From: Maxim Levitsky <mlevitsk@redhat.com>
To: Paolo Bonzini <pbonzini@redhat.com>,
Sean Christopherson <seanjc@google.com>
Cc: kvm@vger.kernel.org, Thomas Gleixner <tglx@linutronix.de>,
x86@kernel.org, Borislav Petkov <bp@alien8.de>,
Ingo Molnar <mingo@redhat.com>,
Vitaly Kuznetsov <vkuznets@redhat.com>,
Joerg Roedel <joro@8bytes.org>,
Wanpeng Li <wanpengli@tencent.com>,
"H. Peter Anvin" <hpa@zytor.com>,
linux-kernel@vger.kernel.org, Jim Mattson <jmattson@google.com>
Subject: Re: [PATCH v2 2/3] KVM: nVMX: add kvm_nested_vmlaunch_resume tracepoint
Date: Thu, 21 Jan 2021 18:58:03 +0200 [thread overview]
Message-ID: <7f9f2fa0a6246573afab18822829120389352ad3.camel@redhat.com> (raw)
In-Reply-To: <18c386f2-a588-6324-fcde-d13b66f66d4f@redhat.com>
On Fri, 2021-01-15 at 14:48 +0100, Paolo Bonzini wrote:
> On 15/01/21 01:14, Sean Christopherson wrote:
> > > + trace_kvm_nested_vmlaunch_resume(kvm_rip_read(vcpu),
> > Hmm, won't this RIP be wrong for the migration case? I.e. it'll be L2, not L1
> > as is the case for the "true" nested VM-Enter path.
Actually in this case, the initial RIP of 0x000000000000fff0 will be printed
which isn't that bad.
A tracepoint in nested state load function would be very nice to add
to mark this explicitly. I'll do this later.
>
> It will be the previous RIP---might as well be 0xfffffff0 depending on
> what userspace does. I don't think you can do much better than that,
> using vmcs12->host_rip would be confusing in the SMM case.
>
> > > + vmx->nested.current_vmptr,
> > > + vmcs12->guest_rip,
> > > + vmcs12->vm_entry_intr_info_field);
> > The placement is a bit funky. I assume you put it here so that calls from
> > vmx_set_nested_state() also get traced. But, that also means
> > vmx_pre_leave_smm() will get traced, and it also creates some weirdness where
> > some nested VM-Enters that VM-Fail will get traced, but others will not.
> >
> > Tracing vmx_pre_leave_smm() isn't necessarily bad, but it could be confusing,
> > especially if the debugger looks up the RIP and sees RSM. Ditto for the
> > migration case.
>
> Actually tracing vmx_pre_leave_smm() is good, and pointing to RSM makes
> sense so I'm not worried about that.
>
> Paolo
>
I agree with that and indeed this was my intention.
In fact I will change the svm's tracepoint to behave the same way
in the next patch series (I'll move it to enter_svm_guest_mode).
(When I wrote this patch I somehow thought that this is what SVM already does).
Best regards,
Maxim Levitsky
next prev parent reply other threads:[~2021-01-21 17:00 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-14 20:54 [PATCH v2 0/3] VMX: more nested fixes Maxim Levitsky
2021-01-14 20:54 ` [PATCH v2 1/3] KVM: nVMX: Always call sync_vmcs02_to_vmcs12_rare on migration Maxim Levitsky
2021-01-14 23:58 ` Sean Christopherson
2021-01-21 14:59 ` Paolo Bonzini
2021-01-14 20:54 ` [PATCH v2 2/3] KVM: nVMX: add kvm_nested_vmlaunch_resume tracepoint Maxim Levitsky
2021-01-15 0:14 ` Sean Christopherson
2021-01-15 13:48 ` Paolo Bonzini
2021-01-15 16:30 ` Sean Christopherson
2021-01-21 17:00 ` Maxim Levitsky
2021-01-21 16:58 ` Maxim Levitsky [this message]
2021-01-21 17:02 ` Maxim Levitsky
2021-01-14 20:54 ` [PATCH v2 3/3] KVM: VMX: read idt_vectoring_info a bit earlier Maxim Levitsky
2021-01-15 0:29 ` Sean Christopherson
2021-01-21 17:04 ` Maxim Levitsky
2021-01-21 15:00 ` [PATCH v2 0/3] VMX: more nested fixes Paolo Bonzini
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