[PATCH 5.5 243/367] KVM: x86/mmu: Apply max PA check for MMIO sptes to 32-bit KVM

Greg Kroah-Hartman
2020-02-10T12:58:51Z

From: Sean Christopherson <sean.j.christopherson@intel.com>

commit e30a7d623dccdb3f880fbcad980b0cb589a1da45 upstream.

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: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
arch/x86/kvm/mmu/mmu.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -6249,7 +6249,7 @@ 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);