From: Paolo Bonzini <pbonzini@redhat.com>
To: Lai Jiangshan <laijs@linux.alibaba.com>,
Lai Jiangshan <jiangshanlai@gmail.com>,
linux-kernel@vger.kernel.org
Cc: Sean Christopherson <seanjc@google.com>,
Vitaly Kuznetsov <vkuznets@redhat.com>,
Wanpeng Li <wanpengli@tencent.com>,
Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
kvm@vger.kernel.org
Subject: Re: [PATCH] KVM: X86: Also reload the debug registers before kvm_x86->run() when the host is using them
Date: Fri, 9 Jul 2021 11:49:00 +0200 [thread overview]
Message-ID: <397a448e-ffa7-3bea-af86-e92fbb273a07@redhat.com> (raw)
In-Reply-To: <c79d0167-7034-ebe2-97b7-58354d81323d@linux.alibaba.com>
On 09/07/21 05:09, Lai Jiangshan wrote:
> I just noticed that emulation.c fails to emulate with DBn.
> Is there any problem around it?
Just what you said, it's not easy and the needs are limited. I
implemented kvm_vcpu_check_breakpoint because I was interested in using
hardware breakpoints from gdb, even with unrestricted_guest=0 and
invalid guest state, but that's it.
Paolo
> For code breakpoint, if the instruction didn't cause vm-exit,
> (for example, the 2nd instruction when kvm emulates instructions
> back to back) emulation.c fails to emulate with DBn.
>
> For code breakpoint, if the instruction just caused vm-exit.
> It is difficult to analyze this case due to the complex priorities
> between vectored events and fault-like vm-exit.
> Anyway, if it is an instruction that vm-exit has priority over #DB,
> emulation.c fails to emulate with DBn.
>
> For data breakpoint, a #DB must be delivered to guest or to VMM (when
> guest-debug) after the instruction. But emulation.c doesn't do so.
>
> And the existence of both of effective DBn (guest debug) and guest DBn
> complicates the problem when we try to emulate them.
next prev parent reply other threads:[~2021-07-09 9:49 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-28 17:26 [PATCH] KVM: X86: Also reload the debug registers before kvm_x86->run() when the host is using them Lai Jiangshan
2021-07-08 16:48 ` Paolo Bonzini
2021-07-09 3:09 ` Lai Jiangshan
2021-07-09 9:49 ` Paolo Bonzini [this message]
2021-07-09 10:05 ` Lai Jiangshan
2021-07-09 15:52 ` Paolo Bonzini
2021-07-09 16:35 ` Jim Mattson
2021-07-09 16:58 ` Paolo Bonzini
2021-07-09 17:01 ` Jim Mattson
2021-07-09 16:49 ` Sean Christopherson
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