From ea2800ddb20d6e66042051a61f66e6bea4fa0db7 Mon Sep 17 00:00:00 2001 From: Brijesh Singh Date: Fri, 25 Aug 2017 15:55:40 -0500 Subject: [PATCH] kvm/x86: Avoid clearing the C-bit in rsvd_bits() MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit The following commit: d0ec49d4de90 ("kvm/x86/svm: Support Secure Memory Encryption within KVM") uses __sme_clr() to remove the C-bit in rsvd_bits(). rsvd_bits() is just a simple function to return some 1 bits. Applying a mask based on properties of the host MMU is incorrect. Additionally, the masks computed by __reset_rsvds_bits_mask also apply to guest page tables, where the C bit is reserved since we don't emulate SME. The fix is to clear the C-bit from rsvd_bits_mask array after it has been populated from __reset_rsvds_bits_mask() Suggested-by: Paolo Bonzini Signed-off-by: Brijesh Singh Acked-by: Paolo Bonzini Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Radim Krčmář Cc: Stephen Rothwell Cc: Thomas Gleixner Cc: Tom Lendacky Cc: kvm@vger.kernel.org Cc: paolo.bonzini@gmail.com Fixes: d0ec49d ("kvm/x86/svm: Support Secure Memory Encryption within KVM") Link: http://lkml.kernel.org/r/20170825205540.123531-1-brijesh.singh@amd.com Signed-off-by: Ingo Molnar --- arch/x86/kvm/mmu.c | 30 +++++++++++++++++++++++++++--- arch/x86/kvm/mmu.h | 2 +- 2 files changed, 28 insertions(+), 4 deletions(-) diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c index ccb70b8d16cc..04d750813c9d 100644 --- a/arch/x86/kvm/mmu.c +++ b/arch/x86/kvm/mmu.c @@ -4109,16 +4109,28 @@ void reset_shadow_zero_bits_mask(struct kvm_vcpu *vcpu, struct kvm_mmu *context) { bool uses_nx = context->nx || context->base_role.smep_andnot_wp; + struct rsvd_bits_validate *shadow_zero_check; + int i; /* * Passing "true" to the last argument is okay; it adds a check * on bit 8 of the SPTEs which KVM doesn't use anyway. */ - __reset_rsvds_bits_mask(vcpu, &context->shadow_zero_check, + shadow_zero_check = &context->shadow_zero_check; + __reset_rsvds_bits_mask(vcpu, shadow_zero_check, boot_cpu_data.x86_phys_bits, context->shadow_root_level, uses_nx, guest_cpuid_has_gbpages(vcpu), is_pse(vcpu), true); + + if (!shadow_me_mask) + return; + + for (i = context->shadow_root_level; --i >= 0;) { + shadow_zero_check->rsvd_bits_mask[0][i] &= ~shadow_me_mask; + shadow_zero_check->rsvd_bits_mask[1][i] &= ~shadow_me_mask; + } + } EXPORT_SYMBOL_GPL(reset_shadow_zero_bits_mask); @@ -4136,17 +4148,29 @@ static void reset_tdp_shadow_zero_bits_mask(struct kvm_vcpu *vcpu, struct kvm_mmu *context) { + struct rsvd_bits_validate *shadow_zero_check; + int i; + + shadow_zero_check = &context->shadow_zero_check; + if (boot_cpu_is_amd()) - __reset_rsvds_bits_mask(vcpu, &context->shadow_zero_check, + __reset_rsvds_bits_mask(vcpu, shadow_zero_check, boot_cpu_data.x86_phys_bits, context->shadow_root_level, false, boot_cpu_has(X86_FEATURE_GBPAGES), true, true); else - __reset_rsvds_bits_mask_ept(&context->shadow_zero_check, + __reset_rsvds_bits_mask_ept(shadow_zero_check, boot_cpu_data.x86_phys_bits, false); + if (!shadow_me_mask) + return; + + for (i = context->shadow_root_level; --i >= 0;) { + shadow_zero_check->rsvd_bits_mask[0][i] &= ~shadow_me_mask; + shadow_zero_check->rsvd_bits_mask[1][i] &= ~shadow_me_mask; + } } /* diff --git a/arch/x86/kvm/mmu.h b/arch/x86/kvm/mmu.h index 3cc725590ab9..d7d248a000dd 100644 --- a/arch/x86/kvm/mmu.h +++ b/arch/x86/kvm/mmu.h @@ -48,7 +48,7 @@ static inline u64 rsvd_bits(int s, int e) { - return __sme_clr(((1ULL << (e - s + 1)) - 1) << s); + return ((1ULL << (e - s + 1)) - 1) << s; } void kvm_mmu_set_mmio_spte_mask(u64 mmio_mask, u64 mmio_value); -- 2.20.1