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[Qemu-devel] [RFC PATCH 3/3] block: do not rely on the buffer alignment
From: |
Paolo Bonzini |
Subject: |
[Qemu-devel] [RFC PATCH 3/3] block: do not rely on the buffer alignment passed to the guest |
Date: |
Wed, 23 Nov 2011 17:51:27 +0100 |
The guest alignment should not override the host's. Instead, just use
the bdrv_set_buffer_alignment calls to print a warning about possible
performance degradations due to insufficiently-aligned guest buffers.
Signed-off-by: Paolo Bonzini <address@hidden>
---
block.c | 8 ++++++--
block.h | 2 +-
hw/ide/core.c | 2 +-
hw/scsi-disk.c | 2 +-
hw/scsi-generic.c | 1 -
hw/virtio-blk.c | 2 +-
6 files changed, 10 insertions(+), 7 deletions(-)
diff --git a/block.c b/block.c
index aba92ad..cd11344 100644
--- a/block.c
+++ b/block.c
@@ -3039,9 +3039,13 @@ BlockDriverAIOCB *bdrv_aio_ioctl(BlockDriverState *bs,
return NULL;
}
-void bdrv_set_buffer_alignment(BlockDriverState *bs, int align)
+void bdrv_check_buffer_alignment(BlockDriverState *bs, int align)
{
- bs->buffer_alignment = align;
+ if ((bs->open_flags & BDRV_O_NOCACHE) && bdrv_get_alignment(bs) > align) {
+ error_report("Host block size is %d, guest block size is %d.\n"
+ "cache=none may cause performance degradation.",
+ bdrv_get_alignment(bs), align);
+ }
}
void *qemu_blockalign(BlockDriverState *bs, size_t size)
diff --git a/block.h b/block.h
index 5fa632c..386284c 100644
--- a/block.h
+++ b/block.h
@@ -295,7 +295,7 @@ int bdrv_img_create(const char *filename, const char *fmt,
char *options, uint64_t img_size, int flags);
int bdrv_get_alignment(BlockDriverState *bs);
-void bdrv_set_buffer_alignment(BlockDriverState *bs, int align);
+void bdrv_check_buffer_alignment(BlockDriverState *bs, int align);
void *qemu_blockalign(BlockDriverState *bs, size_t size);
#define BDRV_SECTORS_PER_DIRTY_CHUNK 2048
diff --git a/hw/ide/core.c b/hw/ide/core.c
index 93a1a68..3b8cdb2 100644
--- a/hw/ide/core.c
+++ b/hw/ide/core.c
@@ -1863,7 +1863,7 @@ int ide_init_drive(IDEState *s, BlockDriverState *bs,
IDEDriveKind kind,
s->smart_selftest_count = 0;
if (kind == IDE_CD) {
bdrv_set_dev_ops(bs, &ide_cd_block_ops, s);
- bdrv_set_buffer_alignment(bs, 2048);
+ bdrv_check_buffer_alignment(bs, 2048);
} else {
if (!bdrv_is_inserted(s->bs)) {
error_report("Device needs media, but drive is empty");
diff --git a/hw/scsi-disk.c b/hw/scsi-disk.c
index 673948c..946d670 100644
--- a/hw/scsi-disk.c
+++ b/hw/scsi-disk.c
@@ -1553,7 +1553,7 @@ static int scsi_initfn(SCSIDevice *dev)
if (s->removable) {
bdrv_set_dev_ops(s->qdev.conf.bs, &scsi_cd_block_ops, s);
}
- bdrv_set_buffer_alignment(s->qdev.conf.bs, s->qdev.blocksize);
+ bdrv_check_buffer_alignment(s->qdev.conf.bs, s->qdev.blocksize);
bdrv_iostatus_enable(s->qdev.conf.bs);
add_boot_device_path(s->qdev.conf.bootindex, &dev->qdev, NULL);
diff --git a/hw/scsi-generic.c b/hw/scsi-generic.c
index 9594cc1..c681a37 100644
--- a/hw/scsi-generic.c
+++ b/hw/scsi-generic.c
@@ -188,7 +188,6 @@ static void scsi_read_complete(void * opaque, int ret)
s->blocksize = ldl_be_p(&r->buf[8]);
s->max_lba = ldq_be_p(&r->buf[0]);
}
- bdrv_set_buffer_alignment(s->conf.bs, s->blocksize);
scsi_req_data(&r->req, len);
if (!r->req.io_canceled) {
diff --git a/hw/virtio-blk.c b/hw/virtio-blk.c
index 91c92b2..ddc8b15 100644
--- a/hw/virtio-blk.c
+++ b/hw/virtio-blk.c
@@ -624,7 +624,7 @@ VirtIODevice *virtio_blk_init(DeviceState *dev, BlockConf
*conf,
register_savevm(dev, "virtio-blk", virtio_blk_id++, 2,
virtio_blk_save, virtio_blk_load, s);
bdrv_set_dev_ops(s->bs, &virtio_block_ops, s);
- bdrv_set_buffer_alignment(s->bs, conf->logical_block_size);
+ bdrv_check_buffer_alignment(s->bs, conf->logical_block_size);
bdrv_iostatus_enable(s->bs);
add_boot_device_path(conf->bootindex, dev, "/address@hidden,0");
--
1.7.7.1