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[PATCH v2 3/5] block: add max_ioctl_transfer to BlockLimits
From: |
Maxim Levitsky |
Subject: |
[PATCH v2 3/5] block: add max_ioctl_transfer to BlockLimits |
Date: |
Wed, 9 Dec 2020 15:53:53 +0200 |
Maximum transfer size when accessing a kernel block device is only relevant
when using SCSI passthrough (SG_IO ioctl) since only in this case the requests
are passed directly to underlying hardware with no pre-processing.
Same is true when using /dev/sg* character devices (which only support SG_IO)
Therefore split the block driver's advertized max transfer size by
the regular max transfer size, and the max transfer size for SCSI passthrough
(the new max_ioctl_transfer field)
In the next patch, the qemu block drivers that support SCSI passthrough
will set the max_ioctl_transfer field, and simultaneously, the block devices
that implement scsi passthrough will switch to 'blk_get_max_ioctl_transfer' to
query and to pass it to the guest.
Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
---
block/block-backend.c | 12 ++++++++++++
block/io.c | 2 ++
include/block/block_int.h | 4 ++++
include/sysemu/block-backend.h | 1 +
4 files changed, 19 insertions(+)
diff --git a/block/block-backend.c b/block/block-backend.c
index ce78d30794..c1d149a755 100644
--- a/block/block-backend.c
+++ b/block/block-backend.c
@@ -1938,6 +1938,18 @@ uint32_t blk_get_max_transfer(BlockBackend *blk)
return MIN_NON_ZERO(max, INT_MAX);
}
+/* Returns the maximum transfer length, for SCSI passthrough */
+uint32_t blk_get_max_ioctl_transfer(BlockBackend *blk)
+{
+ BlockDriverState *bs = blk_bs(blk);
+ uint32_t max = 0;
+
+ if (bs) {
+ max = bs->bl.max_ioctl_transfer;
+ }
+ return MIN_NON_ZERO(max, INT_MAX);
+}
+
int blk_get_max_iov(BlockBackend *blk)
{
return blk->root->bs->bl.max_iov;
diff --git a/block/io.c b/block/io.c
index ec5e152bb7..3eae176992 100644
--- a/block/io.c
+++ b/block/io.c
@@ -126,6 +126,8 @@ static void bdrv_merge_limits(BlockLimits *dst, const
BlockLimits *src)
{
dst->opt_transfer = MAX(dst->opt_transfer, src->opt_transfer);
dst->max_transfer = MIN_NON_ZERO(dst->max_transfer, src->max_transfer);
+ dst->max_ioctl_transfer = MIN_NON_ZERO(dst->max_ioctl_transfer,
+ src->max_ioctl_transfer);
dst->opt_mem_alignment = MAX(dst->opt_mem_alignment,
src->opt_mem_alignment);
dst->min_mem_alignment = MAX(dst->min_mem_alignment,
diff --git a/include/block/block_int.h b/include/block/block_int.h
index 95d9333be1..e9874c8c23 100644
--- a/include/block/block_int.h
+++ b/include/block/block_int.h
@@ -678,6 +678,10 @@ typedef struct BlockLimits {
* clamped down. */
uint32_t max_transfer;
+ /* Maximal transfer length for SCSI passthrough (ioctl interface) */
+ uint32_t max_ioctl_transfer;
+
+
/* memory alignment, in bytes so that no bounce buffer is needed */
size_t min_mem_alignment;
diff --git a/include/sysemu/block-backend.h b/include/sysemu/block-backend.h
index 8203d7f6f9..b019a37b7a 100644
--- a/include/sysemu/block-backend.h
+++ b/include/sysemu/block-backend.h
@@ -203,6 +203,7 @@ void blk_eject(BlockBackend *blk, bool eject_flag);
int blk_get_flags(BlockBackend *blk);
uint32_t blk_get_request_alignment(BlockBackend *blk);
uint32_t blk_get_max_transfer(BlockBackend *blk);
+uint32_t blk_get_max_ioctl_transfer(BlockBackend *blk);
int blk_get_max_iov(BlockBackend *blk);
void blk_set_guest_block_size(BlockBackend *blk, int align);
void *blk_try_blockalign(BlockBackend *blk, size_t size);
--
2.26.2
- [PATCH v2 0/5] SCSI: fix transfer limits for SCSI passthrough, Maxim Levitsky, 2020/12/09
- [PATCH v2 1/5] file-posix: split hdev_refresh_limits from raw_refresh_limits, Maxim Levitsky, 2020/12/09
- [PATCH v2 2/5] file-posix: add sg_get_max_segments that actually works with sg, Maxim Levitsky, 2020/12/09
- [PATCH v2 3/5] block: add max_ioctl_transfer to BlockLimits,
Maxim Levitsky <=
- [PATCH v2 4/5] block: use blk_get_max_ioctl_transfer for SCSI passthrough, Maxim Levitsky, 2020/12/09
- [PATCH v2 5/5] block/scsi: correctly emulate the VPD block limits page, Maxim Levitsky, 2020/12/09
- Re: [PATCH v2 0/5] SCSI: fix transfer limits for SCSI passthrough, no-reply, 2020/12/09