From: Ingo Molnar <mingo@kernel.org>
To: Alexander Gordeev <agordeev@redhat.com>,
Bjorn Helgaas <bhelgaas@google.com>
Cc: linux-kernel@vger.kernel.org, x86@kernel.org,
linux-pci@vger.kernel.org,
Suresh Siddha <suresh.b.siddha@intel.com>,
Yinghai Lu <yinghai@kernel.org>, Joerg Roedel <joro@8bytes.org>,
Jan Beulich <JBeulich@suse.com>, Ingo Molnar <mingo@redhat.com>,
Bjorn Helgaas <bhelgaas@google.com>
Subject: Re: [PATCH v3 -tip x86/apic 1/2] PCI/MSI: Allocate as many multiple-MSIs as requested
Date: Tue, 28 May 2013 11:50:52 +0200 [thread overview]
Message-ID: <20130528095052.GA6764@gmail.com> (raw)
In-Reply-To: <8575dc590b819892f366852fe50835efaf579f4f.1368431413.git.agordeev@redhat.com>
* Alexander Gordeev <agordeev@redhat.com> wrote:
> When multiple MSIs are enabled with pci_enable_msi_block(), the
> requested number of interrupts 'nvec' is rounded up to the nearest
> power-of-two value. The result is then used for setting up the
> number of MSI messages in the PCI device and allocation of
> interrupt resources in the operating system (i.e. vector numbers).
> Thus, in cases when a device driver requests some number of MSIs
> and this number is not a power-of-two value, the extra operating
> system resources (allocated as the result of rounding) are wasted.
>
> This fix introduces 'msi_desc::nvec' field to address the above
> issue. When non-zero, it will report the actual number of MSIs the
> device will send, as requested by the device driver. This value
> should be used by architectures to properly set up and tear down
> associated interrupt resources.
>
> Note, although the existing 'msi_desc::multiple' field might seem
> redundant, in fact in does not. In general case the number of MSIs a
> PCI device is initialized with is not necessarily the closest power-
> of-two value of the number of MSIs the device will send. Thus, in
> theory it would not be always possible to derive the former from the
> latter and we need to keep them both, to stress this corner case.
> Besides, since 'msi_desc::multiple' is a bitfield, throwing it out
> would not save us any space.
>
> Signed-off-by: Alexander Gordeev <agordeev@redhat.com>
Would be nice to have an Acked-by from Bjorn for this patch.
Thanks,
Ingo
next prev parent reply other threads:[~2013-05-28 9:50 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-05-13 9:05 [PATCH v3 -tip x86/apic 0/2] PCI/MSI: Allocate as many multiple-MSIs as requested Alexander Gordeev
2013-05-13 9:05 ` [PATCH v3 -tip x86/apic 1/2] " Alexander Gordeev
2013-05-28 9:50 ` Ingo Molnar [this message]
2013-06-05 20:56 ` Sebastian Andrzej Siewior
2013-06-05 21:09 ` Bjorn Helgaas
2013-06-05 21:28 ` Sebastian Andrzej Siewior
2013-06-06 8:30 ` Alexander Gordeev
2013-06-06 19:51 ` Sebastian Andrzej Siewior
2013-05-13 9:06 ` [PATCH v3 -tip x86/apic 2/2] x86/MSI: Conserve interrupt resources when using multiple-MSIs Alexander Gordeev
2013-06-05 20:08 ` Sebastian Andrzej Siewior
2013-05-28 21:51 [PATCH v3 -tip x86/apic 1/2] PCI/MSI: Allocate as many multiple-MSIs as requested Bjorn Helgaas
2013-05-29 8:36 ` Alexander Gordeev
2013-05-29 20:58 ` Bjorn Helgaas
2013-06-03 20:46 ` Bjorn Helgaas
2013-06-04 13:14 ` Alexander Gordeev
2013-06-05 17:18 ` Bjorn Helgaas
2013-06-05 18:33 ` Konrad Rzeszutek Wilk
2013-06-05 18:35 ` Bjorn Helgaas
2013-06-20 12:51 ` Joerg Roedel
2013-06-25 17:34 ` Bjorn Helgaas
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=20130528095052.GA6764@gmail.com \
--to=mingo@kernel.org \
--cc=JBeulich@suse.com \
--cc=agordeev@redhat.com \
--cc=bhelgaas@google.com \
--cc=joro@8bytes.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-pci@vger.kernel.org \
--cc=mingo@redhat.com \
--cc=suresh.b.siddha@intel.com \
--cc=x86@kernel.org \
--cc=yinghai@kernel.org \
/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).