address is specified in \@host_addr.
>>  *  3. Mappings should only be destroyed via GNTTABOP_unmap_grant_ref. If a
>>  *     host mapping is destroyed by other means then it is *NOT* guaranteed
>>  *     to be accounted to the correct grant reference!
>> @@ -342,25 +397,26 @@ typedef uint32_t grant_handle_t;
>> struct gnttab_map_grant_ref {
>>     /* IN parameters. */
>>     uint64_t host_addr;
>> -    uint32_t flags;               /* GNTMAP_* */
>> +    uint32_t flags;               /**< GNTMAP_* */
>>     grant_ref_t ref;
>>     domid_t  dom;
>>     /* OUT parameters. */
>> -    int16_t  status;              /* => enum grant_status */
>> +    int16_t  status;              /**< GNTST_* status code */
>>     grant_handle_t handle;
>>     uint64_t dev_bus_addr;
>> };
>> typedef struct gnttab_map_grant_ref gnttab_map_grant_ref_t;
>> DEFINE_XEN_GUEST_HANDLE(gnttab_map_grant_ref_t);
>> 
>> -/*
>> +/**
>>  * GNTTABOP_unmap_grant_ref: Destroy one or more grant-reference mappings
>> - * tracked by <handle>. If <host_addr> or <dev_bus_addr> is zero, that
>> + * tracked by \@handle. If \@host_addr or \@dev_bus_addr is zero, that
>>  * field is ignored. If non-zero, they must refer to a device/host mapping
>> - * that is tracked by <handle>
>> + * that is tracked by \@handle
>> + *
>>  * NOTES:
>>  *  1. The call may fail in an undefined manner if either mapping is not
>> - *     tracked by <handle>.
>> + *     tracked by \@handle.
>>  *  3. After executing a batch of unmaps, it is guaranteed that no stale
>>  *     mappings will remain in the device or host TLBs.
>>  */
>> @@ -370,18 +426,19 @@ struct gnttab_unmap_grant_ref {
>>     uint64_t dev_bus_addr;
>>     grant_handle_t handle;
>>     /* OUT parameters. */
>> -    int16_t  status;              /* => enum grant_status */
>> +    int16_t  status;              /**< GNTST_* status code */
>> };
>> typedef struct gnttab_unmap_grant_ref gnttab_unmap_grant_ref_t;
>> DEFINE_XEN_GUEST_HANDLE(gnttab_unmap_grant_ref_t);
>> 
>> -/*
>> - * GNTTABOP_setup_table: Set up a grant table for <dom> comprising at least
>> - * <nr_frames> pages. The frame addresses are written to the <frame_list>.
>> - * Only <nr_frames> addresses are written, even if the table is larger.
>> +/**
>> + * GNTTABOP_setup_table: Set up a grant table for \@dom comprising at least
>> + * \@nr_frames pages. The frame addresses are written to the \@frame_list.
>> + * Only \@nr_frames addresses are written, even if the table is larger.
>> + *
>>  * NOTES:
>> - *  1. <dom> may be specified as DOMID_SELF.
>> - *  2. Only a sufficiently-privileged domain may specify <dom> != 
>> DOMID_SELF.
>> + *  1. \@dom may be specified as DOMID_SELF.
>> + *  2. Only a sufficiently-privileged domain may specify \@dom != 
>> DOMID_SELF.
>>  *  3. Xen may not support more than a single grant-table page per domain.
>>  */
>> struct gnttab_setup_table {
>> @@ -389,7 +446,7 @@ struct gnttab_setup_table {
>>     domid_t  dom;
>>     uint32_t nr_frames;
>>     /* OUT parameters. */
>> -    int16_t  status;              /* => enum grant_status */
>> +    int16_t  status;              /**< GNTST_* status code */
>> #if __XEN_INTERFACE_VERSION__ < 0x00040300
>>     XEN_GUEST_HANDLE(ulong) frame_list;
>> #else
>> @@ -399,7 +456,7 @@ struct gnttab_setup_table {
>> typedef struct gnttab_setup_table gnttab_setup_table_t;
>> DEFINE_XEN_GUEST_HANDLE(gnttab_setup_table_t);
>> 
>> -/*
>> +/**
>>  * GNTTABOP_dump_table: Dump the contents of the grant table to the
>>  * xen console. Debugging use only.
