Re: [Xen-devel] [PATCH] xen/privcmd: add IOCTL_PRIVCMD_MMAP_RESOURCE

[Paul Durrant <Paul.Durrant@xxxxxxxxxx>]

> -----Original Message-----
> From: Paul Durrant [mailto:paul.durrant@xxxxxxxxxx]
> Sent: 05 April 2018 10:32
> To: xen-devel@xxxxxxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx;
> x86@xxxxxxxxxx
> Cc: Paul Durrant <Paul.Durrant@xxxxxxxxxx>; Boris Ostrovsky
> <boris.ostrovsky@xxxxxxxxxx>; Juergen Gross <jgross@xxxxxxxx>; Thomas
> Gleixner <tglx@xxxxxxxxxxxxx>; Ingo Molnar <mingo@xxxxxxxxxx>
> Subject: [PATCH] xen/privcmd: add IOCTL_PRIVCMD_MMAP_RESOURCE
> 
> My recent Xen patch series introduces a new HYPERVISOR_memory_op to
> support direct priv-mapping of certain guest resources (such as ioreq
> pages, used by emulators) by a tools domain, rather than having to access
> such resources via the guest P2M.
> 
> This patch adds the necessary infrastructure to the privcmd driver and
> Xen MMU code to support direct resource mapping.
> 
> NOTE: The adjustment in the MMU code is partially cosmetic. Xen will now
>       allow a PV tools domain to map guest pages either by GFN or MFN, thus
>       the term 'gfn' has been swapped for 'pfn' in the lower layers of the
>       remap code.
> 
> Signed-off-by: Paul Durrant <paul.durrant@xxxxxxxxxx>

Unfortunately I have just found a bug in this patch when it comes to mapping 
multiple frames. I will send a v2 shortly. Apologies for the noise.

  Paul

> ---
> Cc: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
> Cc: Juergen Gross <jgross@xxxxxxxx>
> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> Cc: Ingo Molnar <mingo@xxxxxxxxxx>
> ---
>  arch/x86/xen/mmu.c             |  50 ++++++++++++-----
>  drivers/xen/privcmd.c          | 119
> +++++++++++++++++++++++++++++++++++++++++
>  include/uapi/xen/privcmd.h     |  11 ++++
>  include/xen/interface/memory.h |  67 +++++++++++++++++++++++
>  include/xen/interface/xen.h    |   7 +--
>  include/xen/xen-ops.h          |  24 ++++++++-
>  6 files changed, 260 insertions(+), 18 deletions(-)
> 
> diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
> index d33e7dbe3129..8453d7be415c 100644
> --- a/arch/x86/xen/mmu.c
> +++ b/arch/x86/xen/mmu.c
> @@ -65,37 +65,42 @@ static void xen_flush_tlb_all(void)
>  #define REMAP_BATCH_SIZE 16
> 
>  struct remap_data {
> -     xen_pfn_t *mfn;
> +     xen_pfn_t *pfn;
>       bool contiguous;
> +     bool no_translate;
>       pgprot_t prot;
>       struct mmu_update *mmu_update;
>  };
> 
> -static int remap_area_mfn_pte_fn(pte_t *ptep, pgtable_t token,
> +static int remap_area_pfn_pte_fn(pte_t *ptep, pgtable_t token,
>                                unsigned long addr, void *data)
>  {
>       struct remap_data *rmd = data;
> -     pte_t pte = pte_mkspecial(mfn_pte(*rmd->mfn, rmd->prot));
> +     pte_t pte = pte_mkspecial(mfn_pte(*rmd->pfn, rmd->prot));
> 
>       /* If we have a contiguous range, just update the mfn itself,
>          else update pointer to be "next mfn". */
>       if (rmd->contiguous)
> -             (*rmd->mfn)++;
> +             (*rmd->pfn)++;
>       else
> -             rmd->mfn++;
> +             rmd->pfn++;
> 
> -     rmd->mmu_update->ptr = virt_to_machine(ptep).maddr |
> MMU_NORMAL_PT_UPDATE;
> +     rmd->mmu_update->ptr = virt_to_machine(ptep).maddr;
> +     rmd->mmu_update->ptr |= rmd->no_translate ?
