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Re: [Qemu-devel] [PATCH] scsi-block: Handle error from host devices
From: |
Daniel Henrique Barboza |
Subject: |
Re: [Qemu-devel] [PATCH] scsi-block: Handle error from host devices |
Date: |
Tue, 3 Apr 2018 17:41:24 -0300 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.6.0 |
Hi Fam,
I've tried this patch and found issues when booting a VM using SCSI
passthrough. This is the backtrace from gdb from the segfault that
happens in the middle of kernel boot:
Thread 1 "qemu-system-ppc" received signal SIGSEGV, Segmentation fault.
[Switching to Thread 0x7ffff7ff63a0 (LWP 16830)]
0x0000000000000000 in ?? ()
(gdb) bt
#0 0x0000000000000000 in ?? ()
#1 0x00000001007b8da8 in scsi_block_sgio_cb (opaque=0x10212e580, ret=0)
at /home/danielhb/qemu/hw/scsi/scsi-disk.c:2772
#2 0x0000000100993f68 in blk_aio_complete (acb=0x101909520) at
/home/danielhb/qemu/block/block-backend.c:1331
#3 0x0000000100994ccc in blk_aio_ioctl_entry (opaque=0x101909520) at
/home/danielhb/qemu/block/block-backend.c:1542
#4 0x0000000100ac0954 in coroutine_trampoline (i0=28666944, i1=1) at
/home/danielhb/qemu/util/coroutine-ucontext.c:116
#5 0x00007ffff789574c in makecontext () at
../sysdeps/unix/sysv/linux/powerpc/powerpc64/makecontext.S:136
#6 0x0000000000000000 in ?? ()
The segfault is happening at this line:
static void scsi_block_sgio_cb(void *opaque, int ret)
{
SCSIBlockReq *req = opaque;
if (!ret &&
(req->io_header.status ||
req->io_header.host_status ||
req->io_header.driver_status)) {
ret = -EIO;
}
req->cb(req->cb_opaque, ret); <-----------------
}
This is happening because inside scsi_block_do_sgio you're not setting
req->cb, just req->cb_opaque. Setting req->cb made the VM boot again:
--- a/hw/scsi/scsi-disk.c
+++ b/hw/scsi/scsi-disk.c
@@ -2851,6 +2851,7 @@ static BlockAIOCB *scsi_block_do_sgio(SCSIBlockReq
*req,
io_header->usr_ptr = r;
io_header->flags |= SG_FLAG_DIRECT_IO;
+ req->cb = cb;
req->cb_opaque = opaque;
aiocb = blk_aio_ioctl(s->qdev.conf.blk, SG_IO, io_header,
scsi_block_sgio_cb, req);
Thanks,
Daniel
On 04/02/2018 12:23 AM, Fam Zheng wrote:
The callback of blk_aio_ioctl is not sensible to SCSI errors, so
werror=stop doesn't work if ioctl returns 0 but the scsi status is
error.
Peek at the sg_io_hdr_t fields and amend ret to fix that.
Signed-off-by: Fam Zheng <address@hidden>
---
hw/scsi/scsi-disk.c | 20 +++++++++++++++++++-
1 file changed, 19 insertions(+), 1 deletion(-)
diff --git a/hw/scsi/scsi-disk.c b/hw/scsi/scsi-disk.c
index f5ab767ab5..2c43830586 100644
--- a/hw/scsi/scsi-disk.c
+++ b/hw/scsi/scsi-disk.c
@@ -2651,10 +2651,26 @@ typedef struct SCSIBlockReq {
/* Selected bytes of the original CDB, copied into our own CDB. */
uint8_t cmd, cdb1, group_number;
+ BlockCompletionFunc *cb;
+ void *cb_opaque;
+
/* CDB passed to SG_IO. */
uint8_t cdb[16];
} SCSIBlockReq;
+static void scsi_block_sgio_cb(void *opaque, int ret)
+{
+ SCSIBlockReq *req = opaque;
+
+ if (!ret &&
+ (req->io_header.status ||
+ req->io_header.host_status ||
+ req->io_header.driver_status)) {
+ ret = -EIO;
+ }
+ req->cb(req->cb_opaque, ret);
+}
+
static BlockAIOCB *scsi_block_do_sgio(SCSIBlockReq *req,
int64_t offset, QEMUIOVector *iov,
int direction,
@@ -2734,7 +2750,9 @@ static BlockAIOCB *scsi_block_do_sgio(SCSIBlockReq *req,
io_header->usr_ptr = r;
io_header->flags |= SG_FLAG_DIRECT_IO;
- aiocb = blk_aio_ioctl(s->qdev.conf.blk, SG_IO, io_header, cb, opaque);
+ req->cb_opaque = opaque;
+ aiocb = blk_aio_ioctl(s->qdev.conf.blk, SG_IO, io_header,
+ scsi_block_sgio_cb, req);
assert(aiocb != NULL);
return aiocb;
}