@@ -159,11 +159,25 @@ static int gvt_pin_guest_page(struct intel_vgpu *vgpu, unsigned long gfn,
goto err;
}
- if (npage == 0)
- base_page = cur_page;
+ if (npage == 0) {
+ /*
+ * Bail immediately to avoid unnecessary pinning when
+ * trying to shadow a 2M page and the host page isn't
+ * a transparent hugepage.
+ *
+ * TODO: support other type hugepages, e.g. HugeTLB.
+ */
+ if (size == I915_GTT_PAGE_SIZE_2M &&
+ !PageTransHuge(cur_page))
+ ret = -EIO;
+ else
+ base_page = cur_page;
+ }
else if (base_page + npage != cur_page) {
gvt_vgpu_err("The pages are not continuous\n");
ret = -EINVAL;
+ }
+ if (ret < 0) {
npage++;
goto err;
}
When shadowing a GTT entry with a 2M page, explicitly verify that the first page pinned by VFIO is a transparent hugepage instead of assuming that page observed by is_2MB_gtt_possible() is the same page pinned by vfio_pin_pages(). E.g. if userspace is doing something funky with the guest's memslots, or if the page is demoted between is_2MB_gtt_possible() and vfio_pin_pages(). This is more of a performance optimization than a bug fix as the check for contiguous struct pages should guard against incorrect mapping (even though assuming struct pages are virtually contiguous is wrong). The real motivation for explicitly checking for a transparent hugepage after pinning is that it will reduce the risk of introducing a bug in a future fix for a page refcount leak (KVMGT doesn't put the reference acquired by gfn_to_pfn()), and eventually will allow KVMGT to stop using KVM's gfn_to_pfn() altogether. Signed-off-by: Sean Christopherson <seanjc@google.com> --- drivers/gpu/drm/i915/gvt/kvmgt.c | 18 ++++++++++++++++-- 1 file changed, 16 insertions(+), 2 deletions(-)