From: Xiaoyao Li <xiaoyao.li@intel.com>
To: Vitaly Kuznetsov <vkuznets@redhat.com>,
Chenyi Qiang <chenyi.qiang@intel.com>
Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
Paolo Bonzini <pbonzini@redhat.com>,
Sean Christopherson <sean.j.christopherson@intel.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, 1 Jul 2020 17:32:53 +0800 [thread overview]
Message-ID: <0159554d-82d5-b388-d289-a5375ca91323@intel.com> (raw)
In-Reply-To: <878sg3bo8b.fsf@vitty.brq.redhat.com>
On 7/1/2020 5:04 PM, Vitaly Kuznetsov wrote:
> Chenyi Qiang <chenyi.qiang@intel.com> writes:
[...]
>> static const int kvm_vmx_max_exit_handlers =
>> @@ -6830,6 +6838,13 @@ static fastpath_t vmx_vcpu_run(struct kvm_vcpu *vcpu)
>> if (unlikely(vmx->exit_reason.failed_vmentry))
>> return EXIT_FASTPATH_NONE;
>>
>> + /*
>> + * check the exit_reason to see if there is a bus lock
>> + * happened in guest.
>> + */
>> + if (vmx->exit_reason.bus_lock_detected)
>> + handle_bus_lock(vcpu);
>
> In case the ultimate goal is to have an exit to userspace on bus lock,
I don't think we will need an exit to userspace on bus lock. See below.
> the two ways to reach handle_bus_lock() are very different: in case
> we're handling EXIT_REASON_BUS_LOCK we can easily drop to userspace by
> returning 0 but what are we going to do in case of
> exit_reason.bus_lock_detected? The 'higher priority VM exit' may require
> exit to userspace too. So what's the plan? Maybe we can ignore the case
> when we're exiting to userspace for some other reason as this is slow
> already and force the exit otherwise?
> And should we actually introduce
> the KVM_EXIT_BUS_LOCK and a capability to enable it here?
>
Introducing KVM_EXIT_BUS_LOCK maybe help nothing. No matter
EXIT_REASON_BUS_LOCK or exit_reason.bus_lock_detected, the bus lock has
already happened. Exit to userspace cannot prevent bus lock, so what
userspace can do is recording and counting as what this patch does in
vcpu->stat.bus_locks.
next prev parent reply other threads:[~2020-07-01 9:33 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 [this message]
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
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=0159554d-82d5-b388-d289-a5375ca91323@intel.com \
--to=xiaoyao.li@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=sean.j.christopherson@intel.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).