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* [PATCH] KVM: x86/mmu: Apply max PA check for MMIO sptes to 32-bit KVM
@ 2020-01-08  0:12 Sean Christopherson
  2020-01-15 18:20 ` Paolo Bonzini
  0 siblings, 1 reply; 2+ messages in thread
From: Sean Christopherson @ 2020-01-08  0:12 UTC (permalink / raw)
  To: Paolo Bonzini
  Cc: Sean Christopherson, Vitaly Kuznetsov, Wanpeng Li, Jim Mattson,
	Joerg Roedel, kvm, linux-kernel

Remove the bogus 64-bit only condition from the check that disables MMIO
spte optimization when the system supports the max PA, i.e. doesn't have
any reserved PA bits.  32-bit KVM always uses PAE paging for the shadow
MMU, and per Intel's SDM:

  PAE paging translates 32-bit linear addresses to 52-bit physical

The kernel's restrictions on max physical addresses are limits on how
much memory the kernel can reasonably use, not what physical addresses
are supported by hardware.

Fixes: ce88decffd17 ("KVM: MMU: mmio page fault support")
Signed-off-by: Sean Christopherson <>
 arch/x86/kvm/mmu/mmu.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 7269130ea5e2..d9c07343d979 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -6191,7 +6191,7 @@ static void kvm_set_mmio_spte_mask(void)
 	 * If reserved bit is not supported, clear the present bit to disable
 	 * mmio page fault.
-	if (IS_ENABLED(CONFIG_X86_64) && shadow_phys_bits == 52)
+	if (shadow_phys_bits == 52)
 		mask &= ~1ull;
 	kvm_mmu_set_mmio_spte_mask(mask, mask, ACC_WRITE_MASK | ACC_USER_MASK);

^ permalink raw reply	[flat|nested] 2+ messages in thread

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2020-01-08  0:12 [PATCH] KVM: x86/mmu: Apply max PA check for MMIO sptes to 32-bit KVM Sean Christopherson
2020-01-15 18:20 ` Paolo Bonzini

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