From 56d6efc2de5fcf76d3c7b33a7671bc04c53cb0e5 Mon Sep 17 00:00:00 2001 From: Feng Wu Date: Tue, 1 Apr 2014 17:46:33 +0800 Subject: KVM: Remove SMAP bit from CR4_RESERVED_BITS This patch removes SMAP bit from CR4_RESERVED_BITS. Signed-off-by: Feng Wu Signed-off-by: Marcelo Tosatti --- arch/x86/include/asm/kvm_host.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'arch') diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h index fcaf9c961265..7de069afb382 100644 --- a/arch/x86/include/asm/kvm_host.h +++ b/arch/x86/include/asm/kvm_host.h @@ -60,7 +60,7 @@ | X86_CR4_PSE | X86_CR4_PAE | X86_CR4_MCE \ | X86_CR4_PGE | X86_CR4_PCE | X86_CR4_OSFXSR | X86_CR4_PCIDE \ | X86_CR4_OSXSAVE | X86_CR4_SMEP | X86_CR4_FSGSBASE \ - | X86_CR4_OSXMMEXCPT | X86_CR4_VMXE)) + | X86_CR4_OSXMMEXCPT | X86_CR4_VMXE | X86_CR4_SMAP)) #define CR8_RESERVED_BITS (~(unsigned long)X86_CR8_TPR) -- cgit v1.2.2 From 97ec8c067d322d32effdc1701760d3babbc5595f Mon Sep 17 00:00:00 2001 From: Feng Wu Date: Tue, 1 Apr 2014 17:46:34 +0800 Subject: KVM: Add SMAP support when setting CR4 This patch adds SMAP handling logic when setting CR4 for guests Thanks a lot to Paolo Bonzini for his suggestion to use the branchless way to detect SMAP violation. Signed-off-by: Feng Wu Signed-off-by: Marcelo Tosatti --- arch/x86/kvm/cpuid.h | 8 ++++++++ arch/x86/kvm/mmu.c | 34 +++++++++++++++++++++++++++++++--- arch/x86/kvm/mmu.h | 44 ++++++++++++++++++++++++++++++++++++-------- arch/x86/kvm/paging_tmpl.h | 2 +- arch/x86/kvm/x86.c | 9 ++++++++- 5 files changed, 84 insertions(+), 13 deletions(-) (limited to 'arch') diff --git a/arch/x86/kvm/cpuid.h b/arch/x86/kvm/cpuid.h index a2a1bb7ed8c1..eeecbed26ac7 100644 --- a/arch/x86/kvm/cpuid.h +++ b/arch/x86/kvm/cpuid.h @@ -48,6 +48,14 @@ static inline bool guest_cpuid_has_smep(struct kvm_vcpu *vcpu) return best && (best->ebx & bit(X86_FEATURE_SMEP)); } +static inline bool guest_cpuid_has_smap(struct kvm_vcpu *vcpu) +{ + struct kvm_cpuid_entry2 *best; + + best = kvm_find_cpuid_entry(vcpu, 7, 0); + return best && (best->ebx & bit(X86_FEATURE_SMAP)); +} + static inline bool guest_cpuid_has_fsgsbase(struct kvm_vcpu *vcpu) { struct kvm_cpuid_entry2 *best; diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c index f5704d9e5ddc..084caf3efaf5 100644 --- a/arch/x86/kvm/mmu.c +++ b/arch/x86/kvm/mmu.c @@ -3601,20 +3601,27 @@ static void reset_rsvds_bits_mask_ept(struct kvm_vcpu *vcpu, } } -static void update_permission_bitmask(struct kvm_vcpu *vcpu, +void update_permission_bitmask(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu, bool ept) { unsigned bit, byte, pfec; u8 map; - bool fault, x, w, u, wf, uf, ff, smep; + bool fault, x, w, u, wf, uf, ff, smapf, cr4_smap, smep, smap = 0; smep = kvm_read_cr4_bits(vcpu, X86_CR4_SMEP); + cr4_smap = kvm_read_cr4_bits(vcpu, X86_CR4_SMAP); for (byte = 0; byte < ARRAY_SIZE(mmu->permissions); ++byte) { pfec = byte << 1; map = 0; wf = pfec & PFERR_WRITE_MASK; uf = pfec & PFERR_USER_MASK; ff = pfec & PFERR_FETCH_MASK; + /* + * PFERR_RSVD_MASK bit is set in PFEC if the access is not + * subject to SMAP restrictions, and cleared otherwise. The + * bit is only meaningful if the SMAP bit is set in CR4. + */ + smapf = !