From: Andrew Cooper <Andrew.Cooper3@citrix.com>
To: Sean Christopherson <seanjc@google.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
"x86@kernel.org" <x86@kernel.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"Guilherme G . Piccoli" <gpiccoli@igalia.com>,
Vitaly Kuznetsov <vkuznets@redhat.com>,
Paolo Bonzini <pbonzini@redhat.com>,
Tom Lendacky <thomas.lendacky@amd.com>,
Andrew Cooper <Andrew.Cooper3@citrix.com>
Subject: Re: [PATCH v3 0/3] x86/crash: Fix double NMI shootdown bug
Date: Tue, 15 Nov 2022 00:32:24 +0000 [thread overview]
Message-ID: <5b8787b8-16e9-13dc-7fca-0dc441d673f9@citrix.com> (raw)
In-Reply-To: <20221114233441.3895891-1-seanjc@google.com>
On 14/11/2022 23:34, Sean Christopherson wrote:
> Tom,
>
> I Cc'd you this time around because the APM doesn't explicitly state that
> GIF is set when EFER.SVME is disabled. KVM's nSVM emulation does set GIF
> in this case, but it's not clear whether or not KVM is making up behavior.
> If clearing EFER.SVME doesn't set GIF, then patch 1 needs to be modified
> to try STGI before clearing EFER.SVME, e.g. if a crash is initiated from
> KVM between CLGI and STGI. Responding CPUs are "safe" because GIF=0 also
> blocks NMIs, but the initiating CPU might leave GIF=0 when jumping into
> the new kernel.
GIF exists independently of EFER.SVME.
It is also gets set by the SKINIT instruction, which is why there is an
asymmetry on the #UD conditions of STGI and CLGI.
STGI is also intended to be used by the DLME once critical
initialisation is done, hence why it's dependent on EFER.SVME || SKINIT.
~Andrew
next prev parent reply other threads:[~2022-11-15 0:32 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-11-14 23:34 Sean Christopherson
2022-11-14 23:34 ` [PATCH v3 1/3] x86/crash: Disable virt in core NMI crash handler to avoid double shootdown Sean Christopherson
2022-11-14 23:34 ` [PATCH v3 2/3] x86/reboot: Disable virtualization in an emergency if SVM is supported Sean Christopherson
2022-11-14 23:34 ` [PATCH v3 3/3] x86/virt: Fold __cpu_emergency_vmxoff() into its sole caller Sean Christopherson
2022-11-15 0:32 ` Andrew Cooper [this message]
2022-11-15 16:56 ` [PATCH v3 0/3] x86/crash: Fix double NMI shootdown bug Sean Christopherson
2022-11-15 18:34 ` Tom Lendacky
2022-11-15 19:58 ` Andrew Cooper
2022-11-15 15:33 ` Guilherme G. Piccoli
2022-11-15 19:36 ` Sean Christopherson
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