From: Paolo Bonzini <pbonzini@redhat.com>
To: Andy Lutomirski <luto@kernel.org>,
Sean Christopherson <sean.j.christopherson@intel.com>
Cc: Tao Xu <tao3.xu@intel.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>,
"H. Peter Anvin" <hpa@zytor.com>, X86 ML <x86@kernel.org>,
kvm list <kvm@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
Xiaoyao Li <xiaoyao.li@intel.com>
Subject: Re: [PATCH] KVM: VMX: Enable Notify VM exit
Date: Mon, 2 Nov 2020 19:25:37 +0100 [thread overview]
Message-ID: <8e41101c-6278-3773-8754-ffe0763eaeea@redhat.com> (raw)
In-Reply-To: <CALCETrV0ZsTcQKVCPPSKHnuVgERMC0x86G5y_6E5Rhf=h5JzsA@mail.gmail.com>
On 02/11/20 19:01, Andy Lutomirski wrote:
> What's the point? Surely the kernel should reliably mitigate the
> flaw, and the kernel should decide how to do so.
There is some slowdown in trapping #DB and #AC unconditionally. Though
for these two cases nobody should care so I agree with keeping the code
simple and keeping the workaround.
Also, why would this trigger after more than a few hundred cycles,
something like the length of the longest microcode loop? HZ*10 seems
like a very generous estimate already.
Paolo
>>> I also think you should print a loud warning
>> I'm not so sure on this one, e.g. userspace could just spin up a new instance
>> if its malicious guest and spam the kernel log.
> pr_warn_once()? If this triggers, it's a *bug*, right? Kernel or CPU.
>
next prev parent reply other threads:[~2020-11-02 18:25 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-02 6:14 Tao Xu
2020-11-02 16:43 ` Andy Lutomirski
2020-11-02 17:31 ` Sean Christopherson
2020-11-02 18:01 ` Andy Lutomirski
2020-11-02 18:25 ` Paolo Bonzini [this message]
2020-11-03 6:39 ` Xiaoyao Li
2020-11-02 18:33 ` Sean Christopherson
2021-05-17 7:20 ` Xiaoyao Li
2021-05-17 8:55 ` Xiaoyao Li
2020-11-03 5:35 ` Tao Xu
2020-11-03 6:08 ` Tao Xu
2020-11-03 7:29 ` Xiaoyao Li
2020-11-02 17:32 ` Sean Christopherson
2020-11-03 5:36 ` Tao Xu
2020-11-02 22:53 ` Jim Mattson
2020-11-03 6:12 ` Tao Xu
2020-11-03 6:24 ` Xiaoyao Li
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