> +             MMU_PT_UPDATE_NO_TRANSLATE :
> +             MMU_NORMAL_PT_UPDATE;
>       rmd->mmu_update->val = pte_val_ma(pte);
>       rmd->mmu_update++;
> 
>       return 0;
>  }
> 
> -static int do_remap_gfn(struct vm_area_struct *vma,
> +static int do_remap_pfn(struct vm_area_struct *vma,
>                       unsigned long addr,
> -                     xen_pfn_t *gfn, int nr,
> +                     xen_pfn_t *pfn, int nr,
>                       int *err_ptr, pgprot_t prot,
> -                     unsigned domid,
> +                     unsigned int domid,
> +                     bool no_translate,
>                       struct page **pages)
>  {
>       int err = 0;
> @@ -106,11 +111,12 @@ static int do_remap_gfn(struct vm_area_struct
> *vma,
> 
>       BUG_ON(!((vma->vm_flags & (VM_PFNMAP | VM_IO)) ==
> (VM_PFNMAP | VM_IO)));
> 
> -     rmd.mfn = gfn;
> +     rmd.pfn = pfn;
>       rmd.prot = prot;
>       /* We use the err_ptr to indicate if there we are doing a contiguous
>        * mapping or a discontigious mapping. */
>       rmd.contiguous = !err_ptr;
> +     rmd.no_translate = no_translate;
> 
>       while (nr) {
>               int index = 0;
> @@ -121,7 +127,7 @@ static int do_remap_gfn(struct vm_area_struct *vma,
> 
>               rmd.mmu_update = mmu_update;
>               err = apply_to_page_range(vma->vm_mm, addr, range,
> -                                       remap_area_mfn_pte_fn, &rmd);
> +                                       remap_area_pfn_pte_fn, &rmd);
>               if (err)
>                       goto out;
> 
> @@ -175,7 +181,8 @@ int xen_remap_domain_gfn_range(struct
> vm_area_struct *vma,
>       if (xen_feature(XENFEAT_auto_translated_physmap))
>               return -EOPNOTSUPP;
> 
> -     return do_remap_gfn(vma, addr, &gfn, nr, NULL, prot, domid,
> pages);
> +     return do_remap_pfn(vma, addr, &gfn, nr, NULL, prot, domid, false,
> +                         pages);
>  }
>  EXPORT_SYMBOL_GPL(xen_remap_domain_gfn_range);
> 
> @@ -183,7 +190,7 @@ int xen_remap_domain_gfn_array(struct
> vm_area_struct *vma,
>                              unsigned long addr,
>                              xen_pfn_t *gfn, int nr,
>                              int *err_ptr, pgprot_t prot,
> -                            unsigned domid, struct page **pages)
> +                            unsigned int domid, struct page **pages)
>  {
>       if (xen_feature(XENFEAT_auto_translated_physmap))
>               return xen_xlate_remap_gfn_array(vma, addr, gfn, nr,
> err_ptr,
> @@ -194,10 +201,25 @@ int xen_remap_domain_gfn_array(struct
> vm_area_struct *vma,
>        * cause of "wrong memory was mapped in".
>        */
>       BUG_ON(err_ptr == NULL);
> -     return do_remap_gfn(vma, addr, gfn, nr, err_ptr, prot, domid,
> pages);
> +     return do_remap_pfn(vma, addr, gfn, nr, err_ptr, prot, domid,
> +                         false, pages);
>  }
>  EXPORT_SYMBOL_GPL(xen_remap_domain_gfn_array);
> 
> +int xen_remap_domain_mfn_array(struct vm_area_struct *vma,
> +                            unsigned long addr,
> +                            xen_pfn_t *mfn, int nr,
> +                            int *err_ptr, pgprot_t prot,
> +                            unsigned int domid, struct page **pages)
> +{
> +     if (xen_feature(XENFEAT_auto_translated_physmap))
> +             return -EOPNOTSUPP;
> +
> +     return do_remap_pfn(vma, addr, mfn, nr, err_ptr, prot, domid,
> +                         true, pages);
> +}
> +EXPORT_SYMBOL_GPL(xen_remap_domain_mfn_array);
> +
>  /* Returns: 0 success */
>  int xen_unmap_domain_gfn_range(struct vm_area_struct *vma,
>                              int nr, struct page **pages)
> diff --git a/drivers/xen/privcmd.c b/drivers/xen/privcmd.c
> index 1c909183c42a..e8b7e07658f2 100644
> --- a/drivers/xen/privcmd.c
> +++ b/drivers/xen/privcmd.c
> @@ -33,6 +33,7 @@
>  #include <xen/xen.h>
>  #include <xen/privcmd.h>
>  #include <xen/interface/xen.h>
> +#include <xen/interface/memory.h>
>  #include <xen/interface/hvm/dm_op.h>
>  #include <xen/features.h>
>  #include <xen/page.h>
> @@ -722,6 +723,120 @@ static long privcmd_ioctl_restrict(struct file *file,
> void __user *udata)
>       return 0;
>  }
> 
> +struct remap_pfn {
> +     struct mm_struct *mm;
> +     struct page **pages;
> +     pgprot_t prot;
> +     unsigned long i;
> +};
> +
> +static int remap_pfn(pte_t *ptep, pgtable_t token, unsigned long addr,
> +                  void *data)
> +{
> +     struct remap_pfn *r = data;
> +     struct page *page = r->pages[r->i];
> +     pte_t pte = pte_mkspecial(pfn_pte(page_to_pfn(page), r->prot));
> +
> +     set_pte_at(r->mm, addr, ptep, pte);
> +     r->i++;
> +
> +     return 0;
> +}
> +
> +static long privcmd_ioctl_mmap_resource(struct file *file, void __user
> *udata)
> +{
> +     struct privcmd_data *data = file->private_data;
> +     struct mm_struct *mm = current->mm;
> +     struct vm_area_struct *vma;
> +     struct privcmd_mmap_resource kdata;
> +     xen_pfn_t *pfns = NULL;
> +     struct xen_mem_acquire_resource xdata;
> +     int rc;
> +
> +     if (copy_from_user(&kdata, udata, sizeof(kdata)))
> +             return -EFAULT;
> +
> +     /* If restriction is in place, check the domid matches */
> +     if (data->domid != DOMID_INVALID && data->domid != kdata.dom)
> +             return -EPERM;
> +
> +     down_write(&mm->mmap_sem);
> +
> +     vma = find_vma(mm, kdata.addr);
> +     if (!vma || vma->vm_ops != &privcmd_vm_ops) {
> +             rc = -EINVAL;
> +             goto out;
> +     }
> +
> +     pfns = kcalloc(kdata.num, sizeof(*pfns), GFP_KERNEL);
> +     if (!pfns) {
> +             rc = -ENOMEM;
> +             goto out;
> +     }
> +
> +     if (xen_feature(XENFEAT_auto_translated_physmap)) {
> +             struct page **pages;
> +             unsigned int i;
> +
> +             rc = alloc_empty_pages(vma, kdata.num);
> +             if (rc < 0)
> +                     goto out;
> +
> +             pages = vma->vm_private_data;
> +             for (i = 0; i < kdata.num; i++) {
> +                     pfns[i] = page_to_pfn(pages[i]);
> +                     pr_info("pfn[%u] = %p\n", i, (void *)pfns[i]);
> +             }
> +     } else
> +             vma->vm_private_data = PRIV_VMA_LOCKED;
> +
> +     memset(&xdata, 0, sizeof(xdata));
> +     xdata.domid = kdata.dom;
> +     xdata.type = kdata.type;
> +     xdata.id = kdata.id;
> +     xdata.frame = kdata.idx;
> +     xdata.nr_frames = kdata.num;
> +     set_xen_guest_handle(xdata.frame_list, pfns);
> +
> +     xen_preemptible_hcall_begin();
> +     rc = HYPERVISOR_memory_op(XENMEM_acquire_resource,
> &xdata);
> +     xen_preemptible_hcall_end();
> +
> +     if (rc)
> +             goto out;
> +
> +     if (xen_feature(XENFEAT_auto_translated_physmap)) {
> +             struct remap_pfn r = {
> +                     .mm = vma->vm_mm,
> +                     .pages = vma->vm_private_data,
> +                     .prot = vma->vm_page_prot,
> +             };
> +
> +             rc = apply_to_page_range(r.mm, kdata.addr,
> +                                      kdata.num << PAGE_SHIFT,
> +                                      remap_pfn, &r);
> +     } else {
> +             unsigned int domid =
> +                     (xdata.flags & XENMEM_rsrc_acq_caller_owned) ?
