From: Alex Williamson <alex.williamson@redhat.com>
To: Cao jin <caoj.fnst@cn.fujitsu.com>
Cc: <linux-kernel@vger.kernel.org>, <kvm@vger.kernel.org>,
<izumi.taku@jp.fujitsu.com>, <mst@redhat.com>
Subject: Re: [PATCH] vfio/pci: Support error recovery
Date: Sun, 4 Dec 2016 08:30:47 -0700 [thread overview]
Message-ID: <20161204083047.7e715b09@t450s.home> (raw)
In-Reply-To: <5844092A.30204@cn.fujitsu.com>
On Sun, 4 Dec 2016 20:16:42 +0800
Cao jin <caoj.fnst@cn.fujitsu.com> wrote:
> On 12/01/2016 10:55 PM, Alex Williamson wrote:
> > On Thu, 1 Dec 2016 21:40:00 +0800
>
> >>> If an AER fault occurs and the user doesn't do a reset, what
> >>> happens when that device is released and a host driver tries to make
> >>> use of it? The user makes no commitment to do a reset and there are
> >>> only limited configurations where we even allow the user to perform a
> >>> reset.
> >>>
> >>
> >> Limited? Do you mean the things __pci_dev_reset() can do?
> >
> > I mean that there are significant device and guest configuration
> > restrictions in order to support AER. For instance, all the functions
> > of the slot need to appear in a PCI-e topology in the guest with all
> > the functions in the right place such that a guest bus reset translates
> > into a host bus reset. The physical functions cannot be split between
> > guests even if IOMMU isolation would otherwise allow it. The user
> > needs to explicitly enable AER support for the devices. A VM need to
> > be specifically configured for AER support in order to set any sort of
> > expectations of a guest directed bus reset, let alone a guarantee that
> > it will happen. So all the existing VMs, where functions are split
> > between guests, or the topology isn't exactly right, or AER isn't
> > enabled see a regression from the above change as the device is no
> > longer reset.
> >
>
> I am not clear why set these restrictions in the current design. I take
> a glance at older versions of qemu's patchset, their thoughts is:
> translate a guest bus reset into a host bus reset(Which is
> unreasonable[*] to me). And I guess, that's the *cause* of these
> restrictions? Is there any other stories behind these restrictions?
>
> [*] In physical world, set bridge's secondary bus reset would send
> hot-reset TLP to all functions below, trigger every device's reset
> separately. Emulated device should behave the same, means just using
> each device's DeviceClass->reset method.
Are you trying to say that an FLR is equivalent to a link reset?
Please go read the previous discussions, especially if you're sending
patches you don't believe in. Thanks,
Alex
next prev parent reply other threads:[~2016-12-04 15:30 UTC|newest]
Thread overview: 52+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-11-27 11:34 [PATCH] vfio/pci: Support error recovery Cao jin
2016-11-28 3:00 ` Michael S. Tsirkin
2016-11-28 9:32 ` Cao jin
2016-11-30 1:46 ` Michael S. Tsirkin
2016-12-01 13:38 ` Cao jin
2016-12-01 4:04 ` Alex Williamson
2016-12-01 4:51 ` Michael S. Tsirkin
2016-12-01 13:40 ` Cao jin
2016-12-06 3:46 ` Michael S. Tsirkin
2016-12-06 6:47 ` Cao jin
2016-12-01 13:40 ` Cao jin
2016-12-01 14:55 ` Alex Williamson
2016-12-04 12:16 ` Cao jin
2016-12-04 15:30 ` Alex Williamson [this message]
2016-12-05 5:52 ` Cao jin
2016-12-05 16:17 ` Alex Williamson
2016-12-06 3:55 ` Michael S. Tsirkin
2016-12-06 4:59 ` Alex Williamson
2016-12-06 10:46 ` Cao jin
2016-12-06 15:35 ` Alex Williamson
2016-12-07 2:49 ` Cao jin
2016-12-08 14:46 ` Cao jin
2016-12-08 16:30 ` Michael S. Tsirkin
2016-12-09 3:40 ` Cao jin
2016-12-09 3:40 ` Cao jin
2016-12-06 6:11 ` Cao jin
2016-12-06 15:25 ` Alex Williamson
2016-12-07 2:58 ` Cao jin
2016-12-12 13:49 ` Cao jin
2016-12-12 19:12 ` Alex Williamson
2016-12-12 22:29 ` Michael S. Tsirkin
2016-12-12 22:43 ` Alex Williamson
2016-12-13 3:15 ` Michael S. Tsirkin
2016-12-13 3:39 ` Alex Williamson
2016-12-13 16:12 ` Michael S. Tsirkin
2016-12-13 16:27 ` Alex Williamson
2016-12-14 1:58 ` Michael S. Tsirkin
2016-12-14 3:00 ` Alex Williamson
2016-12-14 22:20 ` Michael S. Tsirkin
2016-12-14 22:47 ` Alex Williamson
2016-12-14 23:00 ` Michael S. Tsirkin
2016-12-14 23:32 ` Alex Williamson
2016-12-14 10:24 ` Cao jin
2016-12-14 22:16 ` Alex Williamson
2016-12-14 22:25 ` Michael S. Tsirkin
2016-12-14 22:49 ` Alex Williamson
2016-12-15 13:56 ` Cao jin
2016-12-15 14:50 ` Michael S. Tsirkin
2016-12-15 22:01 ` Alex Williamson
2016-12-16 10:15 ` Cao jin
2016-12-16 10:15 ` Cao jin
2016-12-15 17:02 ` Alex Williamson
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