linux-kernel - [PATCH v3 03/28] drm/i915/gvt: Verify hugepages are contiguous in physical address space

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Message-ID: <20230513003600.818142-4-seanjc@google.com>
Date:   Fri, 12 May 2023 17:35:35 -0700
From:   Sean Christopherson <seanjc@...gle.com>
To:     Sean Christopherson <seanjc@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Zhenyu Wang <zhenyuw@...ux.intel.com>,
        Zhi Wang <zhi.a.wang@...el.com>
Cc:     kvm@...r.kernel.org, intel-gvt-dev@...ts.freedesktop.org,
        intel-gfx@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        Yan Zhao <yan.y.zhao@...el.com>,
        Ben Gardon <bgardon@...gle.com>
Subject: [PATCH v3 03/28] drm/i915/gvt: Verify hugepages are contiguous in
 physical address space

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=y", but not for "CONFIG_SPARSEMEM=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.

Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 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;
 			npage++;
-- 
2.40.1.606.ga4b1b128d6-goog