>>  */
>> @@ -407,14 +464,14 @@ struct gnttab_dump_table {
>>     /* IN parameters. */
>>     domid_t dom;
>>     /* OUT parameters. */
>> -    int16_t status;               /* => enum grant_status */
>> +    int16_t status;               /**< GNTST_* status code */
>> };
>> typedef struct gnttab_dump_table gnttab_dump_table_t;
>> DEFINE_XEN_GUEST_HANDLE(gnttab_dump_table_t);
>> 
>> -/*
>> - * GNTTABOP_transfer: Transfer <frame> to a foreign domain. The foreign 
>> domain
>> - * has previously registered its interest in the transfer via <domid, ref>.
>> +/**
>> + * GNTTABOP_transfer: Transfer \@frame to a foreign domain. The foreign 
>> domain
>> + * has previously registered its interest in the transfer via \@domid, 
>> \@ref.
>>  *
>>  * Note that, even if the transfer fails, the specified page no longer 
>> belongs
>>  * to the calling domain *unless* the error is GNTST_bad_page.
>> @@ -427,13 +484,13 @@ struct gnttab_transfer {
>>     domid_t       domid;
>>     grant_ref_t   ref;
>>     /* OUT parameters. */
>> -    int16_t       status;
>> +    int16_t       status;               /**< GNTST_* status code */
>> };
>> typedef struct gnttab_transfer gnttab_transfer_t;
>> DEFINE_XEN_GUEST_HANDLE(gnttab_transfer_t);
>> 
>> 
>> -/*
>> +/**
>>  * GNTTABOP_copy: Hypervisor based copy
>>  * source and destinations can be eithers MFNs or, for foreign domains,
>>  * grant references. the foreign domain has to grant read/write access
>> @@ -451,11 +508,6 @@ DEFINE_XEN_GUEST_HANDLE(gnttab_transfer_t);
>>  * bytes to be copied.
>>  */
>> 
>> -#define _GNTCOPY_source_gref      (0)
>> -#define GNTCOPY_source_gref       (1<<_GNTCOPY_source_gref)
>> -#define _GNTCOPY_dest_gref        (1)
>> -#define GNTCOPY_dest_gref         (1<<_GNTCOPY_dest_gref)
>> -
>> struct gnttab_copy {
>>     /* IN parameters. */
>>     struct gnttab_copy_ptr {
>> @@ -467,19 +519,24 @@ struct gnttab_copy {
>>         uint16_t offset;
>>     } source, dest;
>>     uint16_t      len;
>> -    uint16_t      flags;          /* GNTCOPY_* */
>> +    uint16_t      flags;          /**< GNTCOPY_* */
>> +#define _GNTCOPY_source_gref      (0)
>> +#define GNTCOPY_source_gref       (1<<_GNTCOPY_source_gref)
>> +#define _GNTCOPY_dest_gref        (1)
>> +#define GNTCOPY_dest_gref         (1<<_GNTCOPY_dest_gref)
>>     /* OUT parameters. */
>>     int16_t       status;
>> };
>> typedef struct gnttab_copy  gnttab_copy_t;
>> DEFINE_XEN_GUEST_HANDLE(gnttab_copy_t);
>> 
>> -/*
>> +/**
>>  * GNTTABOP_query_size: Query the current and maximum sizes of the shared
>>  * grant table.
>> + *
>>  * NOTES:
>> - *  1. <dom> may be specified as DOMID_SELF.
>> - *  2. Only a sufficiently-privileged domain may specify <dom> != 
>> DOMID_SELF.
>> + *  1. \@dom may be specified as DOMID_SELF.
>> + *  2. Only a sufficiently-privileged domain may specify \@dom != 
>> DOMID_SELF.
