From: Sean Christopherson <sean.j.christopherson@intel.com>
To: Vitaly Kuznetsov <vkuznets@redhat.com>
Cc: Xiaoyao Li <xiaoyao.li@intel.com>,
Chenyi Qiang <chenyi.qiang@intel.com>,
kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
Paolo Bonzini <pbonzini@redhat.com>,
Wanpeng Li <wanpengli@tencent.com>,
Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>
Subject: Re: [RFC 2/2] KVM: VMX: Enable bus lock VM exit
Date: Wed, 22 Jul 2020 18:21:14 -0700 [thread overview]
Message-ID: <20200723012114.GP9114@linux.intel.com> (raw)
In-Reply-To: <87zh8j9to2.fsf@vitty.brq.redhat.com>
On Wed, Jul 01, 2020 at 04:49:49PM +0200, Vitaly Kuznetsov wrote:
> Xiaoyao Li <xiaoyao.li@intel.com> writes:
> > So you want an exit to userspace for every bus lock and leave it all to
> > userspace. Yes, it's doable.
>
> In some cases we may not even want to have a VM exit: think
> e.g. real-time/partitioning case when even in case of bus lock we may
> not want to add additional latency just to count such events.
Hmm, I suspect this isn't all that useful for real-time cases because they'd
probably want to prevent the split lock in the first place, e.g. would prefer
to use the #AC variant in fatal mode. Of course, the availability of split
lock #AC is a whole other can of worms.
But anyways, I 100% agree that this needs either an off-by-default module
param or an opt-in per-VM capability.
> I'd suggest we make the new capability tri-state:
> - disabled (no vmexit, default)
> - stats only (what this patch does)
> - userspace exit
> But maybe this is an overkill, I'd like to hear what others think.
Userspace exit would also be interesting for debug. Another throttling
option would be schedule() or cond_reched(), though that's probably getting
into overkill territory.
next prev parent reply other threads:[~2020-07-23 1:21 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-28 8:53 [RFC 0/2] Add support for bus lock VM exit Chenyi Qiang
2020-06-28 8:53 ` [RFC 1/2] KVM: VMX: Convert vcpu_vmx.exit_reason to a union Chenyi Qiang
2020-06-28 8:53 ` [RFC 2/2] KVM: VMX: Enable bus lock VM exit Chenyi Qiang
2020-07-01 9:04 ` Vitaly Kuznetsov
2020-07-01 9:32 ` Xiaoyao Li
2020-07-01 12:44 ` Vitaly Kuznetsov
2020-07-01 14:12 ` Xiaoyao Li
2020-07-01 14:49 ` Vitaly Kuznetsov
2020-07-02 9:15 ` Xiaoyao Li
2020-07-23 1:21 ` Sean Christopherson [this message]
2020-07-27 4:38 ` Xiaoyao Li
2020-07-28 16:25 ` Sean Christopherson
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=20200723012114.GP9114@linux.intel.com \
--to=sean.j.christopherson@intel.com \
--cc=chenyi.qiang@intel.com \
--cc=jmattson@google.com \
--cc=joro@8bytes.org \
--cc=kvm@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=pbonzini@redhat.com \
--cc=vkuznets@redhat.com \
--cc=wanpengli@tencent.com \
--cc=xiaoyao.li@intel.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).