Re: [Qemu-devel] [PATCH 07/11] blockdev: flip default cache mode from writethrough to writeback

2013-03-27 Thread Artyom Tarasenko 
On Fri, Aug 10, 2012 at 6:47 PM, Kevin Wolf kw...@redhat.com wrote:
 From: Paolo Bonzini pbonz...@redhat.com

 Now all major device models (IDE, SCSI, virtio) can choose between
 writethrough and writeback at run-time, and virtio will even revert
 to writethrough if the guest is not capable of sending flushes.  So
 we can change the default to writeback at last.

 Tested, for lack of a better idea, with a breakpoint on bdrv_open
 and all cache choices one by one.

This patch breaks shutting down of a sparc32 guest (or at least the
Debian-4 image I have):

$ sparc-softmmu/qemu-system-sparc -M SS-5 -nographic -hda  ../disk-debian-4
[...]
Debian GNU/Linux 4.0 debian ttyS0

debian login: root
Password:
Linux debian 2.6.18-6-sparc32 #1 Tue Nov 10 00:31:37 UTC 2009 sparc
# poweroff
[...]
Will now halt.
Synchronizing SCSI cache for disk sda:
esp0: Aborting command
esp0: dumping state
esp0: dma -- cond_rega4400010 addrf00b
esp0: SW [sreg03 sstep04 ireg10]
esp0: HW reread [sreg03 sstep00 ireg08]
esp0: current command [tgt00 lun00 pphaseMSGINDONE cphaseCLUELESS]
esp0: disconnected
esp0: Aborting command
esp0: dumping state
esp0: dma -- cond_rega4400010 addrf00b
esp0: SW [sreg03 sstep04 ireg10]
esp0: HW reread [sreg03 sstep04 ireg00]
esp0: current command [tgt00 lun00 pphaseUNISSUED cphaseUNISSUED]
esp0: disconnected
esp0: Resetting scsi bus
esp0: SCSI bus reset interrupt
esp0: no command in esp_handle()
Kernel panic - not syncing: esp_handle: current_SC == penguin within interrupt!
 0Press Stop-A (L1-A) to return to the boot prom


Without the patch, the line Synchronizing SCSI cache for disk sda
doesn't come up, so the patch probably just unveils a bug somewhere
else (esp?).

 Signed-off-by: Paolo Bonzini pbonz...@redhat.com
 Signed-off-by: Kevin Wolf kw...@redhat.com
 ---
  blockdev.c |1 +
  1 files changed, 1 insertions(+), 0 deletions(-)

 diff --git a/blockdev.c b/blockdev.c
 index 8669142..7c83baa 100644
 --- a/blockdev.c
 +++ b/blockdev.c
 @@ -377,6 +377,7 @@ DriveInfo *drive_init(QemuOpts *opts, int default_to_scsi)
 }
  }

 +bdrv_flags |= BDRV_O_CACHE_WB;
  if ((buf = qemu_opt_get(opts, cache)) != NULL) {
  if (bdrv_parse_cache_flags(buf, bdrv_flags) != 0) {
  error_report(invalid cache option);
 --
 1.7.6.5





-- 
Regards,
Artyom Tarasenko

linux/sparc and solaris/sparc under qemu blog:
http://tyom.blogspot.com/search/label/qemu

Re: [Qemu-devel] [PATCH 07/11] blockdev: flip default cache mode from writethrough to writeback

2013-03-27 Thread Paolo Bonzini 
Il 27/03/2013 16:16, Artyom Tarasenko ha scritto:
 This patch breaks shutting down of a sparc32 guest (or at least the
 Debian-4 image I have):
 
 $ sparc-softmmu/qemu-system-sparc -M SS-5 -nographic -hda  ../disk-debian-4
 [...]
 Debian GNU/Linux 4.0 debian ttyS0
 
 debian login: root
 Password:
 Linux debian 2.6.18-6-sparc32 #1 Tue Nov 10 00:31:37 UTC 2009 sparc
 # poweroff
 [...]
 Will now halt.
 Synchronizing SCSI cache for disk sda:
 esp0: Aborting command
 esp0: dumping state
 esp0: dma -- cond_rega4400010 addrf00b
 esp0: SW [sreg03 sstep04 ireg10]
 esp0: HW reread [sreg03 sstep00 ireg08]
 esp0: current command [tgt00 lun00 pphaseMSGINDONE cphaseCLUELESS]
 esp0: disconnected
 esp0: Aborting command
 esp0: dumping state
 esp0: dma -- cond_rega4400010 addrf00b
 esp0: SW [sreg03 sstep04 ireg10]
 esp0: HW reread [sreg03 sstep04 ireg00]
 esp0: current command [tgt00 lun00 pphaseUNISSUED cphaseUNISSUED]
 esp0: disconnected
 esp0: Resetting scsi bus
 esp0: SCSI bus reset interrupt
 esp0: no command in esp_handle()
 Kernel panic - not syncing: esp_handle: current_SC == penguin within 
 interrupt!
  0Press Stop-A (L1-A) to return to the boot prom
 
 
 Without the patch, the line Synchronizing SCSI cache for disk sda
 doesn't come up, so the patch probably just unveils a bug somewhere
 else (esp?).

It doesn't come up because, with a writethrough cache, there is no need
to flush the cache.  The bug should be reproducible before this patch
with -drive file=../disk-debian-4,cache=writeback.

Paolo

[Qemu-devel] [PATCH 07/11] blockdev: flip default cache mode from writethrough to writeback

2012-08-10 Thread Kevin Wolf 
From: Paolo Bonzini pbonz...@redhat.com

Now all major device models (IDE, SCSI, virtio) can choose between
writethrough and writeback at run-time, and virtio will even revert
to writethrough if the guest is not capable of sending flushes.  So
we can change the default to writeback at last.

Tested, for lack of a better idea, with a breakpoint on bdrv_open
and all cache choices one by one.

Signed-off-by: Paolo Bonzini pbonz...@redhat.com
Signed-off-by: Kevin Wolf kw...@redhat.com
---
 blockdev.c |1 +
 1 files changed, 1 insertions(+), 0 deletions(-)

diff --git a/blockdev.c b/blockdev.c
index 8669142..7c83baa 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -377,6 +377,7 @@ DriveInfo *drive_init(QemuOpts *opts, int default_to_scsi)
}
 }
 
+bdrv_flags |= BDRV_O_CACHE_WB;
 if ((buf = qemu_opt_get(opts, cache)) != NULL) {
 if (bdrv_parse_cache_flags(buf, bdrv_flags) != 0) {
 error_report(invalid cache option);
-- 
1.7.6.5