>>  */
>> struct gnttab_query_size {
>>     /* IN parameters. */
>> @@ -487,19 +544,20 @@ struct gnttab_query_size {
>>     /* OUT parameters. */
>>     uint32_t nr_frames;
>>     uint32_t max_nr_frames;
>> -    int16_t  status;              /* => enum grant_status */
>> +    int16_t  status;              /**< GNTST_* status code */
>> };
>> typedef struct gnttab_query_size gnttab_query_size_t;
>> DEFINE_XEN_GUEST_HANDLE(gnttab_query_size_t);
>> 
>> -/*
>> +/**
>>  * GNTTABOP_unmap_and_replace: Destroy one or more grant-reference mappings
>> - * tracked by <handle> but atomically replace the page table entry with one
>> - * pointing to the machine address under <new_addr>.  <new_addr> will be
>> + * tracked by \@handle but atomically replace the page table entry with one
>> + * pointing to the machine address under \@new_addr. \@new_addr will be
>>  * redirected to the null entry.
>> + *
>>  * NOTES:
>>  *  1. The call may fail in an undefined manner if either mapping is not
>> - *     tracked by <handle>.
>> + *     tracked by \@handle.
>>  *  2. After executing a batch of unmaps, it is guaranteed that no stale
>>  *     mappings will remain in the device or host TLBs.
>>  */
>> @@ -509,13 +567,13 @@ struct gnttab_unmap_and_replace {
>>     uint64_t new_addr;
>>     grant_handle_t handle;
>>     /* OUT parameters. */
>> -    int16_t  status;              /* => enum grant_status */
>> +    int16_t  status;              /**< GNTST_* status code */
>> };
>> typedef struct gnttab_unmap_and_replace gnttab_unmap_and_replace_t;
>> DEFINE_XEN_GUEST_HANDLE(gnttab_unmap_and_replace_t);
>> 
>> #if __XEN_INTERFACE_VERSION__ >= 0x0003020a
>> -/*
>> +/**
>>  * GNTTABOP_set_version: Request a particular version of the grant
>>  * table shared table structure.  This operation may be used to toggle
>>  * between different versions, but must be performed while no grants
>> @@ -529,32 +587,33 @@ typedef struct gnttab_set_version gnttab_set_version_t;
>> DEFINE_XEN_GUEST_HANDLE(gnttab_set_version_t);
>> 
>> 
>> -/*
>> +/**
>>  * GNTTABOP_get_status_frames: Get the list of frames used to store grant
>> - * status for <dom>. In grant format version 2, the status is separated
>> + * status for \@dom. In grant format version 2, the status is separated
>>  * from the other shared grant fields to allow more efficient synchronization
>>  * using barriers instead of atomic cmpexch operations.
>> - * <nr_frames> specify the size of vector <frame_list>.
>> - * The frame addresses are returned in the <frame_list>.
>> - * Only <nr_frames> addresses are returned, even if the table is larger.
>> + * \@nr_frames specify the size of vector \@frame_list.
>> + * The frame addresses are returned in the \@frame_list.
>> + * Only \@nr_frames addresses are returned, even if the table is larger.
>> + *
>>  * NOTES:
>> - *  1. <dom> may be specified as DOMID_SELF.
>> - *  2. Only a sufficiently-privileged domain may specify <dom> != 
>> DOMID_SELF.
>> + *  1. \@dom may be specified as DOMID_SELF.
>> + *  2. Only a sufficiently-privileged domain may specify \@dom != 
>> DOMID_SELF.
>>  */
>> struct gnttab_get_status_frames {
>>     /* IN parameters. */
>>     uint32_t nr_frames;
>>     domid_t  dom;
>>     /* OUT parameters. */
>> -    int16_t  status;              /* => enum grant_status */
>> +    int16_t  status;              /**< GNTST_* status code */
>>     XEN_GUEST_HANDLE(uint64_t) frame_list;
>> };
>> typedef struct gnttab_get_status_frames gnttab_get_status_frames_t;
>> DEFINE_XEN_GUEST_HANDLE(gnttab_get_status_frames_t);
>> 
>> -/*
>> +/**
>>  * GNTTABOP_get_version: Get the grant table version which is in
>> - * effect for domain <dom>.
>> + * effect for domain \@dom.
>>  */
>> struct gnttab_get_version {
>>     /* IN parameters */
>> @@ -566,7 +625,7 @@ struct gnttab_get_version {
>> typedef struct gnttab_get_version gnttab_get_version_t;
>> DEFINE_XEN_GUEST_HANDLE(gnttab_get_version_t);
>> 
>> -/*
>> +/**
>>  * GNTTABOP_swap_grant_ref: Swap the contents of two grant entries.
