Re: [Xen-devel] [PATCH v3 1/2] Differentiate IO/mem resources tracked by ioreq server

[Paul Durrant <Paul.Durrant@xxxxxxxxxx>]

> -----Original Message-----
> From: Andrew Cooper [mailto:andrew.cooper3@xxxxxxxxxx]
> Sent: 10 August 2015 11:56
> To: Paul Durrant; Wei Liu; Yu Zhang
> Cc: xen-devel@xxxxxxxxxxxxx; Ian Jackson; Stefano Stabellini; Ian Campbell;
> Keir (Xen.org); jbeulich@xxxxxxxx; Kevin Tian; zhiyuan.lv@xxxxxxxxx
> Subject: Re: [PATCH v3 1/2] Differentiate IO/mem resources tracked by ioreq
> server
> 
> On 10/08/15 09:33, Paul Durrant wrote:
> >> -----Original Message-----
> >> From: Wei Liu [mailto:wei.liu2@xxxxxxxxxx]
> >> Sent: 10 August 2015 09:26
> >> To: Yu Zhang
> >> Cc: xen-devel@xxxxxxxxxxxxx; Paul Durrant; Ian Jackson; Stefano Stabellini;
> Ian
> >> Campbell; Wei Liu; Keir (Xen.org); jbeulich@xxxxxxxx; Andrew Cooper;
> >> Kevin Tian; zhiyuan.lv@xxxxxxxxx
> >> Subject: Re: [PATCH v3 1/2] Differentiate IO/mem resources tracked by
> ioreq
> >> server
> >>
> >> On Mon, Aug 10, 2015 at 11:33:40AM +0800, Yu Zhang wrote:
> >>> Currently in ioreq server, guest write-protected ram pages are
> >>> tracked in the same rangeset with device mmio resources. Yet
> >>> unlike device mmio, which can be in big chunks, the guest write-
> >>> protected pages may be discrete ranges with 4K bytes each.
> >>>
> >>> This patch uses a seperate rangeset for the guest ram pages.
> >>> And a new ioreq type, IOREQ_TYPE_MEM, is defined.
> >>>
> >>> Note: Previously, a new hypercall or subop was suggested to map
> >>> write-protected pages into ioreq server. However, it turned out
> >>> handler of this new hypercall would be almost the same with the
> >>> existing pair - HVMOP_[un]map_io_range_to_ioreq_server, and there's
> >>> already a type parameter in this hypercall. So no new hypercall
> >>> defined, only a new type is introduced.
> >>>
> >>> Signed-off-by: Yu Zhang <yu.c.zhang@xxxxxxxxxxxxxxx>
> >>> ---
> >>>  tools/libxc/include/xenctrl.h    | 39 +++++++++++++++++++++++---
> >>>  tools/libxc/xc_domain.c          | 59
> >> ++++++++++++++++++++++++++++++++++++++--
> >>
> >> FWIW the hypercall wrappers look correct to me.
> >>
> >>> diff --git a/xen/include/public/hvm/hvm_op.h
> >> b/xen/include/public/hvm/hvm_op.h
> >>> index 014546a..9106cb9 100644
> >>> --- a/xen/include/public/hvm/hvm_op.h
> >>> +++ b/xen/include/public/hvm/hvm_op.h
> >>> @@ -329,8 +329,9 @@ struct xen_hvm_io_range {
> >>>      ioservid_t id;               /* IN - server id */
> >>>      uint32_t type;               /* IN - type of range */
> >>>  # define HVMOP_IO_RANGE_PORT   0 /* I/O port range */
> >>> -# define HVMOP_IO_RANGE_MEMORY 1 /* MMIO range */
> >>> +# define HVMOP_IO_RANGE_MMIO   1 /* MMIO range */
> >>>  # define HVMOP_IO_RANGE_PCI    2 /* PCI segment/bus/dev/func
> range
> >> */
> >>> +# define HVMOP_IO_RANGE_MEMORY 3 /* MEMORY range */
> >> This looks problematic. Maybe you can get away with this because this is
> >> a toolstack-only interface?
> >>
> > Indeed, the old name is a bit problematic. Presumably re-use like this
> would require an interface version change and some if-defery.
> 
> I assume it is an interface used by qemu, so this patch in its currently
> state will break things.

If QEMU were re-built against the updated header, yes.

  Paul

> 
> ~Andrew

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