[Xen-devel] [RFC 22/23] xen/privcmd: Add support for Linux 64KB page granularity

[Julien Grall <julien.grall@xxxxxxxxxx>]

The hypercall interface (as well as the toolstack) is always using 4KB
page granularity. When the toolstack is asking for mapping a series of
guest PFN in a batch, it expects to have the page map contiguously in
its virtual memory.

When Linux is using 64KB page granularity, the privcmd driver will have
to map multiple Xen PFN in a single Linux page.

Note that this solution works on page granularity which is a multiple of
4KB.

Signed-off-by: Julien Grall <julien.grall@xxxxxxxxxx>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
Cc: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
Cc: David Vrabel <david.vrabel@xxxxxxxxxx>
---
 drivers/xen/privcmd.c   |  8 +++++---
 drivers/xen/xlate_mmu.c | 31 ++++++++++++++++++++-----------
 2 files changed, 25 insertions(+), 14 deletions(-)

diff --git a/drivers/xen/privcmd.c b/drivers/xen/privcmd.c
index 5a29616..e8714b4 100644
--- a/drivers/xen/privcmd.c
+++ b/drivers/xen/privcmd.c
@@ -446,7 +446,7 @@ static long privcmd_ioctl_mmap_batch(void __user *udata, 
int version)
                return -EINVAL;
        }
 
-       nr_pages = m.num;
+       nr_pages = DIV_ROUND_UP_ULL(m.num, PAGE_SIZE / XEN_PAGE_SIZE);
        if ((m.num <= 0) || (nr_pages > (LONG_MAX >> PAGE_SHIFT)))
                return -EINVAL;
 
@@ -494,7 +494,7 @@ static long privcmd_ioctl_mmap_batch(void __user *udata, 
int version)
                        goto out_unlock;
                }
                if (xen_feature(XENFEAT_auto_translated_physmap)) {
-                       ret = alloc_empty_pages(vma, m.num);
+                       ret = alloc_empty_pages(vma, nr_pages);
                        if (ret < 0)
                                goto out_unlock;
                } else
@@ -518,6 +518,7 @@ static long privcmd_ioctl_mmap_batch(void __user *udata, 
int version)
        state.global_error  = 0;
        state.version       = version;
 
+       BUILD_BUG_ON(((PAGE_SIZE / sizeof(xen_pfn_t)) % XEN_PFN_PER_PAGE) != 0);
        /* mmap_batch_fn guarantees ret == 0 */
        BUG_ON(traverse_pages_block(m.num, sizeof(xen_pfn_t),
                                    &pagelist, mmap_batch_fn, &state));
@@ -582,12 +583,13 @@ static void privcmd_close(struct vm_area_struct *vma)
 {
        struct page **pages = vma->vm_private_data;
        int numpgs = (vma->vm_end - vma->vm_start) >> PAGE_SHIFT;
+       int nr_pfn = (vma->vm_end - vma->vm_start) >> XEN_PAGE_SHIFT;
        int rc;
 
        if (!xen_feature(XENFEAT_auto_translated_physmap) || !numpgs || !pages)
                return;
 
-       rc = xen_unmap_domain_mfn_range(vma, numpgs, pages);
+       rc = xen_unmap_domain_mfn_range(vma, nr_pfn, pages);
        if (rc == 0)
                free_xenballooned_pages(numpgs, pages);
        else
diff --git a/drivers/xen/xlate_mmu.c b/drivers/xen/xlate_mmu.c
index 58a5389..b9dfe1b 100644
--- a/drivers/xen/xlate_mmu.c
+++ b/drivers/xen/xlate_mmu.c
@@ -63,6 +63,7 @@ static int map_foreign_page(unsigned long lpfn, unsigned long 
fgmfn,
 
 struct remap_data {
        xen_pfn_t *fgmfn; /* foreign domain's gmfn */
+       xen_pfn_t *egmfn; /* end foreign domain's gmfn */
        pgprot_t prot;
        domid_t  domid;
        struct vm_area_struct *vma;
@@ -78,17 +79,23 @@ static int remap_pte_fn(pte_t *ptep, pgtable_t token, 
unsigned long addr,
 {
        struct remap_data *info = data;
        struct page *page = info->pages[info->index++];
-       unsigned long pfn = page_to_pfn(page);
-       pte_t pte = pte_mkspecial(pfn_pte(pfn, info->prot));
+       unsigned long pfn = xen_page_to_pfn(page);
+       pte_t pte = pte_mkspecial(pfn_pte(page_to_pfn(page), info->prot));
        int rc;
-
-       rc = map_foreign_page(pfn, *info->fgmfn, info->domid);
-       *info->err_ptr++ = rc;
-       if (!rc) {
-               set_pte_at(info->vma->vm_mm, addr, ptep, pte);
-               info->mapped++;
+       uint32_t i;
+
+       for (i = 0; i < XEN_PFN_PER_PAGE; i++) {
+               if (info->fgmfn == info->egmfn)
+                       break;
+
+               rc = map_foreign_page(pfn++, *info->fgmfn, info->domid);
+               *info->err_ptr++ = rc;
+               if (!rc) {
+                       set_pte_at(info->vma->vm_mm, addr, ptep, pte);
+                       info->mapped++;
+               }
+               info->fgmfn++;
        }
-       info->fgmfn++;
 
        return 0;
 }
@@ -102,13 +109,14 @@ int xen_xlate_remap_gfn_array(struct vm_area_struct *vma,
 {
        int err;
        struct remap_data data;
-       unsigned long range = nr << PAGE_SHIFT;
+       unsigned long range = round_up(nr, XEN_PFN_PER_PAGE) << XEN_PAGE_SHIFT;
 
        /* Kept here for the purpose of making sure code doesn't break
           x86 PVOPS */
        BUG_ON(!((vma->vm_flags & (VM_PFNMAP | VM_IO)) == (VM_PFNMAP | VM_IO)));
 
        data.fgmfn = mfn;
+       data.egmfn = mfn + nr;
        data.prot  = prot;
        data.domid = domid;
        data.vma   = vma;
@@ -132,7 +140,8 @@ int xen_xlate_unmap_gfn_range(struct vm_area_struct *vma,
                struct xen_remove_from_physmap xrp;
                unsigned long pfn;
 
-               pfn = page_to_pfn(pages[i]);
+               pfn = xen_page_to_pfn(pages[i / XEN_PFN_PER_PAGE]) +
+                       (i % XEN_PFN_PER_PAGE);
 
                xrp.domid = DOMID_SELF;
                xrp.gpfn = pfn;
-- 
2.1.4


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