From: Gerd Hoffmann <kraxel@redhat.com>
To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: qemu-devel@nongnu.org, Anthony Liguori <aliguori@amazon.com>
Subject: Re: [Qemu-devel] [RfC PATCH] virtio-pci: place msix regions in modern virtio bar
Date: Fri, 23 Jan 2015 14:53:27 +0100 [thread overview]
Message-ID: <1422021207.13166.38.camel@nilsson.home.kraxel.org> (raw)
In-Reply-To: <20150123133341.GD4579@redhat.com>
Hi,
> I wanted to make the modern BAR prefetcheable, so it can
> be a full 64-bit one,
It's not the case right now though, the two bars have identical
attributes, and there is plenty of unused space in the modern virtio
bar ...
> this is impossible with the MSI-X
> BAR.
What exactly is impossible? msi-x being in a 64bit bar? msi-x being in
a prefetchable bar? Also why the bar needs to be prefetchable to be
64bit bit?
xhci looks this way right now:
00:0f.0 USB controller: NEC Corporation uPD720200 USB 3.0 Host
Controller (rev 03) (prog-if 30 [XHCI])
Subsystem: Red Hat, Inc QEMU Virtual Machine
Physical Slot: 15
Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr-
Stepping- SERR+ FastB2B- DisINTx+
Status: Cap+ 66MHz- UDF- FastB2B- ParErr- DEVSEL=fast >TAbort- <TAbort-
<MAbort- >SERR- <PERR- INTx-
Latency: 0, Cache Line Size: 64 bytes
Interrupt: pin A routed to IRQ 10
Region 0: Memory at febd0000 (64-bit, non-prefetchable) [size=16K]
Capabilities: [90] MSI-X: Enable+ Count=16 Masked-
Vector table: BAR=0 offset=00003000
PBA: BAR=0 offset=00003800
Capabilities: [70] MSI: Enable- Count=1/16 Maskable- 64bit+
Address: 0000000000000000 Data: 0000
Kernel driver in use: xhci_hcd
Which works just fine even with msi-x in a 64-bit (non-prefetchable)
bar, but maybe just by pure luck? Also seabios wouldn't map the bar
above 4G.
cheers,
Gerd
next prev parent reply other threads:[~2015-01-23 13:53 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-01-23 12:29 [Qemu-devel] [RfC PATCH] virtio-pci: place msix regions in modern virtio bar Gerd Hoffmann
2015-01-23 13:33 ` Michael S. Tsirkin
2015-01-23 13:53 ` Gerd Hoffmann [this message]
2015-01-23 13:58 ` Michael S. Tsirkin
2015-01-23 14:48 ` Gerd Hoffmann
2015-01-23 15:12 ` Michael S. Tsirkin
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=1422021207.13166.38.camel@nilsson.home.kraxel.org \
--to=kraxel@redhat.com \
--cc=aliguori@amazon.com \
--cc=mst@redhat.com \
--cc=qemu-devel@nongnu.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).