RE: [PATCH v5] xen/privcmd: add IOCTL_PRIVCMD_MMAP_RESOURCE

[Paul Durrant]

Apoligies. I appear to have already sent this a while ago.

  Paul

> -----Original Message-----
> From: Paul Durrant [mailto:paul.durrant@xxxxxxxxxx]
> Sent: 09 May 2018 14:16
> To: xen-devel@xxxxxxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; linux-
> arm-kernel@xxxxxxxxxxxxxxxxxxx
> Cc: Paul Durrant <Paul.Durrant@xxxxxxxxxx>; Juergen Gross
> <jgross@xxxxxxxx>; Thomas Gleixner <tglx@xxxxxxxxxxxxx>; Ingo Molnar
> <mingo@xxxxxxxxxx>; Stefano Stabellini <sstabellini@xxxxxxxxxx>
> Subject: [PATCH v5] 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 'mfn' has been swapped for 'pfn' in the lower layers of the
>       remap code.
> 
> Signed-off-by: Paul Durrant <paul.durrant@xxxxxxxxxx>
> Reviewed-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
> ---
> Cc: Juergen Gross <jgross@xxxxxxxx>
> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> Cc: Ingo Molnar <mingo@xxxxxxxxxx>
> Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx>
> 
> v5:
>  - Handle the case of xen_feature(XENFEAT_auto_translated_physmap) &&
>    (PAGE_SIZE > XEN_PAGE_SIZE)
> 
> v4:
>  - Remove stray line of debug that causes a build warning on ARM 32-bit
> 
> v3:
>  - Addres comments from Boris
>  - Fix ARM build
> 
> v2:
>  - Fix bug when mapping multiple pages of a resource
> ---
>  arch/arm/xen/enlighten.c       |  11 ++++
>  arch/x86/xen/mmu.c             |  60 +++++++++++++------
>  drivers/xen/privcmd.c          | 133
> +++++++++++++++++++++++++++++++++++++++++
>  include/uapi/xen/privcmd.h     |  11 ++++
>  include/xen/interface/memory.h |  66 ++++++++++++++++++++
>  include/xen/interface/xen.h    |   7 ++-
>  include/xen/xen-ops.h          |  24 +++++++-
>  7 files changed, 291 insertions(+), 21 deletions(-)
> 
> diff --git a/arch/arm/xen/enlighten.c b/arch/arm/xen/enlighten.c
> index ba7f4c8f5c3e..8073625371f5 100644
> --- a/arch/arm/xen/enlighten.c
> +++ b/arch/arm/xen/enlighten.c
> @@ -89,6 +89,17 @@ int xen_unmap_domain_gfn_range(struct
> vm_area_struct *vma,
>  }
>  EXPORT_SYMBOL_GPL(xen_unmap_domain_gfn_range);
> 
> +/* Not used by XENFEAT_auto_translated guests. */
> +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)
> +{
> +	return -ENOSYS;
> +}
> +EXPORT_SYMBOL_GPL(xen_remap_domain_mfn_array);
> +
>  static void xen_read_wallclock(struct timespec64 *ts)
>  {
>  	u32 version;
> diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
> index d33e7dbe3129..af2960cb7a3e 100644
> --- a/arch/x86/xen/mmu.c
> +++ b/arch/x86/xen/mmu.c
> @@ -65,37 +65,44 @@ 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 we have a contiguous range, just update the pfn itself,
> +	 * else update pointer to be "next pfn".
> +	 */
>  	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 +113,14 @@ 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. */
> +	/*
> +	 * 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 +131,7 @@ 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 +185,8 @@ 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);
> 
> @@ -194,10 +205,25 @@ 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..a7a2286d101a 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 +723,134 @@ 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_fn(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)) {
> +		unsigned int nr = DIV_ROUND_UP(kdata.num,
> XEN_PFN_PER_PAGE);
> +		struct page **pages;
> +		unsigned int i;
> +
> +		rc = alloc_empty_pages(vma, nr);
> +		if (rc < 0)
> +			goto out;
> +
> +		pages = vma->vm_private_data;
> +		for (i = 0; i < kdata.num; i++) {
> +			xen_pfn_t pfn =
> +				page_to_xen_pfn(pages[i /
> XEN_PFN_PER_PAGE]);
> +
> +			pfns[i] = pfn + (i % XEN_PFN_PER_PAGE);
> +		}
> +	} 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_fn, &r);
> +	} else {
> +		unsigned int domid =
> +			(xdata.flags & XENMEM_rsrc_acq_caller_owned) ?
> +			DOMID_SELF : kdata.dom;
> +		int num;
> +
> +		num = xen_remap_domain_mfn_array(vma,
> +						 kdata.addr & PAGE_MASK,
> +						 pfns, kdata.num, (int *)pfns,
> +						 vma->vm_page_prot,
> +						 domid,
> +						 vma->vm_private_data);
> +		if (num < 0)
> +			rc = num;
> +		else if (num != kdata.num) {
> +			unsigned int i;
> +
> +			for (i = 0; i < num; i++) {
> +				rc = pfns[i];
> +				if (rc < 0)
> +					break;
> +			}
> +		} else
> +			rc = 0;
> +	}
> +
> +out:
> +	up_write(&mm->mmap_sem);
> +	kfree(pfns);
> +
> +	return rc;
> +}
> +
>  static long privcmd_ioctl(struct file *file,
>  			  unsigned int cmd, unsigned long data)
>  {
> @@ -753,6 +882,10 @@ 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..4c5751c26f87 100644
> --- a/include/xen/interface/memory.h
> +++ b/include/xen/interface/memory.h
> @@ -265,4 +265,70 @@ 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;
> +};
> +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