From: Sean Christopherson Date: Wed, 27 May 2020 01:49:09 -0700 Subject: KVM: x86/mmu: Set mmio_value to '0' if reserved #PF can't be generated Git-commit: 6129ed877d409037b79866327102c9dc59a302fe Patch-mainline: v5.8-rc1 References: bsc#1171904 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: stable@vger.kernel.org Fixes: d43e2675e96fc ("KVM: x86: only do L1TF workaround on affected processors") Signed-off-by: Sean Christopherson Message-Id: <20200527084909.23492-1-sean.j.christopherson@intel.com> Signed-off-by: Paolo Bonzini Acked-by: Joerg Roedel --- arch/x86/kvm/mmu/mmu.c | 27 +++++++++------------------ 1 file changed, 9 insertions(+), 18 deletions(-) --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -6300,25 +6300,17 @@ static void kvm_set_mmio_spte_mask(void) int maxphyaddr = boot_cpu_data.x86_phys_bits; /* - * 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 (IS_ENABLED(CONFIG_X86_64) && maxphyaddr == 52) - mask &= ~1ull; + if (maxphyaddr < 52) + mask = BIT_ULL(51) | PT_PRESENT_MASK; + else + mask = 0; kvm_mmu_set_mmio_spte_mask(mask, mask); }