Re: [PATCH v4 03/29] drm/i915/gvt: Verify hugepages are contiguous in physical address space

From: Wang, Zhi A
Date: Tue Aug 01 2023 - 07:24:10 EST

On 8/1/2023 4:47 AM, Yan Zhao wrote:
Reviewed-by: Yan Zhao <yan.y.zhao@xxxxxxxxx>

On Fri, Jul 28, 2023 at 06:35:09PM -0700, Sean Christopherson wrote:
When shadowing a GTT entry with a 2M page, verify that the pfns are
contiguous, not just that the struct page pointers are contiguous. The
memory map is virtual contiguous if "CONFIG_FLATMEM=y ||
CONFIG_SPARSEMEM_VMEMMAP=n", so theoretically KVMGT could encounter struct
pages that are virtually contiguous, but not physically contiguous.

In practice, this flaw is likely a non-issue as it would cause functional
problems iff a section isn't 2M aligned _and_ is directly adjacent to
another section with discontiguous pfns.

Tested-by: Yongwei Ma <>
Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
drivers/gpu/drm/i915/gvt/kvmgt.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/gvt/kvmgt.c b/drivers/gpu/drm/i915/gvt/kvmgt.c
index de675d799c7d..429f0f993a13 100644
--- a/drivers/gpu/drm/i915/gvt/kvmgt.c
+++ b/drivers/gpu/drm/i915/gvt/kvmgt.c
@@ -161,7 +161,7 @@ static int gvt_pin_guest_page(struct intel_vgpu *vgpu, unsigned long gfn,
if (npage == 0)
base_page = cur_page;
- else if (base_page + npage != cur_page) {
+ else if (page_to_pfn(base_page) + npage != page_to_pfn(cur_page)) {
gvt_vgpu_err("The pages are not continuous\n");
ret = -EINVAL;

Reviewed-by: Zhi Wang <>