From: Sean Christopherson <seanjc@google.com>
To: Like Xu <like.xu@linux.intel.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>,
Vitaly Kuznetsov <vkuznets@redhat.com>,
Wanpeng Li <wanpengli@tencent.com>,
Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
kvm@vger.kernel.org, x86@kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/2] KVM: vmx/pmu: Clear DEBUGCTLMSR_LBR bit on the debug breakpoint event
Date: Tue, 23 Feb 2021 08:38:29 -0800 [thread overview]
Message-ID: <YDUvhTyFVwwZHnEj@google.com> (raw)
In-Reply-To: <20210223013958.1280444-2-like.xu@linux.intel.com>
On Tue, Feb 23, 2021, Like Xu wrote:
> When the processor that support model-specific LBR generates a debug
> breakpoint event, it automatically clears the LBR flag. This action
> does not clear previously stored LBR stack MSRs. (Intel SDM 17.4.2)
>
> Signed-off-by: Like Xu <like.xu@linux.intel.com>
> ---
> arch/x86/kvm/vmx/vmx.c | 5 +++++
> 1 file changed, 5 insertions(+)
>
> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> index e0a3a9be654b..4951b535eb7f 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -4795,6 +4795,7 @@ static int handle_exception_nmi(struct kvm_vcpu *vcpu)
> u32 intr_info, ex_no, error_code;
> unsigned long cr2, rip, dr6;
> u32 vect_info;
> + u64 lbr_ctl;
>
> vect_info = vmx->idt_vectoring_info;
> intr_info = vmx_get_intr_info(vcpu);
> @@ -4886,6 +4887,10 @@ static int handle_exception_nmi(struct kvm_vcpu *vcpu)
> rip = kvm_rip_read(vcpu);
> kvm_run->debug.arch.pc = vmcs_readl(GUEST_CS_BASE) + rip;
> kvm_run->debug.arch.exception = ex_no;
> + /* On the debug breakpoint event, the LBREn bit is cleared. */
Except this code is in BP_VECTOR, not DB_VECTOR as it should be.
When the processor generates a debug exception (#DB), it automatically clears
the LBR flag before executing the exception handler. This action does not
clear previously stored LBR stack MSRs.
> + lbr_ctl = vmcs_read64(GUEST_IA32_DEBUGCTL);
> + if (lbr_ctl & DEBUGCTLMSR_LBR)
> + vmcs_write64(GUEST_IA32_DEBUGCTL, lbr_ctl & ~DEBUGCTLMSR_LBR);
> break;
> case AC_VECTOR:
> if (guest_inject_ac(vcpu)) {
> --
> 2.29.2
>
next prev parent reply other threads:[~2021-02-23 16:39 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-23 1:39 [PATCH 1/2] KVM: vmx/pmu: Fix dummy check if lbr_desc->event is created Like Xu
2021-02-23 1:39 ` [PATCH 2/2] KVM: vmx/pmu: Clear DEBUGCTLMSR_LBR bit on the debug breakpoint event Like Xu
2021-02-23 16:38 ` Sean Christopherson [this message]
2021-02-23 17:06 ` Paolo Bonzini
2021-02-23 17:06 ` [PATCH 1/2] KVM: vmx/pmu: Fix dummy check if lbr_desc->event is created Paolo Bonzini
2021-02-23 17:15 ` Sean Christopherson
2021-02-23 17:19 ` Paolo Bonzini
2021-02-24 2:29 ` Xu, Like
2021-02-26 22:46 ` Sean Christopherson
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=YDUvhTyFVwwZHnEj@google.com \
--to=seanjc@google.com \
--cc=jmattson@google.com \
--cc=joro@8bytes.org \
--cc=kvm@vger.kernel.org \
--cc=like.xu@linux.intel.com \
--cc=linux-kernel@vger.kernel.org \
--cc=pbonzini@redhat.com \
--cc=vkuznets@redhat.com \
--cc=wanpengli@tencent.com \
--cc=x86@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox