To avoid breaking the CPUs without bus lock detection, activate the DR6_BUS_LOCK bit (bit 11) conditionally in DR6_FIXED_1 bits. The set/clear of DR6_BUS_LOCK is similar to the DR6_RTM in DR6 register. The processor clears DR6_BUS_LOCK when bus lock debug exception is generated. (For all other #DB the processor sets this bit to 1.) Software #DB handler should set this bit before returning to the interrupted task. For VM exit caused by debug exception, bit 11 of the exit qualification is set to indicate that a bus lock debug exception condition was detected. The VMM should emulate the exception by clearing bit 11 of the guest DR6. Co-developed-by: Xiaoyao Li <xiaoyao.li@xxxxxxxxx> Signed-off-by: Xiaoyao Li <xiaoyao.li@xxxxxxxxx> Signed-off-by: Chenyi Qiang <chenyi.qiang@xxxxxxxxx> --- arch/x86/include/asm/kvm_host.h | 5 +++-- arch/x86/kvm/emulate.c | 2 +- arch/x86/kvm/svm/svm.c | 6 +++--- arch/x86/kvm/vmx/nested.c | 2 +- arch/x86/kvm/vmx/vmx.c | 6 ++++-- arch/x86/kvm/x86.c | 28 +++++++++++++++++----------- 6 files changed, 29 insertions(+), 20 deletions(-) diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h index 3ab7b46087b7..826fd1e87352 100644 --- a/arch/x86/include/asm/kvm_host.h +++ b/arch/x86/include/asm/kvm_host.h @@ -196,13 +196,14 @@ enum x86_intercept_stage; #define KVM_NR_DB_REGS 4 +#define DR6_BUS_LOCK (1 << 11) #define DR6_BD (1 << 13) #define DR6_BS (1 << 14) #define DR6_BT (1 << 15) #define DR6_RTM (1 << 16) -#define DR6_FIXED_1 0xfffe0ff0 +#define DR6_FIXED_1 0xfffe07f0 #define DR6_INIT 0xffff0ff0 -#define DR6_VOLATILE 0x0001e00f +#define DR6_VOLATILE 0x0001e80f #define DR7_BP_EN_MASK 0x000000ff #define DR7_GE (1 << 9) diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c index 56cae1ff9e3f..882598da20f0 100644 --- a/arch/x86/kvm/emulate.c +++ b/arch/x86/kvm/emulate.c @@ -4327,7 +4327,7 @@ static int check_dr_read(struct x86_emulate_ctxt *ctxt) ctxt->ops->get_dr(ctxt, 6, &dr6); dr6 &= ~DR_TRAP_BITS; - dr6 |= DR6_BD | DR6_RTM; + dr6 |= DR6_BD | DR6_RTM | DR6_BUS_LOCK; ctxt->ops->set_dr(ctxt, 6, dr6); return emulate_db(ctxt); } diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c index cce0143a6f80..3d8a0e30314f 100644 --- a/arch/x86/kvm/svm/svm.c +++ b/arch/x86/kvm/svm/svm.c @@ -1860,7 +1860,7 @@ static void svm_sync_dirty_debug_regs(struct kvm_vcpu *vcpu) get_debugreg(vcpu->arch.db[2], 2); get_debugreg(vcpu->arch.db[3], 3); /* - * We cannot reset svm->vmcb->save.dr6 to DR6_FIXED_1|DR6_RTM here, + * We cannot reset svm->vmcb->save.dr6 to DR6_FIXED_1|DR6_RTM|DR6_BUS_LOCK here, * because db_interception might need it. We can do it before vmentry. */ vcpu->arch.dr6 = svm->vmcb->save.dr6; @@ -1911,7 +1911,7 @@ static int db_interception(struct vcpu_svm *svm) if (!(svm->vcpu.guest_debug & (KVM_GUESTDBG_SINGLESTEP | KVM_GUESTDBG_USE_HW_BP)) && !svm->nmi_singlestep) { - u32 payload = (svm->vmcb->save.dr6 ^ DR6_RTM) & ~DR6_FIXED_1; + u32 payload = (svm->vmcb->save.dr6 ^ (DR6_RTM|DR6_BUS_LOCK)) & ~DR6_FIXED_1; kvm_queue_exception_p(&svm->vcpu, DB_VECTOR, payload); return 1; } @@ -3778,7 +3778,7 @@ static __no_kcsan fastpath_t svm_vcpu_run(struct kvm_vcpu *vcpu) if (unlikely(svm->vcpu.arch.switch_db_regs & KVM_DEBUGREG_WONT_EXIT)) svm_set_dr6(svm, vcpu->arch.dr6); else - svm_set_dr6(svm, DR6_FIXED_1 | DR6_RTM); + svm_set_dr6(svm, DR6_FIXED_1 | DR6_RTM | DR6_BUS_LOCK); clgi(); kvm_load_guest_xsave_state(vcpu); diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c index e2f26564a12d..c5d71a9b3729 100644 --- a/arch/x86/kvm/vmx/nested.c +++ b/arch/x86/kvm/vmx/nested.c @@ -412,7 +412,7 @@ static int nested_vmx_check_exception(struct kvm_vcpu *vcpu, unsigned long *exit if (!has_payload) { payload = vcpu->arch.dr6; payload &= ~(DR6_FIXED_1 | DR6_BT); - payload ^= DR6_RTM; + payload ^= DR6_RTM | DR6_BUS_LOCK; } *exit_qual = payload; } else diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c index 75c9c6a0a3a4..13c9bcc4d9d9 100644 --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -4824,7 +4824,8 @@ static int handle_exception_nmi(struct kvm_vcpu *vcpu) kvm_queue_exception_p(vcpu, DB_VECTOR, dr6); return 1; } - kvm_run->debug.arch.dr6 = dr6 | DR6_FIXED_1 | DR6_RTM; + kvm_run->debug.arch.dr6 = dr6 | DR6_FIXED_1 | DR6_RTM | + DR6_BUS_LOCK; kvm_run->debug.arch.dr7 = vmcs_readl(GUEST_DR7); fallthrough; case BP_VECTOR: @@ -5068,7 +5069,8 @@ static int handle_dr(struct kvm_vcpu *vcpu) * guest debugging itself. */ if (vcpu->guest_debug & KVM_GUESTDBG_USE_HW_BP) { - vcpu->run->debug.arch.dr6 = DR6_BD | DR6_RTM | DR6_FIXED_1; + vcpu->run->debug.arch.dr6 = DR6_BD | DR6_RTM | DR6_FIXED_1 | + DR6_BUS_LOCK; vcpu->run->debug.arch.dr7 = dr7; vcpu->run->debug.arch.pc = kvm_get_linear_rip(vcpu); vcpu->run->debug.arch.exception = DB_VECTOR; diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 3f7c1fc7a3ce..06de2b9e57f3 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -483,19 +483,20 @@ void kvm_deliver_exception_payload(struct kvm_vcpu *vcpu) */ vcpu->arch.dr6 &= ~DR_TRAP_BITS; /* - * DR6.RTM is set by all #DB exceptions that don't clear it. + * DR6.RTM and DR6.BUS_LOCK are set by all #DB exceptions + * that don't clear it. */ - vcpu->arch.dr6 |= DR6_RTM; + vcpu->arch.dr6 |= DR6_RTM | DR6_BUS_LOCK; vcpu->arch.dr6 |= payload; /* - * Bit 16 should be set in the payload whenever the #DB - * exception should clear DR6.RTM. This makes the payload - * compatible with the pending debug exceptions under VMX. - * Though not currently documented in the SDM, this also - * makes the payload compatible with the exit qualification - * for #DB exceptions under VMX. + * Bit 16/Bit 11 should be set in the payload whenever + * the #DB exception should clear DR6.RTM/DR6.BUS_LOCK. + * This makes the payload compatible with the pending debug + * exceptions under VMX. Though not currently documented in + * the SDM, this also makes the payload compatible with the + * exit qualification for #DB exceptions under VMX. */ - vcpu->arch.dr6 ^= payload & DR6_RTM; + vcpu->arch.dr6 ^= payload & (DR6_RTM | DR6_BUS_LOCK); /* * The #DB payload is defined as compatible with the 'pending @@ -1126,6 +1127,9 @@ static u64 kvm_dr6_fixed(struct kvm_vcpu *vcpu) if (!guest_cpuid_has(vcpu, X86_FEATURE_RTM)) fixed |= DR6_RTM; + + if (!guest_cpuid_has(vcpu, X86_FEATURE_BUS_LOCK_DETECT)) + fixed |= DR6_BUS_LOCK; return fixed; } @@ -7197,7 +7201,8 @@ static int kvm_vcpu_do_singlestep(struct kvm_vcpu *vcpu) struct kvm_run *kvm_run = vcpu->run; if (vcpu->guest_debug & KVM_GUESTDBG_SINGLESTEP) { - kvm_run->debug.arch.dr6 = DR6_BS | DR6_FIXED_1 | DR6_RTM; + kvm_run->debug.arch.dr6 = DR6_BS | DR6_FIXED_1 | DR6_RTM | + DR6_BUS_LOCK; kvm_run->debug.arch.pc = kvm_get_linear_rip(vcpu); kvm_run->debug.arch.exception = DB_VECTOR; kvm_run->exit_reason = KVM_EXIT_DEBUG; @@ -7241,7 +7246,8 @@ 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 | DR6_RTM; + kvm_run->debug.arch.dr6 = dr6 | DR6_FIXED_1 | DR6_RTM | + DR6_BUS_LOCK; kvm_run->debug.arch.pc = eip; kvm_run->debug.arch.exception = DB_VECTOR; kvm_run->exit_reason = KVM_EXIT_DEBUG; -- 2.17.1