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From: Thomas Gleixner <tglx@linutronix.de>
To: Alex Williamson <alex.williamson@redhat.com>
Cc: Jan Kiszka <jan.kiszka@siemens.com>,
	Richard Weinberger <richard@nod.at>,
	kvm@vger.kernel.org, avi@redhat.com,
	Marcelo Tosatti <mtosatti@redhat.com>,
	Bjorn Helgaas <bhelgaas@google.com>,
	"Michael S. Tsirkin" <mst@redhat.com>
Subject: Re: [PATCH 2/2] Device assignment: Fix MSI IRQ affinity setting
Date: Fri, 25 May 2012 01:56:09 +0200 (CEST)	[thread overview]
Message-ID: <alpine.LFD.2.02.1205250149470.3231@ionos> (raw)
In-Reply-To: <1337901828.4714.82.camel@ul30vt>

On Thu, 24 May 2012, Alex Williamson wrote:

> On Fri, 2012-05-25 at 01:01 +0200, Thomas Gleixner wrote:
> > So the proper fix is that qemu tells the guest that mask bit is
> > supported and catches the mask bit toggling before writing it out to
> > the hardware for those devices which do not support it.
> 
> We can't necessarily do that, we have to work with the config space
> we're give.  Using the smallest possible MSI capability always works.
> Adding mask bits may not fit in with the existing capabilities of the
> physical device.  Thanks,

I see what you mean. A random device driver of a random guest OS might
rely on that information. Unlikely, but ....

So we need some logic to circumvent the masked/unmasked logic in case
that property is not set, right ?

Thanks,

	tglx

  reply	other threads:[~2012-05-24 23:56 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-05-24 17:02 [PATCH 1/2] Remove kvm_commit_irq_routes from error messages Richard Weinberger
2012-05-24 17:02 ` [PATCH 2/2] Device assignment: Fix MSI IRQ affinity setting Richard Weinberger
2012-05-24 18:20   ` Alex Williamson
     [not found]     ` <CAEMbtc+ycsC6u=CZ_Yg6C=WV=VqjA2uEDM5KWPM_7n3sZh_9Pw@mail.gmail.com>
2012-05-24 19:27       ` Richard Weinberger
2012-05-24 21:39     ` Thomas Gleixner
2012-05-24 21:53       ` Jan Kiszka
2012-05-24 22:11         ` Alex Williamson
2012-05-24 23:01           ` Thomas Gleixner
2012-05-24 23:23             ` Alex Williamson
2012-05-24 23:56               ` Thomas Gleixner [this message]
2012-05-25  2:37                 ` Jan Kiszka
2012-05-24 22:17         ` Michael S. Tsirkin
2012-05-24 23:06           ` Thomas Gleixner
2012-05-24 23:19             ` Thomas Gleixner
2012-05-24 22:05       ` Alex Williamson
2012-05-24 20:47   ` Jan Kiszka

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