From: Lai Jiangshan <jiangshanlai@gmail.com>
To: Andy Lutomirski <luto@amacapital.net>
Cc: Sean Christopherson <seanjc@google.com>,
Paolo Bonzini <pbonzini@redhat.com>,
Maxim Levitsky <mlevitsk@redhat.com>,
Thomas Gleixner <tglx@linutronix.de>,
LKML <linux-kernel@vger.kernel.org>,
Lai Jiangshan <laijs@linux.alibaba.com>,
Steven Rostedt <rostedt@goodmis.org>,
Andi Kleen <ak@linux.intel.com>,
Andy Lutomirski <luto@kernel.org>,
Vitaly Kuznetsov <vkuznets@redhat.com>,
Wanpeng Li <wanpengli@tencent.com>,
Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
Josh Poimboeuf <jpoimboe@redhat.com>,
Uros Bizjak <ubizjak@gmail.com>, Ingo Molnar <mingo@redhat.com>,
Borislav Petkov <bp@alien8.de>, X86 ML <x86@kernel.org>,
"H. Peter Anvin" <hpa@zytor.com>,
Peter Zijlstra <peterz@infradead.org>,
Alexandre Chartre <alexandre.chartre@oracle.com>,
Juergen Gross <JGross@suse.com>, Joerg Roedel <jroedel@suse.de>,
Jian Cai <caij2003@gmail.com>
Subject: Re: [PATCH] KVM/VMX: Invoke NMI non-IST entry instead of IST entry
Date: Wed, 5 May 2021 09:07:50 +0800 [thread overview]
Message-ID: <CAJhGHyDsTVyDX9fkYAyVkVQFWqkyTAVCY4enJqdG4bzOuOSn+w@mail.gmail.com> (raw)
In-Reply-To: <38B9D60F-F24F-4910-B2DF-2A57F1060452@amacapital.net>
On Wed, May 5, 2021 at 5:23 AM Andy Lutomirski <luto@amacapital.net> wrote:
>
>
> > On May 4, 2021, at 2:21 PM, Sean Christopherson <seanjc@google.com> wrote:
> >
> > On Tue, May 04, 2021, Paolo Bonzini wrote:
> >>> On 04/05/21 23:05, Maxim Levitsky wrote:
> >>> Does this mean that we still rely on hardware NMI masking to be activated?
> >>
> >> No, the NMI code already handles reentrancy at both the assembly and C
> >> levels.
> >>
> >>> Or in other words, that is we still can't have an IRET between VM exit and
> >>> the entry to the NMI handler?
> >>
> >> No, because NMIs are not masked on VM exit. This in fact makes things
> >> potentially messy; unlike with AMD's CLGI/STGI, only MSRs and other things
> >> that Intel thought can be restored atomically with the VM exit.
> >
> > FWIW, NMIs are masked if the VM-Exit was due to an NMI.
>
> Then this whole change is busted, since nothing will unmask NMIs. Revert it?
There is some instructable code between VMEXIT and
handle_exception_nmi_irqoff().
The possible #DB #BP can happen in this gap and the IRET
of the handler of #DB #BP will unmask NMI.
Another way to fix is to change the VMX code to call the NMI handler
immediately after VMEXIT before leaving "nostr" section.
Reverting it can't fix the problem.
next prev parent reply other threads:[~2021-05-05 1:08 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-26 23:09 [PATCH 0/4] x86: Don't invoke asm_exc_nmi() on the kernel stack Lai Jiangshan
2021-04-26 23:09 ` [PATCH 1/4] x86/xen/entry: Rename xenpv_exc_nmi to noist_exc_nmi Lai Jiangshan
2021-04-28 21:27 ` Steven Rostedt
2021-04-30 7:15 ` Paolo Bonzini
2021-04-30 12:05 ` Steven Rostedt
2021-05-03 19:05 ` Thomas Gleixner
2021-05-03 19:41 ` Thomas Gleixner
2021-05-10 7:59 ` Juergen Gross
2021-04-26 23:09 ` [PATCH 2/4] x86/entry: Use asm_noist_exc_nmi() for NMI in early booting stage Lai Jiangshan
2021-04-28 21:30 ` Steven Rostedt
2021-05-03 20:13 ` Thomas Gleixner
2021-05-03 20:24 ` Thomas Gleixner
2021-05-03 21:45 ` Thomas Gleixner
2021-05-04 12:43 ` Thomas Gleixner
2021-05-04 19:50 ` [PATCH] KVM/VMX: Invoke NMI non-IST entry instead of IST entry Thomas Gleixner
2021-05-04 21:05 ` Maxim Levitsky
2021-05-04 21:12 ` Paolo Bonzini
2021-05-04 21:21 ` Sean Christopherson
2021-05-04 21:23 ` Andy Lutomirski
2021-05-04 21:25 ` Paolo Bonzini
2021-05-04 21:51 ` Sean Christopherson
2021-05-04 21:56 ` Paolo Bonzini
2021-05-05 0:00 ` Thomas Gleixner
2021-05-05 15:44 ` Lai Jiangshan
2021-05-05 1:07 ` Lai Jiangshan [this message]
2021-05-05 1:11 ` Andy Lutomirski
2021-05-06 12:14 ` [tip: x86/urgent] " tip-bot2 for Lai Jiangshan
2021-04-26 23:09 ` [PATCH 3/4] " Lai Jiangshan
2021-04-30 2:46 ` Lai Jiangshan
2021-05-03 19:37 ` Thomas Gleixner
2021-05-03 20:02 ` Thomas Gleixner
2021-05-04 8:10 ` Paolo Bonzini
2021-04-26 23:09 ` [PATCH 4/4] KVM/VMX: Fold handle_interrupt_nmi_irqoff() into its solo caller Lai Jiangshan
2021-04-30 9:03 ` Thomas Gleixner
2021-04-30 9:06 ` Paolo Bonzini
2021-04-30 23:28 ` Thomas Gleixner
2021-04-30 7:14 ` [PATCH 0/4] x86: Don't invoke asm_exc_nmi() on the kernel stack Paolo Bonzini
2021-05-03 14:36 ` Thomas Gleixner
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