(pfec & PFERR_RSVD_MASK); for (bit = 0; bit < 8; ++bit) { x = bit & ACC_EXEC_MASK; w = bit & ACC_WRITE_MASK; @@ -3627,11 +3634,32 @@ static void update_permission_bitmask(struct kvm_vcpu *vcpu, w |= !is_write_protection(vcpu) && !uf; /* Disallow supervisor fetches of user code if cr4.smep */ x &= !(smep && u && !uf); + + /* + * SMAP:kernel-mode data accesses from user-mode + * mappings should fault. A fault is considered + * as a SMAP violation if all of the following + * conditions are ture: + * - X86_CR4_SMAP is set in CR4 + * - An user page is accessed + * - Page fault in kernel mode + * - if CPL = 3 or X86_EFLAGS_AC is clear + * + * Here, we cover the first three conditions. + * The fourth is computed dynamically in + * permission_fault() and is in smapf. + * + * Also, SMAP does not affect instruction + * fetches, add the !ff check here to make it + * clearer. + */ + smap = cr4_smap && u && !uf && !ff; } else /* Not really needed: no U/S accesses on ept */ u = 1; - fault = (ff && !x) || (uf && !u) || (wf && !w); + fault = (ff && !x) || (uf && !u) || (wf && !w) || + (smapf && smap); map |= fault << bit; } mmu->permissions[byte] = map; diff --git a/arch/x86/kvm/mmu.h b/arch/x86/kvm/mmu.h index 292615274358..3842e70bdb7c 100644 --- a/arch/x86/kvm/mmu.h +++ b/arch/x86/kvm/mmu.h @@ -44,11 +44,17 @@ #define PT_DIRECTORY_LEVEL 2 #define PT_PAGE_TABLE_LEVEL 1 -#define PFERR_PRESENT_MASK (1U << 0) -#define PFERR_WRITE_MASK (1U << 1) -#define PFERR_USER_MASK (1U << 2) -#define PFERR_RSVD_MASK (1U << 3) -#define PFERR_FETCH_MASK (1U << 4) +#define PFERR_PRESENT_BIT 0 +#define PFERR_WRITE_BIT 1 +#define PFERR_USER_BIT 2 +#define PFERR_RSVD_BIT 3 +#define PFERR_FETCH_BIT 4 + +#define PFERR_PRESENT_MASK (1U << PFERR_PRESENT_BIT) +#define PFERR_WRITE_MASK (1U << PFERR_WRITE_BIT) +#define PFERR_USER_MASK (1U << PFERR_USER_BIT) +#define PFERR_RSVD_MASK (1U << PFERR_RSVD_BIT) +#define PFERR_FETCH_MASK (1U << PFERR_FETCH_BIT) int kvm_mmu_get_spte_hierarchy(struct kvm_vcpu *vcpu, u64 addr, u64 sptes[4]); void kvm_mmu_set_mmio_spte_mask(u64 mmio_mask); @@ -73,6 +79,8 @@ int handle_mmio_page_fault_common(struct kvm_vcpu *vcpu, u64 addr, bool direct); void kvm_init_shadow_mmu(struct kvm_vcpu *vcpu, struct kvm_mmu *context); void kvm_init_shadow_ept_mmu(struct kvm_vcpu *vcpu, struct kvm_mmu *context, bool execonly); +void update_permission_bitmask(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu, + bool ept); static inline unsigned int kvm_mmu_available_pages(struct kvm *kvm) { @@ -110,10 +118,30 @@ static inline bool is_write_protection(struct kvm_vcpu *vcpu) * Will a fault with a given page-fault error code (pfec) cause a permission * fault with the given access (in ACC_* format)? */ -static inline bool permission_fault(struct kvm_mmu *mmu, unsigned pte_access, - unsigned pfec) +static inline bool permission_fault(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu, + unsigned pte_access, unsigned pfec) { - return (mmu->permissions[pfec >> 1] >> pte_access) & 1; + int cpl = kvm_x86_ops->get_cpl(vcpu); + unsigned long rflags = kvm_x86_ops->get_rflags(vcpu); + + /* + * If CPL < 3, SMAP prevention are disabled if EFLAGS.AC = 1. + * + * If CPL = 3, SMAP applies to all supervisor-mode data accesses + * (these are implicit supervisor accesses) regardless of the value + * of EFLAGS.AC. + * + * This computes (cpl < 3) && (rflags & X86_EFLAGS_AC), leaving + * the result in X86_EFLAGS_AC. We then insert it in place