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Subject[PATCH 4.9 090/116] KVM: x86/mmu: Apply max PA check for MMIO sptes to 32-bit KVM
Date
From: Sean Christopherson <sean.j.christopherson@intel.com>

[ 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
addresses.

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")
Cc: stable@vger.kernel.org
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
arch/x86/kvm/x86.c | 2 --
1 file changed, 2 deletions(-)

--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -6132,14 +6132,12 @@ static void kvm_set_mmio_spte_mask(void)
/* Set the present bit. */
mask |= 1ull;

-#ifdef CONFIG_X86_64
/*
* If reserved bit is not supported, clear the present bit to disable
* mmio page fault.
*/
if (maxphyaddr == 52)
mask &= ~1ull;
-#endif

kvm_mmu_set_mmio_spte_mask(mask);
}

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