From: Peter Xu <peterx@redhat.com>
To: Jason Wang <jasowang@redhat.com>
Cc: eperezma@redhat.com, qemu-stable@nongnu.org,
qemu-devel@nongnu.org, mst@redhat.com
Subject: Re: [PATCH] pci: advertise a page aligned ATS
Date: Thu, 10 Sep 2020 12:23:41 -0400 [thread overview]
Message-ID: <20200910162341.GD247092@xz-x1> (raw)
In-Reply-To: <b343fea6-ecf2-7605-9340-decdd1b95149@redhat.com>
On Thu, Sep 10, 2020 at 09:53:03AM +0800, Jason Wang wrote:
> > Maybe it would be good too that vhost provides real 4k-aligned addresses (in
> > vhost_iotlb_miss)? My understanding is that PCI_ATS_CAP_PAGE_ALIGNED will be
> > more compatible than without the bit set.
>
>
> Yes, I've considered this. But the problem is that:
>
> 1) vhost itself can generate unaligned request (since its IOTLB doesn't have
> any alignment requirement)
> 2) the IOTLB miss processing in qemu doesn't do anything with ATS, we
> shortcut PCI by calling the address_space_get_iotlb_entry()
>
> So I'm not quite sure it's worth to do that consider we don't emulate ATS
> via PCI actually :)
True. :) Though we still need to make sure e.g. each translate() iommu op will
drop those bits properly, but I agree that should be trivial.
--
Peter Xu
next prev parent reply other threads:[~2020-09-10 16:24 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-09 8:17 [PATCH] pci: advertise a page aligned ATS Jason Wang
2020-09-09 15:43 ` Peter Xu
2020-09-10 1:53 ` Jason Wang
2020-09-10 16:23 ` Peter Xu [this message]
2020-10-15 7:47 ` Jason Wang
2020-10-15 13:10 ` Michael S. Tsirkin
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