From 6f43ed01e87c8a8dbd8c826eaf0f714c1342c039 Mon Sep 17 00:00:00 2001 From: Nadav Amit Date: Tue, 15 Jul 2014 17:37:46 +0300 Subject: [PATCH] KVM: x86: DR6/7.RTM cannot be written Haswell and newer Intel CPUs have support for RTM, and in that case DR6.RTM is not fixed to 1 and DR7.RTM is not fixed to zero. That is not the case in the current KVM implementation. This bug is apparent only if the MOV-DR instruction is emulated or the host also debugs the guest. This patch is a partial fix which enables DR6.RTM and DR7.RTM to be cleared and set respectively. It also sets DR6.RTM upon every debug exception. Obviously, it is not a complete fix, as debugging of RTM is still unsupported. Signed-off-by: Nadav Amit Signed-off-by: Paolo Bonzini --- arch/x86/include/asm/kvm_host.h | 8 +++++--- arch/x86/kvm/cpuid.h | 8 ++++++++ arch/x86/kvm/vmx.c | 4 ++-- arch/x86/kvm/x86.c | 22 ++++++++++++++++------ 4 files changed, 31 insertions(+), 11 deletions(-) diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h index b8a4480176b9..a84eaf7ba33f 100644 --- a/arch/x86/include/asm/kvm_host.h +++ b/arch/x86/include/asm/kvm_host.h @@ -152,14 +152,16 @@ enum { #define DR6_BD (1 << 13) #define DR6_BS (1 << 14) -#define DR6_FIXED_1 0xffff0ff0 -#define DR6_VOLATILE 0x0000e00f +#define DR6_RTM (1 << 16) +#define DR6_FIXED_1 0xfffe0ff0 +#define DR6_INIT 0xffff0ff0 +#define DR6_VOLATILE 0x0001e00f #define DR7_BP_EN_MASK 0x000000ff #define DR7_GE (1 << 9) #define DR7_GD (1 << 13) #define DR7_FIXED_1 0x00000400 -#define DR7_VOLATILE 0xffff23ff +#define DR7_VOLATILE 0xffff2bff /* apic attention bits */ #define KVM_APIC_CHECK_VAPIC 0 diff --git a/arch/x86/kvm/cpuid.h b/arch/x86/kvm/cpuid.h index f9087315e0cd..a5380590ab0e 100644 --- a/arch/x86/kvm/cpuid.h +++ b/arch/x86/kvm/cpuid.h @@ -95,4 +95,12 @@ static inline bool guest_cpuid_has_gbpages(struct kvm_vcpu *vcpu) best = kvm_find_cpuid_entry(vcpu, 0x80000001, 0); return best && (best->edx & bit(X86_FEATURE_GBPAGES)); } + +static inline bool guest_cpuid_has_rtm(struct kvm_vcpu *vcpu) +{ + struct kvm_cpuid_entry2 *best; + + best = kvm_find_cpuid_entry(vcpu, 7, 0); + return best && (best->ebx & bit(X86_FEATURE_RTM)); +} #endif diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c index 3300f4f2da48..fd24f68378a7 100644 --- a/arch/x86/kvm/vmx.c +++ b/arch/x86/kvm/vmx.c @@ -4892,7 +4892,7 @@ static int handle_exception(struct kvm_vcpu *vcpu) if (!(vcpu->guest_debug & (KVM_GUESTDBG_SINGLESTEP | KVM_GUESTDBG_USE_HW_BP))) { vcpu->arch.dr6 &= ~15; - vcpu->arch.dr6 |= dr6; + vcpu->arch.dr6 |= dr6 | DR6_RTM; if (!