From: Paolo Bonzini <pbonzini@redhat.com>
To: Lai Jiangshan <jiangshanlai+lkml@gmail.com>,
Sean Christopherson <sean.j.christopherson@intel.com>
Cc: Vitaly Kuznetsov <vkuznets@redhat.com>,
Wanpeng Li <wanpengli@tencent.com>,
Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
kvm@vger.kernel.org, LKML <linux-kernel@vger.kernel.org>,
Josh Poimboeuf <jpoimboe@redhat.com>,
Uros Bizjak <ubizjak@gmail.com>, Andi Kleen <ak@linux.intel.com>,
Andy Lutomirski <luto@kernel.org>,
Steven Rostedt <rostedt@goodmis.org>
Subject: Re: [PATCH v2 2/2] KVM: VMX: Invoke NMI handler via indirect call instead of INTn
Date: Mon, 26 Apr 2021 12:40:28 +0200 [thread overview]
Message-ID: <bb2c2d93-8046-017a-5711-c61c8f1a4c09@redhat.com> (raw)
In-Reply-To: <CAJhGHyBOLUeqnwx2X=WToE2oY8Zkqj_y4KZ0hoq-goe+UWcR9g@mail.gmail.com>
On 26/04/21 11:33, Lai Jiangshan wrote:
> When handle_interrupt_nmi_irqoff() is called, we may lose the
> CPU-hidden-NMI-masked state due to IRET of #DB, #BP or other traps
> between VMEXIT and handle_interrupt_nmi_irqoff().
>
> But the NMI handler in the Linux kernel*expects* the CPU-hidden-NMI-masked
> state is still set in the CPU for no nested NMI intruding into the beginning
> of the handler.
>
> The original code "int $2" can provide the needed CPU-hidden-NMI-masked
> when entering #NMI, but I doubt it about this change.
How would "int $2" block NMIs? The hidden effect of this change (and I
should have reviewed better the effect on the NMI entry code) is that
the call will not use the IST anymore.
However, I'm not sure which of the two situations is better: entering
the NMI handler on the IST without setting the hidden NMI-blocked flag
could be a recipe for bad things as well.
Paolo
next prev parent reply other threads:[~2021-04-26 10:40 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-15 19:15 [PATCH v2 0/2] KVM: VMX: Clean up IRQ/NMI handling Sean Christopherson
2020-09-15 19:15 ` [PATCH v2 1/2] KVM: VMX: Move IRQ invocation to assembly subroutine Sean Christopherson
2020-09-15 19:27 ` Josh Poimboeuf
2020-09-15 19:38 ` Uros Bizjak
2020-09-15 19:15 ` [PATCH v2 2/2] KVM: VMX: Invoke NMI handler via indirect call instead of INTn Sean Christopherson
2021-04-26 9:33 ` Lai Jiangshan
2021-04-26 10:40 ` Paolo Bonzini [this message]
2021-04-26 11:44 ` Maxim Levitsky
2021-04-26 13:59 ` Steven Rostedt
2021-04-26 14:51 ` Andi Kleen
2021-04-26 15:09 ` Andy Lutomirski
2021-04-27 0:54 ` Lai Jiangshan
2021-04-27 1:00 ` Steven Rostedt
2021-04-27 7:05 ` Paolo Bonzini
2021-04-30 2:56 ` Lai Jiangshan
2020-09-22 13:38 ` [PATCH v2 0/2] KVM: VMX: Clean up IRQ/NMI handling Paolo Bonzini
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=bb2c2d93-8046-017a-5711-c61c8f1a4c09@redhat.com \
--to=pbonzini@redhat.com \
--cc=ak@linux.intel.com \
--cc=jiangshanlai+lkml@gmail.com \
--cc=jmattson@google.com \
--cc=joro@8bytes.org \
--cc=jpoimboe@redhat.com \
--cc=kvm@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=luto@kernel.org \
--cc=rostedt@goodmis.org \
--cc=sean.j.christopherson@intel.com \
--cc=ubizjak@gmail.com \
--cc=vkuznets@redhat.com \
--cc=wanpengli@tencent.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).