> +                     DOMID_SELF : kdata.dom;
> +
> +             rc = xen_remap_domain_mfn_array(vma,
> +                                             kdata.addr & PAGE_MASK,
> +                                             pfns, kdata.num, NULL,
> +                                             vma->vm_page_prot,
> +                                             domid,
> +                                             vma->vm_private_data);
> +     }
> +
> +     rc = rc > 0 ? 0 : rc;
> +
> +out:
> +     kfree(pfns);
> +
> +     up_write(&mm->mmap_sem);
> +     return rc;
> +}
> +
>  static long privcmd_ioctl(struct file *file,
>                         unsigned int cmd, unsigned long data)
>  {
> @@ -753,6 +868,10 @@ static long privcmd_ioctl(struct file *file,
>               ret = privcmd_ioctl_restrict(file, udata);
>               break;
> 
> +     case IOCTL_PRIVCMD_MMAP_RESOURCE:
> +             ret = privcmd_ioctl_mmap_resource(file, udata);
> +             break;
> +
>       default:
>               break;
>       }
> diff --git a/include/uapi/xen/privcmd.h b/include/uapi/xen/privcmd.h
> index 39d3e7b8e993..d2029556083e 100644
> --- a/include/uapi/xen/privcmd.h
> +++ b/include/uapi/xen/privcmd.h
> @@ -89,6 +89,15 @@ struct privcmd_dm_op {
>       const struct privcmd_dm_op_buf __user *ubufs;
>  };
> 
> +struct privcmd_mmap_resource {
> +     domid_t dom;
> +     __u32 type;
> +     __u32 id;
> +     __u32 idx;
> +     __u64 num;
> +     __u64 addr;
> +};
> +
>  /*
>   * @cmd: IOCTL_PRIVCMD_HYPERCALL
>   * @arg: &privcmd_hypercall_t
> @@ -114,5 +123,7 @@ struct privcmd_dm_op {
>       _IOC(_IOC_NONE, 'P', 5, sizeof(struct privcmd_dm_op))
>  #define IOCTL_PRIVCMD_RESTRICT                                       \
>       _IOC(_IOC_NONE, 'P', 6, sizeof(domid_t))
> +#define IOCTL_PRIVCMD_MMAP_RESOURCE                          \
> +     _IOC(_IOC_NONE, 'P', 7, sizeof(struct privcmd_mmap_resource))
> 
>  #endif /* __LINUX_PUBLIC_PRIVCMD_H__ */
> diff --git a/include/xen/interface/memory.h
> b/include/xen/interface/memory.h
> index 583dd93b3016..b110142ea996 100644
> --- a/include/xen/interface/memory.h
> +++ b/include/xen/interface/memory.h
> @@ -265,4 +265,71 @@ struct xen_remove_from_physmap {
>  };
>  DEFINE_GUEST_HANDLE_STRUCT(xen_remove_from_physmap);
> 
> +/*
> + * Get the pages for a particular guest resource, so that they can be
> + * mapped directly by a tools domain.
> + */
> +#define XENMEM_acquire_resource 28
> +struct xen_mem_acquire_resource {
> +    /* IN - The domain whose resource is to be mapped */
> +    domid_t domid;
> +    /* IN - the type of resource */
> +    uint16_t type;
> +
> +#define XENMEM_resource_ioreq_server 0
> +#define XENMEM_resource_grant_table 1
> +
> +    /*
> +     * IN - a type-specific resource identifier, which must be zero
> +     *      unless stated otherwise.
> +     *
> +     * type == XENMEM_resource_ioreq_server -> id == ioreq server id
> +     * type == XENMEM_resource_grant_table -> id defined below
> +     */
> +    uint32_t id;
> +
> +#define XENMEM_resource_grant_table_id_shared 0
> +#define XENMEM_resource_grant_table_id_status 1
> +
> +    /* IN/OUT - As an IN parameter number of frames of the resource
> +     *          to be mapped. However, if the specified value is 0 and
> +     *          frame_list is NULL then this field will be set to the
> +     *          maximum value supported by the implementation on return.
> +     */
> +    uint32_t nr_frames;
> +    /*
> +     * OUT - Must be zero on entry. On return this may contain a bitwise
> +     *       OR of the following values.
> +     */
> +    uint32_t flags;
> +
> +    /* The resource pages have been assigned to the calling domain */
> +#define _XENMEM_rsrc_acq_caller_owned 0
> +#define XENMEM_rsrc_acq_caller_owned (1u <<
> _XENMEM_rsrc_acq_caller_owned)
> +
> +    /*
> +     * IN - the index of the initial frame to be mapped. This parameter
> +     *      is ignored if nr_frames is 0.
