KVM: x86/mmu: Apply max PA check for MMIO sptes to 32-bit KVM

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")
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
[bwh: Backported to 3.16: adjust filename, context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index d516e0a4584a06d2357b3228100caebc14c6130e..c73ff06cbd71672bce6a60abc6d3116110f52ad7 100644 (file)
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -5734,7 +5734,7 @@ 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);