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scsi-generic: pass max_segments via max_iov field in BlockLimits
I/O to a disk via read/write is not limited by the number of segments allowed by the host adapter; the kernel can split requests if needed, and the limit imposed by the host adapter can be very low (256k or so) to avoid that SG_IO returns EINVAL if memory is heavily fragmented. Since this value is only interesting for SG_IO-based I/O, do not include it in the max_transfer and only take it into account when patching the block limits VPD page in the scsi-generic device. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Reviewed-by: Max Reitz <mreitz@redhat.com>
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@ -1237,8 +1237,7 @@ static void raw_refresh_limits(BlockDriverState *bs, Error **errp)
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ret = sg_get_max_segments(s->fd);
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if (ret > 0) {
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bs->bl.max_transfer = MIN(bs->bl.max_transfer,
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ret * qemu_real_host_page_size);
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bs->bl.max_iov = ret;
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}
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}
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@ -179,10 +179,12 @@ static int scsi_handle_inquiry_reply(SCSIGenericReq *r, SCSIDevice *s, int len)
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(r->req.cmd.buf[1] & 0x01)) {
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page = r->req.cmd.buf[2];
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if (page == 0xb0) {
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uint32_t max_transfer =
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blk_get_max_transfer(s->conf.blk) / s->blocksize;
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uint32_t max_transfer = blk_get_max_transfer(s->conf.blk);
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uint32_t max_iov = blk_get_max_iov(s->conf.blk);
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assert(max_transfer);
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max_transfer = MIN_NON_ZERO(max_transfer, max_iov * qemu_real_host_page_size)
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/ s->blocksize;
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stl_be_p(&r->buf[8], max_transfer);
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/* Also take care of the opt xfer len. */
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stl_be_p(&r->buf[12],
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