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authorSean Christopherson <seanjc@google.com>2022-04-29 01:04:09 +0000
committerPaolo Bonzini <pbonzini@redhat.com>2022-06-20 06:21:31 -0400
commita1040b0d42acf69bb4f6dbdc54c2dcd78eea1de5 (patch)
tree666224b6dacea24df002e09d3e1bbebb676b3471 /virt
parent28b85ae06f64bf1c1adea68a2fbb31dc40cc060e (diff)
KVM: Don't set Accessed/Dirty bits for ZERO_PAGE
Don't set Accessed/Dirty bits for a struct page with PG_reserved set, i.e. don't set A/D bits for the ZERO_PAGE. The ZERO_PAGE (or pages depending on the architecture) should obviously never be written, and similarly there's no point in marking it accessed as the page will never be swapped out or reclaimed. The comment in page-flags.h is quite clear that PG_reserved pages should be managed only by their owner, and strictly following that mandate also simplifies KVM's logic. Fixes: 7df003c85218 ("KVM: fix overflow of zero page refcount with ksm running") Signed-off-by: Sean Christopherson <seanjc@google.com> Message-Id: <20220429010416.2788472-4-seanjc@google.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'virt')
-rw-r--r--virt/kvm/kvm_main.c16
1 files changed, 14 insertions, 2 deletions
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 8f475d174e3d..351cbd121cf5 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -2850,16 +2850,28 @@ void kvm_release_pfn_dirty(kvm_pfn_t pfn)
}
EXPORT_SYMBOL_GPL(kvm_release_pfn_dirty);
+static bool kvm_is_ad_tracked_pfn(kvm_pfn_t pfn)
+{
+ if (!pfn_valid(pfn))
+ return false;
+
+ /*
+ * Per page-flags.h, pages tagged PG_reserved "should in general not be
+ * touched (e.g. set dirty) except by its owner".
+ */
+ return !PageReserved(pfn_to_page(pfn));
+}
+
void kvm_set_pfn_dirty(kvm_pfn_t pfn)
{
- if (!kvm_is_reserved_pfn(pfn) && !kvm_is_zone_device_pfn(pfn))
+ if (kvm_is_ad_tracked_pfn(pfn))
SetPageDirty(pfn_to_page(pfn));
}
EXPORT_SYMBOL_GPL(kvm_set_pfn_dirty);
void kvm_set_pfn_accessed(kvm_pfn_t pfn)
{
- if (!kvm_is_reserved_pfn(pfn) && !kvm_is_zone_device_pfn(pfn))
+ if (kvm_is_ad_tracked_pfn(pfn))
mark_page_accessed(pfn_to_page(pfn));
}
EXPORT_SYMBOL_GPL(kvm_set_pfn_accessed);