>>  */
>> struct gnttab_swap_grant_ref {
>> @@ -574,12 +633,12 @@ struct gnttab_swap_grant_ref {
>>     grant_ref_t ref_a;
>>     grant_ref_t ref_b;
>>     /* OUT parameters */
>> -    int16_t status;             /* => enum grant_status */
>> +    int16_t status;             /**< GNTST_* status code */
>> };
>> typedef struct gnttab_swap_grant_ref gnttab_swap_grant_ref_t;
>> DEFINE_XEN_GUEST_HANDLE(gnttab_swap_grant_ref_t);
>> 
>> -/*
>> +/**
>>  * Issue one or more cache maintenance operations on a portion of a
>>  * page granted to the calling domain by a foreign domain.
>>  */
>> @@ -588,8 +647,8 @@ struct gnttab_cache_flush {
>>         uint64_t dev_bus_addr;
>>         grant_ref_t ref;
>>     } a;
>> -    uint16_t offset; /* offset from start of grant */
>> -    uint16_t length; /* size within the grant */
>> +    uint16_t offset; /**< offset from start of grant */
>> +    uint16_t length; /**< size within the grant */
>> #define GNTTAB_CACHE_CLEAN          (1u<<0)
>> #define GNTTAB_CACHE_INVAL          (1u<<1)
>> #define GNTTAB_CACHE_SOURCE_GREF    (1u<<31)
>> @@ -600,40 +659,60 @@ DEFINE_XEN_GUEST_HANDLE(gnttab_cache_flush_t);
>> 
>> #endif /* __XEN_INTERFACE_VERSION__ */
>> 
>> -/*
>> - * Bitfield values for gnttab_map_grant_ref.flags.
>> +/**
>> + * @def GNTMAP_device_map
>> + * Bitfield value for gnttab_map_grant_ref.flags: Map the grant entry for
>> + * access by I/O devices.
>>  */
>> - /* Map the grant entry for access by I/O devices. */
>> #define _GNTMAP_device_map      (0)
>> #define GNTMAP_device_map       (1<<_GNTMAP_device_map)
>> - /* Map the grant entry for access by host CPUs. */
>> +
>> +/**
>> + * @def GNTMAP_host_map
>> + * Bitfield value for gnttab_map_grant_ref.flags: Map the grant entry for
>> + * access by host CPUs.
>> + */
>> #define _GNTMAP_host_map        (1)
>> #define GNTMAP_host_map         (1<<_GNTMAP_host_map)
>> - /* Accesses to the granted frame will be restricted to read-only access. */
>> +
>> +/**
>> + * @def GNTMAP_readonly
>> + * Bitfield value for gnttab_map_grant_ref.flags: Accesses to the granted 
>> frame
>> + * will be restricted to read-only access.
>> + */
>> #define _GNTMAP_readonly        (2)
>> #define GNTMAP_readonly         (1<<_GNTMAP_readonly)
>> - /*
>> -  * GNTMAP_host_map subflag:
>> -  *  0 => The host mapping is usable only by the guest OS.
>> -  *  1 => The host mapping is usable by guest OS + current application.
>> -  */
>> +
>> +/**
>> + * @def GNTMAP_application_map
>> + * Bitfield value for gnttab_map_grant_ref.flags.
>> + *
>> + * GNTMAP_host_map subflag:
>> + * * 0 => The host mapping is usable only by the guest OS.
>> + * * 1 => The host mapping is usable by guest OS + current application.
>> + */
>> #define _GNTMAP_application_map (3)
>> #define GNTMAP_application_map  (1<<_GNTMAP_application_map)
>> 
>> - /*
>> -  * GNTMAP_contains_pte subflag:
>> -  *  0 => This map request contains a host virtual address.
>> -  *  1 => This map request contains the machine addess of the PTE to update.
>> -  */
>> +/**
>> + * @def GNTMAP_contains_pte
>> + * Bitfield value for gnttab_map_grant_ref.flags.
>> + *
>> + * GNTMAP_contains_pte subflag:
>> + * * 0 => This map request contains a host virtual address.
>> + * * 1 => This map request contains the machine addess of the PTE to update.