of + * the PFERR_RSVD_MASK bit; this bit will always be zero in pfec, + * but it will be one in index if SMAP checks are being overridden. + * It is important to keep this branchless. + */ + unsigned long smap = (cpl - 3) & (rflags & X86_EFLAGS_AC); + int index = (pfec >> 1) + + (smap >> (X86_EFLAGS_AC_BIT - PFERR_RSVD_BIT + 1)); + + return (mmu->permissions[index] >> pte_access) & 1; } void kvm_mmu_invalidate_zap_all_pages(struct kvm *kvm); diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h index b1e6c1bf68d3..123efd3ec29f 100644 --- a/arch/x86/kvm/paging_tmpl.h +++ b/arch/x86/kvm/paging_tmpl.h @@ -353,7 +353,7 @@ retry_walk: walker->ptes[walker->level - 1] = pte; } while (!is_last_gpte(mmu, walker->level, pte)); - if (unlikely(permission_fault(mmu, pte_access, access))) { + if (unlikely(permission_fault(vcpu, mmu, pte_access, access))) { errcode |= PFERR_PRESENT_MASK; goto error; } diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index d1c55f8722c6..41693787cd66 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -652,6 +652,9 @@ int kvm_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4) if (!guest_cpuid_has_smep(vcpu) && (cr4 & X86_CR4_SMEP)) return 1; + if (!guest_cpuid_has_smap(vcpu) && (cr4 & X86_CR4_SMAP)) + return 1; + if (!guest_cpuid_has_fsgsbase(vcpu) && (cr4 & X86_CR4_FSGSBASE)) return 1; @@ -680,6 +683,9 @@ int kvm_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4) (!(cr4 & X86_CR4_PCIDE) && (old_cr4 & X86_CR4_PCIDE))) kvm_mmu_reset_context(vcpu); + if ((cr4 ^ old_cr4) & X86_CR4_SMAP) + update_permission_bitmask(vcpu, vcpu->arch.walk_mmu, false); + if ((cr4 ^ old_cr4) & X86_CR4_OSXSAVE) kvm_update_cpuid(vcpu); @@ -4164,7 +4170,8 @@ static int vcpu_mmio_gva_to_gpa(struct kvm_vcpu *vcpu, unsigned long gva, | (write ? PFERR_WRITE_MASK : 0); if (vcpu_match_mmio_gva(vcpu, gva) - && !permission_fault(vcpu->arch.walk_mmu, vcpu->arch.access, access)) { + && !permission_fault(vcpu, vcpu->arch.walk_mmu, + vcpu->arch.access, access)) { *gpa = vcpu->arch.mmio_gfn << PAGE_SHIFT | (gva & (PAGE_SIZE - 1)); trace_vcpu_match_mmio(gva, *gpa, write, false); -- cgit v1.2.2 From e1e746b3c55d1d1e0841a2e600a154d8f6747232 Mon Sep 17 00:00:00 2001 From: Feng Wu Date: Tue, 1 Apr 2014 17:46:35 +0800 Subject: KVM: Disable SMAP for guests in EPT realmode and EPT unpaging mode SMAP is disabled if CPU is in non-paging mode in hardware. However KVM always uses paging mode to emulate guest non-paging mode with TDP. To emulate this behavior, SMAP needs to be manually disabled when guest switches to non-paging mode. Signed-off-by: Feng Wu Signed-off-by: Marcelo Tosatti --- arch/x86/kvm/vmx.c | 11 ++++++----- 1 file changed, 6 insertions(+), 5 deletions(-) (limited to 'arch') diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c index 1320e0f8e611..1f68c5831924 100644 --- a/arch/x86/kvm/vmx.c +++ b/arch/x86/kvm/vmx.c @@ -3484,13 +3484,14 @@ static int vmx_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4) hw_cr4 &= ~X86_CR4_PAE; hw_cr4 |= X86_CR4_PSE; /* - * SMEP is disabled if CPU is in non-paging mode in - * hardware. However KVM always uses paging mode to + * SMEP/SMAP is disabled if CPU is in non-paging mode + * in hardware. However KVM always uses paging mode to * emulate guest non-paging mode with TDP. - * To emulate this behavior, SMEP needs to be manually - * disabled when guest switches to non-paging mode. + * To emulate this behavior, SMEP/SMAP needs to be + * manually disabled when guest switches to non-paging + * mode. */ - hw_cr4 &= ~X86_CR4_SMEP; + hw_cr4 &= ~(X86_CR4_SMEP | X86_CR4_SMAP); } else if (!