Hi,all
In the vbd blkback driver(linux/drivers/xen/blkback/blkback.c),
when function dispatch_rw_block_io() try to do the real I/O job,
it will do a sanity check on I/O request sent from DomU in the following code
fragment:
...
430 for (i = 0; i < nseg; i++) {
431 uint32_t flags;
432
433 seg[i].nsec = req->seg[i].last_sect -
434 req->seg[i].first_sect + 1;
435
436 if ((req->seg[i].last_sect >= (PAGE_SIZE >>
9)) ||
437 (req->seg[i].last_sect <
req->seg[i].first_sect))
438 goto fail_response;
...
L436 check whether the number of sectors in a segment of the I/O request exceeds
(PAGE_SIZE >> 9), which is 8 in x86, does that means vbd blkback driver
would not handle I/O request larger than 4k, I''m a newbie to Xen, so
would someone kindly explain the reason behind this, thanks.
Best Regards.
Han
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