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Subject[PATCH 4.14 131/173] KVM: x86/mmu: Apply max PA check for MMIO sptes to 32-bit KVM
From: Sean Christopherson <>

[ Upstream commit e30a7d623dccdb3f880fbcad980b0cb589a1da45 ]

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 <>
Signed-off-by: Paolo Bonzini <>
Signed-off-by: Sasha Levin <>
arch/x86/kvm/x86.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index d915ea0e69cfd..d6851636edab3 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -6314,7 +6314,7 @@ 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) && maxphyaddr == 52)
+ if (maxphyaddr == 52)
mask &= ~1ull;

kvm_mmu_set_mmio_spte_mask(mask, mask);

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