From: Sean Christopherson <[email protected]> commit 6129ed877d409037b79866327102c9dc59a302fe upstream.
Set the mmio_value to '0' instead of simply clearing the present bit to squash a benign warning in kvm_mmu_set_mmio_spte_mask() that complains about the mmio_value overlapping the lower GFN mask on systems with 52 bits of PA space. Opportunistically clean up the code and comments. Cc: [email protected] Fixes: d43e2675e96fc ("KVM: x86: only do L1TF workaround on affected processors") Signed-off-by: Sean Christopherson <[email protected]> Message-Id: <[email protected]> Signed-off-by: Paolo Bonzini <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]> --- arch/x86/kvm/mmu/mmu.c | 27 +++++++++------------------ 1 file changed, 9 insertions(+), 18 deletions(-) --- a/arch/x86/kvm/mmu/mmu.c +++ b/arch/x86/kvm/mmu/mmu.c @@ -6132,25 +6132,16 @@ static void kvm_set_mmio_spte_mask(void) u64 mask; /* - * Set the reserved bits and the present bit of an paging-structure - * entry to generate page fault with PFER.RSV = 1. + * Set a reserved PA bit in MMIO SPTEs to generate page faults with + * PFEC.RSVD=1 on MMIO accesses. 64-bit PTEs (PAE, x86-64, and EPT + * paging) support a maximum of 52 bits of PA, i.e. if the CPU supports + * 52-bit physical addresses then there are no reserved PA bits in the + * PTEs and so the reserved PA approach must be disabled. */ - - /* - * Mask the uppermost physical address bit, which would be reserved as - * long as the supported physical address width is less than 52. - */ - mask = 1ull << 51; - - /* Set the present bit. */ - mask |= 1ull; - - /* - * If reserved bit is not supported, clear the present bit to disable - * mmio page fault. - */ - if (shadow_phys_bits == 52) - mask &= ~1ull; + if (shadow_phys_bits < 52) + mask = BIT_ULL(51) | PT_PRESENT_MASK; + else + mask = 0; kvm_mmu_set_mmio_spte_mask(mask, mask, ACC_WRITE_MASK | ACC_USER_MASK); }
