From: Paolo Bonzini <pbonzini@redhat.com>
To: Cong Meng <mc@linux.vnet.ibm.com>
Cc: stefanha@linux.vnet.ibm.com, Stefan Hajnoczi <stefanha@gmail.com>,
zwanp@cn.ibm.com, linuxram@us.ibm.com, qemu-devel@nongnu.org,
virtualization@lists.linux-foundation.org
Subject: Re: [Qemu-devel] [PATCH 1/2 v1] blkdrv: Add queue limits parameters for sg block drive
Date: Wed, 22 Aug 2012 14:09:28 +0200 [thread overview]
Message-ID: <5034CBF8.3050602@redhat.com> (raw)
In-Reply-To: <5034BCD1.9020603@linux.vnet.ibm.com>
Il 22/08/2012 13:04, Cong Meng ha scritto:
>>
>> Cong, what is the limit that the host HBA enforces (and what is the
>> HBA)? What commands see a problem? Is it fixed by using scsi-block
>> instead of scsi-generic (if you can use scsi-block at all, i.e. it's not
>> a tape or similar device)?
>>
> I don't see real problem caused by the the queue limits actually. It's a
> bug which Stefan told me.
I'd rather avoid patching the specification if not to solve real (rather
than known-but-theoretical) problems.
>> With scsi-generic, QEMU uses a bounce buffer for non-I/O commands to a
>> SCSI passthrough device, so the only problem in that case should be the
>> maximum segment size. This could change in the future, but max_segments
>> and max_sectors should not yet be a problem.
>
> about bounce buffer, do you meat the buffer allocated in
> scsi_send_command() of hw/scsi-generic.c?
Yes.
Paolo
next prev parent reply other threads:[~2012-08-22 12:09 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-08-21 8:23 [Qemu-devel] [PATCH 1/2 v1] blkdrv: Add queue limits parameters for sg block drive Cong Meng
2012-08-21 8:23 ` [Qemu-devel] [PATCH 2/2 v1] virtio-scsi: set per-LUN queue limits for sg devices Cong Meng
2012-08-21 9:56 ` Stefan Hajnoczi
2012-08-21 8:48 ` [Qemu-devel] [PATCH 1/2 v1] blkdrv: Add queue limits parameters for sg block drive Paolo Bonzini
2012-08-21 9:41 ` Cong Meng
2012-08-21 9:52 ` Stefan Hajnoczi
2012-08-21 10:14 ` Paolo Bonzini
2012-08-22 11:04 ` Cong Meng
2012-08-22 12:09 ` Paolo Bonzini [this message]
2012-08-22 13:13 ` Stefan Hajnoczi
2012-08-22 14:13 ` Paolo Bonzini
2012-08-23 9:31 ` Cong Meng
2012-08-23 10:03 ` Paolo Bonzini
2012-08-23 10:08 ` Stefan Hajnoczi
2012-08-23 10:52 ` Paolo Bonzini
2012-08-23 12:08 ` Stefan Hajnoczi
2012-08-24 0:45 ` Nicholas A. Bellinger
2012-08-24 7:56 ` Paolo Bonzini
2012-08-24 10:43 ` Hannes Reinecke
2012-08-24 9:05 ` Stefan Hajnoczi
2012-08-24 9:14 ` Paolo Bonzini
2012-08-21 9:49 ` Stefan Hajnoczi
2012-08-21 18:31 ` Blue Swirl
2012-08-22 8:25 ` Stefan Hajnoczi
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