From 18d609bb0b8c6823a750b32106be5685ca3daff7 Mon Sep 17 00:00:00 2001 From: Paolo Bonzini Date: Fri, 26 Feb 2016 12:28:40 +0100 Subject: [PATCH] KVM: x86: fix root cause for missed hardware breakpoints [ Upstream commit 70e4da7a8ff62f2775337b705f45c804bb450454 ] Commit 172b2386ed16 ("KVM: x86: fix missed hardware breakpoints", 2016-02-10) worked around a case where the debug registers are not loaded correctly on preemption and on the first entry to KVM_RUN. However, Xiao Guangrong pointed out that the root cause must be that KVM_DEBUGREG_BP_ENABLED is not being set correctly. This can indeed happen due to the lazy debug exit mechanism, which does not call kvm_update_dr7. Fix it by replacing the existing loop (more or less equivalent to kvm_update_dr0123) with calls to all the kvm_update_dr* functions. Cc: stable@vger.kernel.org # 4.1+ Fixes: 172b2386ed16a9143d9a456aae5ec87275c61489 Reviewed-by: Xiao Guangrong Signed-off-by: Paolo Bonzini Signed-off-by: Sasha Levin --- arch/x86/kvm/x86.c | 9 ++++----- 1 file changed, 4 insertions(+), 5 deletions(-) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 0dbf28a..42f1575 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -2968,7 +2968,6 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu) accumulate_steal_time(vcpu); kvm_make_request(KVM_REQ_STEAL_UPDATE, vcpu); - vcpu->arch.switch_db_regs |= KVM_DEBUGREG_RELOAD; } void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu) @@ -6372,12 +6371,12 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu) * KVM_DEBUGREG_WONT_EXIT again. */ if (unlikely(vcpu->arch.switch_db_regs & KVM_DEBUGREG_WONT_EXIT)) { - int i; - WARN_ON(vcpu->guest_debug & KVM_GUESTDBG_USE_HW_BP); kvm_x86_ops->sync_dirty_debug_regs(vcpu); - for (i = 0; i < KVM_NR_DB_REGS; i++) - vcpu->arch.eff_db[i] = vcpu->arch.db[i]; + kvm_update_dr0123(vcpu); + kvm_update_dr6(vcpu); + kvm_update_dr7(vcpu); + vcpu->arch.switch_db_regs &= ~KVM_DEBUGREG_RELOAD; } /* -- 2.7.4