This is a note to let you know that I've just added the patch titled
KVM: x86: fix root cause for missed hardware breakpoints
to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
kvm-x86-fix-root-cause-for-missed-hardware-breakpoints.patch
and it can be found in the queue-4.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 70e4da7a8ff62f2775337b705f45c804bb450454 Mon Sep 17 00:00:00 2001
From: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Date: Fri, 26 Feb 2016 12:28:40 +0100
Subject: KVM: x86: fix root cause for missed hardware breakpoints
From: Paolo Bonzini <pbonzini@xxxxxxxxxx>
commit 70e4da7a8ff62f2775337b705f45c804bb450454 upstream.
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.
Fixes: 172b2386ed16a9143d9a456aae5ec87275c61489
Reviewed-by: Xiao Guangrong <guangrong.xiao@xxxxxxxxxxxxxxx>
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/x86/kvm/x86.c | 9 ++++-----
1 file changed, 4 insertions(+), 5 deletions(-)
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -2736,7 +2736,6 @@ void kvm_arch_vcpu_load(struct kvm_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)
@@ -6545,12 +6544,12 @@ static int vcpu_enter_guest(struct kvm_v
* 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;
}
/*
Patches currently in stable-queue which might be from pbonzini@xxxxxxxxxx are
queue-4.4/kvm-x86-update-tsc-multiplier-on-change.patch
queue-4.4/kvm-x86-fix-root-cause-for-missed-hardware-breakpoints.patch
queue-4.4/mips-kvm-fix-ioctl-error-handling.patch
--
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