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From b514fee67a81636d71e4598ab8a1bcc64459f7b2 Mon Sep 17 00:00:00 2001
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Message-Id: <b514fee67a81636d71e4598ab8a1bcc64459f7b2@dist-git>
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From: Eric Blake <eblake@redhat.com>
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Date: Wed, 29 Oct 2014 15:15:23 -0600
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Subject: [PATCH] qemu: better error message when block job can't succeed
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https://bugzilla.redhat.com/show_bug.cgi?id=1140981 reports that
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the qemu-kvm shipped as part of RHEL 7.0 intentionally[1] cripples
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block jobs by removing the 'block-stream' QMP command, while still
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leaving 'block-job-cancel' as an unusable no-op. Meanwhile, we
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already had existing code that checked whether block jobs were
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completely missing (such as qemu 0.15), old style (cancel is
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synchronous, and all commands spelled with '_'), or new style
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(cancel is asynchronous, and all commands spelled with '-'), and
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used that three-way probe to give decent error messages. At the
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time that code was added, all existing qemu versions fell in one
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of three buckets, and the code was using the presence of
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'block-job-cancel' as the witness of which of the three buckets.
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But now that RHEL qemu has shipped with intentionally crippled
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'block-stream', we have a fourth bucket, which results in ugly
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error messages when trying 'virsh blockpull':
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error: Requested operation is not valid: Command 'block-stream' is not found
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In reality, the fourth bucket should be treated the same as the
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first bucket (no block job support); we can do that by realizing
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that no existing build of qemu has working block-stream while
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lacking block-job-cancel, so it is easiest to change our witness
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to the command that starts a job rather than ends one. We still
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act correctly regarding command spelling and whether cancel is
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asynchronous. And on crippled RHEL builds, we now get the desired:
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error: unsupported configuration: block jobs not supported with this qemu binary
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[1] The intentional cripple is limited to qemu-kvm of RHEL; when using
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qemu-kvm-rhev of RHEV, block job functionality is supported. Don't ask
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me to explain the "why" behind it all - I'm just dealing with fallout
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from someone else's decision.
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* src/qemu/qemu_capabilities.h (QEMU_CAPS_BLOCKJOB_SYNC): Tweak comment.
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* src/qemu/qemu_capabilities.c (virQEMUCapsCommands): Look for stream
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rather than cancel when determining the flavor of block jobs supported.
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Signed-off-by: Eric Blake <eblake@redhat.com>
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(cherry picked from commit 00331bfbc9626ee9e94352453087b521943236ca)
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Signed-off-by: Jiri Denemark <jdenemar@redhat.com>
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---
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src/qemu/qemu_capabilities.c | 4 ++--
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src/qemu/qemu_capabilities.h | 4 ++--
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2 files changed, 4 insertions(+), 4 deletions(-)
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diff --git a/src/qemu/qemu_capabilities.c b/src/qemu/qemu_capabilities.c
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index bb804d3..683b882 100644
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--- a/src/qemu/qemu_capabilities.c
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+++ b/src/qemu/qemu_capabilities.c
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@@ -1422,8 +1422,8 @@ struct virQEMUCapsStringFlags {
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struct virQEMUCapsStringFlags virQEMUCapsCommands[] = {
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{ "system_wakeup", QEMU_CAPS_WAKEUP },
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{ "transaction", QEMU_CAPS_TRANSACTION },
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- { "block_job_cancel", QEMU_CAPS_BLOCKJOB_SYNC },
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- { "block-job-cancel", QEMU_CAPS_BLOCKJOB_ASYNC },
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+ { "block_stream", QEMU_CAPS_BLOCKJOB_SYNC },
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+ { "block-stream", QEMU_CAPS_BLOCKJOB_ASYNC },
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{ "dump-guest-memory", QEMU_CAPS_DUMP_GUEST_MEMORY },
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{ "query-spice", QEMU_CAPS_SPICE },
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{ "query-kvm", QEMU_CAPS_KVM },
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diff --git a/src/qemu/qemu_capabilities.h b/src/qemu/qemu_capabilities.h
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index d3a9a0a..08c531d 100644
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--- a/src/qemu/qemu_capabilities.h
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+++ b/src/qemu/qemu_capabilities.h
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@@ -127,8 +127,8 @@ typedef enum {
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QEMU_CAPS_SCSI_DISK_CHANNEL = 87, /* Is scsi-disk.channel available? */
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QEMU_CAPS_SCSI_BLOCK = 88, /* -device scsi-block */
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QEMU_CAPS_TRANSACTION = 89, /* transaction monitor command */
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- QEMU_CAPS_BLOCKJOB_SYNC = 90, /* RHEL 6.2 block_job_cancel */
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- QEMU_CAPS_BLOCKJOB_ASYNC = 91, /* qemu 1.1 block-job-cancel */
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+ QEMU_CAPS_BLOCKJOB_SYNC = 90, /* old block_job_cancel, block_stream */
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+ QEMU_CAPS_BLOCKJOB_ASYNC = 91, /* new block-job-cancel, block-stream */
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QEMU_CAPS_SCSI_CD = 92, /* -device scsi-cd */
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QEMU_CAPS_IDE_CD = 93, /* -device ide-cd */
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QEMU_CAPS_NO_USER_CONFIG = 94, /* -no-user-config */
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--
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2.1.3
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