(dr6 & ~DR6_RESERVED)) /* icebp */ skip_emulated_instruction(vcpu); @@ -5151,7 +5151,7 @@ static int handle_dr(struct kvm_vcpu *vcpu) return 0; } else { vcpu->arch.dr7 &= ~DR7_GD; - vcpu->arch.dr6 |= DR6_BD; + vcpu->arch.dr6 |= DR6_BD | DR6_RTM; vmcs_writel(GUEST_DR7, vcpu->arch.dr7); kvm_queue_exception(vcpu, DB_VECTOR); return 1; diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index cc4f65f39b87..08c48a3c7c3a 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -759,6 +759,15 @@ static void kvm_update_dr7(struct kvm_vcpu *vcpu) vcpu->arch.switch_db_regs |= KVM_DEBUGREG_BP_ENABLED; } +static u64 kvm_dr6_fixed(struct kvm_vcpu *vcpu) +{ + u64 fixed = DR6_FIXED_1; + + if (!guest_cpuid_has_rtm(vcpu)) + fixed |= DR6_RTM; + return fixed; +} + static int __kvm_set_dr(struct kvm_vcpu *vcpu, int dr, unsigned long val) { switch (dr) { @@ -774,7 +783,7 @@ static int __kvm_set_dr(struct kvm_vcpu *vcpu, int dr, unsigned long val) case 6: if (val & 0xffffffff00000000ULL) return -1; /* #GP */ - vcpu->arch.dr6 = (val & DR6_VOLATILE) | DR6_FIXED_1; + vcpu->arch.dr6 = (val & DR6_VOLATILE) | kvm_dr6_fixed(vcpu); kvm_update_dr6(vcpu); break; case 5: @@ -5115,7 +5124,8 @@ static void kvm_vcpu_check_singlestep(struct kvm_vcpu *vcpu, unsigned long rflag */ if (unlikely(rflags & X86_EFLAGS_TF)) { if (vcpu->guest_debug & KVM_GUESTDBG_SINGLESTEP) { - kvm_run->debug.arch.dr6 = DR6_BS | DR6_FIXED_1; + kvm_run->debug.arch.dr6 = DR6_BS | DR6_FIXED_1 | + DR6_RTM; kvm_run->debug.arch.pc = vcpu->arch.singlestep_rip; kvm_run->debug.arch.exception = DB_VECTOR; kvm_run->exit_reason = KVM_EXIT_DEBUG; @@ -5128,7 +5138,7 @@ static void kvm_vcpu_check_singlestep(struct kvm_vcpu *vcpu, unsigned long rflag * cleared by the processor". */ vcpu->arch.dr6 &= ~15; - vcpu->arch.dr6 |= DR6_BS; + vcpu->arch.dr6 |= DR6_BS | DR6_RTM; kvm_queue_exception(vcpu, DB_VECTOR); } } @@ -5147,7 +5157,7 @@ static bool kvm_vcpu_check_breakpoint(struct kvm_vcpu *vcpu, int *r) vcpu->arch.eff_db); if (dr6 != 0) { - kvm_run->debug.arch.dr6 = dr6 | DR6_FIXED_1; + kvm_run->debug.arch.dr6 = dr6 | DR6_FIXED_1 | DR6_RTM; kvm_run->debug.arch.pc = kvm_rip_read(vcpu) + get_segment_base(vcpu, VCPU_SREG_CS); @@ -5166,7 +5176,7 @@ static bool kvm_vcpu_check_breakpoint(struct kvm_vcpu *vcpu, int *r) if (dr6 != 0) { vcpu->arch.dr6 &= ~15; - vcpu->arch.dr6 |= dr6; + vcpu->arch.dr6 |= dr6 | DR6_RTM; kvm_queue_exception(vcpu, DB_VECTOR); *r = EMULATE_DONE; return true; @@ -6866,7 +6876,7 @@ void kvm_vcpu_reset(struct kvm_vcpu *vcpu) kvm_clear_exception_queue(vcpu); memset(vcpu->arch.db, 0, sizeof(vcpu->arch.db)); - vcpu->arch.dr6 = DR6_FIXED_1; + vcpu->arch.dr6 = DR6_INIT; kvm_update_dr6(vcpu); vcpu->arch.dr7 = DR7_FIXED_1; kvm_update_dr7(vcpu); -- 2.39.5