>> + */
>> #define _GNTMAP_contains_pte    (4)
>> #define GNTMAP_contains_pte     (1<<_GNTMAP_contains_pte)
>> 
>> #define _GNTMAP_can_fail        (5)
>> #define GNTMAP_can_fail         (1<<_GNTMAP_can_fail)
>> 
>> -/*
>> - * Bits to be placed in guest kernel available PTE bits (architecture
>> - * dependent; only supported when XENFEAT_gnttab_map_avail_bits is set).
>> +/**
>> + * @def GNTMAP_guest_avail_mask
>> + * Bitfield value for gnttab_map_grant_ref.flags: Bits to be placed in guest
>> + * kernel available PTE bits (architecture dependent; only supported when
>> + * XENFEAT_gnttab_map_avail_bits is set).
>>  */
>> #define _GNTMAP_guest_avail0    (16)
>> #define GNTMAP_guest_avail_mask ((uint32_t)~0 << _GNTMAP_guest_avail0)
>> @@ -641,21 +720,19 @@ DEFINE_XEN_GUEST_HANDLE(gnttab_cache_flush_t);
>> /*
>>  * Values for error status returns. All errors are -ve.
>>  */
>> -/* ` enum grant_status { */
>> -#define GNTST_okay             (0)  /* Normal return.                       
>>  */
>> -#define GNTST_general_error    (-1) /* General undefined error.             
>>  */
>> -#define GNTST_bad_domain       (-2) /* Unrecognsed domain id.               
>>  */
>> -#define GNTST_bad_gntref       (-3) /* Unrecognised or inappropriate 
>> gntref. */
>> -#define GNTST_bad_handle       (-4) /* Unrecognised or inappropriate 
>> handle. */
>> -#define GNTST_bad_virt_addr    (-5) /* Inappropriate virtual address to 
>> map. */
>> -#define GNTST_bad_dev_addr     (-6) /* Inappropriate device address to 
>> unmap.*/
>> -#define GNTST_no_device_space  (-7) /* Out of space in I/O MMU.             
>>  */
>> -#define GNTST_permission_denied (-8) /* Not enough privilege for operation. 
>>  */
>> -#define GNTST_bad_page         (-9) /* Specified page was invalid for op.   
>>  */
>> -#define GNTST_bad_copy_arg    (-10) /* copy arguments cross page boundary.  
>>  */
>> -#define GNTST_address_too_big (-11) /* transfer page address too large.     
>>  */
>> -#define GNTST_eagain          (-12) /* Operation not done; try again.       
>>  */
>> -/* ` } */
>> +#define GNTST_okay             (0)  /**< Normal return.                     
>>    */
>> +#define GNTST_general_error    (-1) /**< General undefined error.           
>>    */
>> +#define GNTST_bad_domain       (-2) /**< Unrecognsed domain id.             
>>    */
>> +#define GNTST_bad_gntref       (-3) /**< Unrecognised or inappropriate 
>> gntref. */
>> +#define GNTST_bad_handle       (-4) /**< Unrecognised or inappropriate 
>> handle. */
>> +#define GNTST_bad_virt_addr    (-5) /**< Inappropriate virtual address to 
>> map. */
>> +#define GNTST_bad_dev_addr     (-6) /**< Inappropriate device address to 
>> unmap.*/
>> +#define GNTST_no_device_space  (-7) /**< Out of space in I/O MMU.           
>>    */
>> +#define GNTST_permission_denied (-8) /**< Not enough privilege for 
>> operation.  */
>> +#define GNTST_bad_page         (-9) /**< Specified page was invalid for op. 
>>    */
>> +#define GNTST_bad_copy_arg    (-10) /**< copy arguments cross page 
>> boundary.   */
>> +#define GNTST_address_too_big (-11) /**< transfer page address too large.   
>>    */
>> +#define GNTST_eagain          (-12) /**< Operation not done; try again.     
>>    */
>> 
>> #define GNTTABOP_error_msgs {                   \
>>     "okay",                                     \
>> @@ -673,6 +750,10 @@ DEFINE_XEN_GUEST_HANDLE(gnttab_cache_flush_t);
>>     "operation not done; try again"             \
>> }
>> 
>> +/**
>> + * @}
>> + */
>> +
>> #endif /* __XEN_PUBLIC_GRANT_TABLE_H__ */
>> 
>> /*
>> -- 
>> 2.17.1
>>