From: Sasha Levin <levinsasha928@gmail.com>
To: Jan Kiszka <jan.kiszka@siemens.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>,
Avi Kivity <avi@redhat.com>,
Marcelo Tosatti <mtosatti@redhat.com>,
"kvm@vger.kernel.org" <kvm@vger.kernel.org>,
Alex Williamson <alex.williamson@redhat.com>
Subject: Re: [PATCH 0/4 v9] MSI-X MMIO support for KVM
Date: Tue, 06 Sep 2011 12:00:00 +0300 [thread overview]
Message-ID: <1315299600.2615.6.camel@sasha> (raw)
In-Reply-To: <4E65DEA4.8070203@siemens.com>
On Tue, 2011-09-06 at 10:49 +0200, Jan Kiszka wrote:
> On 2011-09-06 10:46, Sasha Levin wrote:
> > On Tue, 2011-09-06 at 10:36 +0200, Jan Kiszka wrote:
> >> On 2011-09-06 10:12, Michael S. Tsirkin wrote:
> >>> On Tue, Sep 06, 2011 at 10:52:41AM +0300, Avi Kivity wrote:
> >>>>>
> >>>>> BTW, the same is also true for that optional per-vector masking of
> >>>>> legacy MSI. Are there devices in the field that actually support this? I
> >>>>> haven't found one so far and tend to consider this feature not worth
> >>>>> implementing.
> >>>>
> >>>> Don't know. I don't like implementing features on the basis of bug
> >>>> reports, though. On the other hand we can't really test it without
> >>>> a real device.
> >>>
> >>> Linux will use this capability if present. So
> >>> we could add support for an emulated device (e.g. e1000),
> >>> then test with nested virt once iommu emulation lands :)
> >>
> >> Yeah, would be kind of cool. Still, I would feel better having it tested
> >> against a real silicon as well. Also to prove that there is a real need.
> >>
> >> So, in case someone stumbles for such a device (bit 8 set in MSI control
> >> word), please let us know!
> >
> > Doesn't any device that supports MSI-X supports per-vector masking?
> >
> >>From the spec:
> >
> > "MSI and MSI-X each support per-vector masking. Per-vector masking is an
> > optional extension to MSI, and a standard feature with MSI-X"
>
> Right, but the cap flag still has to be set.
>
Are you sure? Take a look at the table in section 6.8.2.3 in the spec
(pci v3). Unlike the message control for MSI, this table doesn't mention
anything about bit 8 or the per-vector masking capability for MSI-X, it
just assumes it's there.
> Do you have any MSI-X device in reach?
Don't think so, but I think it would be much easier to find a MSI-X
device rather than a MSI with per-vector capability.
--
Sasha.
next prev parent reply other threads:[~2011-09-06 9:00 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-02-18 8:53 [PATCH 0/4 v9] MSI-X MMIO support for KVM Sheng Yang
2011-02-18 8:53 ` [PATCH 1/4] KVM: Move struct kvm_io_device to kvm_host.h Sheng Yang
2011-02-18 8:53 ` [PATCH 2/4] KVM: Add kvm_io_ext_data to IO handler Sheng Yang
2011-02-18 8:53 ` [PATCH 3/4] KVM: Emulate MSI-X table in kernel Sheng Yang
2011-02-18 8:53 ` [PATCH 4/4] KVM: Add documents for MSI-X MMIO API Sheng Yang
2011-02-22 18:08 ` [PATCH 0/4 v9] MSI-X MMIO support for KVM Marcelo Tosatti
2011-09-01 11:27 ` Jan Kiszka
2011-09-06 7:52 ` Avi Kivity
2011-09-06 8:12 ` Michael S. Tsirkin
2011-09-06 8:36 ` Jan Kiszka
2011-09-06 8:46 ` Sasha Levin
2011-09-06 8:49 ` Jan Kiszka
2011-09-06 9:00 ` Sasha Levin [this message]
2011-09-06 9:05 ` Jan Kiszka
2011-09-06 9:16 ` Sasha Levin
2011-09-06 9:30 ` Michael S. Tsirkin
2011-09-06 8:36 ` Jan Kiszka
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=1315299600.2615.6.camel@sasha \
--to=levinsasha928@gmail.com \
--cc=alex.williamson@redhat.com \
--cc=avi@redhat.com \
--cc=jan.kiszka@siemens.com \
--cc=kvm@vger.kernel.org \
--cc=mst@redhat.com \
--cc=mtosatti@redhat.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).