From 24b36e9813ec15da7db62e3b3621730710c5f020 Mon Sep 17 00:00:00 2001 From: Paolo Bonzini Date: Thu, 3 Jun 2021 10:34:23 +0200 Subject: block: add max_hw_transfer to BlockLimits For block host devices, I/O can happen through either the kernel file descriptor I/O system calls (preadv/pwritev, io_submit, io_uring) or the SCSI passthrough ioctl SG_IO. In the latter case, the size of each transfer can be limited by the HBA, while for file descriptor I/O the kernel is able to split and merge I/O in smaller pieces as needed. Applying the HBA limits to file descriptor I/O results in more system calls and suboptimal performance, so this patch splits the max_transfer limit in two: max_transfer remains valid and is used in general, while max_hw_transfer is limited to the maximum hardware size. max_hw_transfer can then be included by the scsi-generic driver in the block limits page, to ensure that the stricter hardware limit is used. Signed-off-by: Paolo Bonzini --- hw/scsi/scsi-generic.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'hw/scsi') diff --git a/hw/scsi/scsi-generic.c b/hw/scsi/scsi-generic.c index b6c4143..665baf9 100644 --- a/hw/scsi/scsi-generic.c +++ b/hw/scsi/scsi-generic.c @@ -179,7 +179,7 @@ static int scsi_handle_inquiry_reply(SCSIGenericReq *r, SCSIDevice *s, int len) (r->req.cmd.buf[1] & 0x01)) { page = r->req.cmd.buf[2]; if (page == 0xb0) { - uint32_t max_transfer = blk_get_max_transfer(s->conf.blk); + uint64_t max_transfer = blk_get_max_hw_transfer(s->conf.blk); uint32_t max_iov = blk_get_max_iov(s->conf.blk); assert(max_transfer); -- cgit v1.1