> +     */
> +    uint64_t frame;
> +
> +#define XENMEM_resource_ioreq_server_frame_bufioreq 0
> +#define XENMEM_resource_ioreq_server_frame_ioreq(n) (1 + (n))
> +
> +    /*
> +     * IN/OUT - If the tools domain is PV then, upon return, frame_list
> +     *          will be populated with the MFNs of the resource.
> +     *          If the tools domain is HVM then it is expected that, on
> +     *          entry, frame_list will be populated with a list of GFNs
> +     *          that will be mapped to the MFNs of the resource.
> +     *          If -EIO is returned then the frame_list has only been
> +     *          partially mapped and it is up to the caller to unmap all
> +     *          the GFNs.
> +     *          This parameter may be NULL if nr_frames is 0.
> +     */
> +    GUEST_HANDLE(xen_pfn_t) frame_list;
> +};
> +typedef struct xen_mem_acquire_resource
> xen_mem_acquire_resource_t;
> +DEFINE_GUEST_HANDLE_STRUCT(xen_mem_acquire_resource);
> +
>  #endif /* __XEN_PUBLIC_MEMORY_H__ */
> diff --git a/include/xen/interface/xen.h b/include/xen/interface/xen.h
> index 4f4830ef8f93..8bfb242f433e 100644
> --- a/include/xen/interface/xen.h
> +++ b/include/xen/interface/xen.h
> @@ -265,9 +265,10 @@
>   *
>   * PAT (bit 7 on) --> PWT (bit 3 on) and clear bit 7.
>   */
> -#define MMU_NORMAL_PT_UPDATE      0 /* checked '*ptr = val'. ptr is MA.
> */
> -#define MMU_MACHPHYS_UPDATE       1 /* ptr = MA of frame to modify
> entry for  */
> -#define MMU_PT_UPDATE_PRESERVE_AD 2 /* atomically: *ptr = val |
> (*ptr&(A|D)) */
> +#define MMU_NORMAL_PT_UPDATE       0 /* checked '*ptr = val'. ptr is
> MA.      */
> +#define MMU_MACHPHYS_UPDATE        1 /* ptr = MA of frame to modify
> entry for */
> +#define MMU_PT_UPDATE_PRESERVE_AD  2 /* atomically: *ptr = val |
> (*ptr&(A|D)) */
> +#define MMU_PT_UPDATE_NO_TRANSLATE 3 /* checked '*ptr = val'. ptr is
> MA.      */
> 
>  /*
>   * MMU EXTENDED OPERATIONS
> diff --git a/include/xen/xen-ops.h b/include/xen/xen-ops.h
> index fd23e42c6024..fd18c974a619 100644
> --- a/include/xen/xen-ops.h
> +++ b/include/xen/xen-ops.h
> @@ -63,7 +63,7 @@ static inline void
> xen_destroy_contiguous_region(phys_addr_t pstart,
>  struct vm_area_struct;
> 
>  /*
> - * xen_remap_domain_gfn_array() - map an array of foreign frames
> + * xen_remap_domain_gfn_array() - map an array of foreign frames by gfn
>   * @vma:     VMA to map the pages into
>   * @addr:    Address at which to map the pages
>   * @gfn:     Array of GFNs to map
> @@ -86,6 +86,28 @@ int xen_remap_domain_gfn_array(struct
> vm_area_struct *vma,
>                              unsigned domid,
>                              struct page **pages);
> 
> +/*
> + * xen_remap_domain_mfn_array() - map an array of foreign frames by
> mfn
> + * @vma:     VMA to map the pages into
> + * @addr:    Address at which to map the pages
> + * @mfn:     Array of MFNs to map
> + * @nr:      Number entries in the MFN array
> + * @err_ptr: Returns per-MFN error status.
> + * @prot:    page protection mask
> + * @domid:   Domain owning the pages
> + * @pages:   Array of pages if this domain has an auto-translated physmap
> + *
> + * @mfn and @err_ptr may point to the same buffer, the MFNs will be
> + * overwritten by the error codes after they are mapped.
> + *
> + * Returns the number of successfully mapped frames, or a -ve error
> + * code.
> + */
> +int xen_remap_domain_mfn_array(struct vm_area_struct *vma,
> +                            unsigned long addr, xen_pfn_t *mfn, int nr,
> +                            int *err_ptr, pgprot_t prot,
> +                            unsigned int domid, struct page **pages);
> +
>  /* xen_remap_domain_gfn_range() - map a range of foreign frames
>   * @vma:     VMA to map the pages into
>   * @addr:    Address at which to map the pages
> --
> 2.11.0


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