From: Vitaly Kuznetsov <vkuznets@redhat.com>
To: Paolo Bonzini <pbonzini@redhat.com>, qemu-devel@nongnu.org
Cc: Richard Henderson <rth@twiddle.net>,
Eduardo Habkost <ehabkost@redhat.com>,
Marcelo Tosatti <mtosatti@redhat.com>,
Roman Kagan <rkagan@virtuozzo.com>
Subject: Re: [Qemu-devel] [PATCH] i386/kvm: expose HV_CPUID_ENLIGHTMENT_INFO.EAX and HV_CPUID_NESTED_FEATURES.EAX as feature words
Date: Thu, 29 Nov 2018 12:51:55 +0100 [thread overview]
Message-ID: <878t1chzj8.fsf@vitty.brq.redhat.com> (raw)
In-Reply-To: <c30c335e-ca21-1179-670b-d4506ce14571@redhat.com>
Paolo Bonzini <pbonzini@redhat.com> writes:
> On 26/11/18 14:59, Vitaly Kuznetsov wrote:
>> It was found that QMP users of QEMU (e.g. libvirt) may need
>> HV_CPUID_ENLIGHTMENT_INFO.EAX/HV_CPUID_NESTED_FEATURES.EAX information. In
>> particular, 'hv_tlbflush' and 'hv_evmcs' enlightenments are only exposed in
>> HV_CPUID_ENLIGHTMENT_INFO.EAX.
>>
>> HV_CPUID_NESTED_FEATURES.EAX is exposed for two reasons: convenience
>> (we don't need to export it from hyperv_handle_properties() and as
>> future-proof for Enlightened MSR-Bitmap, PV EPT invalidation and
>> direct virtual flush features.
>>
>> Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
>
> Can you add a comment to feature_word_info, explaining why the
> feat_names are not set?
I had to do some code archeology to make sure I understand, I think it
goes back to
http://lists.gnu.org/archive/html/qemu-devel/2016-06/msg06579.html
So the comment (probably added before FEAT_HYPERV_EAX definition) would
be
".feat_names are commented out for Hyper-V enlightenments because we
don't want to have two different ways for enabling them on QEMU command
line. Some features (e.g. "hyperv_time", "hyperv_vapic", ...) require
enabling several feature bits simultaneously, exposing these bits
individually may just confuse guests."
Would do?
--
Vitaly
next prev parent reply other threads:[~2018-11-29 12:00 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-26 13:59 [Qemu-devel] [PATCH] i386/kvm: expose HV_CPUID_ENLIGHTMENT_INFO.EAX and HV_CPUID_NESTED_FEATURES.EAX as feature words Vitaly Kuznetsov
2018-11-27 13:10 ` Roman Kagan
2018-11-29 10:20 ` Paolo Bonzini
2018-11-29 11:51 ` Vitaly Kuznetsov [this message]
2018-11-30 18:36 ` Eduardo Habkost
2018-12-03 14:17 ` Vitaly Kuznetsov
2018-12-04 18:08 ` Eduardo Habkost
2018-12-05 13:12 ` Vitaly Kuznetsov
2018-12-19 17:25 ` Vitaly Kuznetsov
2018-12-20 12:05 ` Eduardo Habkost
2018-12-21 14:14 ` Vitaly Kuznetsov
2019-01-14 10:54 ` Vitaly Kuznetsov
2019-01-14 14:32 ` Eduardo Habkost
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=878t1chzj8.fsf@vitty.brq.redhat.com \
--to=vkuznets@redhat.com \
--cc=ehabkost@redhat.com \
--cc=mtosatti@redhat.com \
--cc=pbonzini@redhat.com \
--cc=qemu-devel@nongnu.org \
--cc=rkagan@virtuozzo.com \
--cc=rth@twiddle.net \
/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 an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.