(cr4 & X86_CR4_PAE)) { hw_cr4 &= ~X86_CR4_PAE; } -- cgit v1.2.2 From de935ae15b0db57f7fb837b37380ee94d4b0fec3 Mon Sep 17 00:00:00 2001 From: Feng Wu Date: Tue, 1 Apr 2014 17:46:36 +0800 Subject: KVM: expose SMAP feature to guest This patch exposes SMAP feature to guest Signed-off-by: Feng Wu Signed-off-by: Marcelo Tosatti --- arch/x86/kvm/cpuid.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'arch') diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c index bea60671ef8a..f47a104a749c 100644 --- a/arch/x86/kvm/cpuid.c +++ b/arch/x86/kvm/cpuid.c @@ -308,7 +308,7 @@ static inline int __do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function, const u32 kvm_supported_word9_x86_features = F(FSGSBASE) | F(BMI1) | F(HLE) | F(AVX2) | F(SMEP) | F(BMI2) | F(ERMS) | f_invpcid | F(RTM) | f_mpx | F(RDSEED) | - F(ADX); + F(ADX) | F(SMAP); /* all calls to cpuid_count() should be made on the same cpu */ get_cpu(); -- cgit v1.2.2 From 66386ade2aa7f5fcf0dda4171df7b4d4c274d2d6 Mon Sep 17 00:00:00 2001 From: Feng Wu Date: Tue, 1 Apr 2014 17:56:48 +0800 Subject: KVM: Rename variable smep to cr4_smep Rename variable smep to cr4_smep, which can better reflect the meaning of the variable. Signed-off-by: Feng Wu Signed-off-by: Marcelo Tosatti --- arch/x86/kvm/mmu.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) (limited to 'arch') diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c index 084caf3efaf5..813d31038b93 100644 --- a/arch/x86/kvm/mmu.c +++ b/arch/x86/kvm/mmu.c @@ -3606,9 +3606,9 @@ void update_permission_bitmask(struct kvm_vcpu *vcpu, { unsigned bit, byte, pfec; u8 map; - bool fault, x, w, u, wf, uf, ff, smapf, cr4_smap, smep, smap = 0; + bool fault, x, w, u, wf, uf, ff, smapf, cr4_smap, cr4_smep, smap = 0; - smep = kvm_read_cr4_bits(vcpu, X86_CR4_SMEP); + cr4_smep = kvm_read_cr4_bits(vcpu, X86_CR4_SMEP); cr4_smap = kvm_read_cr4_bits(vcpu, X86_CR4_SMAP); for (byte = 0; byte < ARRAY_SIZE(mmu->permissions); ++byte) { pfec = byte << 1; @@ -3633,7 +3633,7 @@ void update_permission_bitmask(struct kvm_vcpu *vcpu, /* Allow supervisor writes if !cr0.wp */ w |= !is_write_protection(vcpu) && !uf; /* Disallow supervisor fetches of user code if cr4.smep */ - x &= !(smep && u && !uf); + x &= !(cr4_smep && u && !uf); /* * SMAP:kernel-mode data accesses from user-mode -- cgit v1.2.2 From b351c39cc9e0151cee9b8d52a1e714928faabb38 Mon Sep 17 00:00:00 2001 From: Marcelo Tosatti Date: Thu, 10 Apr 2014 18:19:12 -0300 Subject: KVM: x86: remove WARN_ON from get_kernel_ns() Function and callers can be preempted. https://bugzilla.kernel.org/show_bug.cgi?id=73721 Signed-off-by: Marcelo Tosatti Reviewed-by: Paolo Bonzini --- arch/x86/kvm/x86.c | 1 - 1 file changed, 1 deletion(-) (limited to 'arch') diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 41693787cd66..757d40871b30 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -1123,7 +1123,6 @@ static inline u64 get_kernel_ns(void) { struct timespec ts; - WARN_ON(preemptible()); ktime_get_ts(&ts); monotonic_to_bootbased(&ts); return timespec_to_ns(&ts); -- cgit v1.2.2