Hello,
After upgrading host kernel to 6.0 QEMU 7.0.0 guests can't boot if their
underlying disk image has 4096 byte sectors and cache property set to
"none".
Host kernel:
Linux version 6.0.2 (root@xxxxxxxxxxxxxx) (gcc (Gentoo 11.3.0 p4)
11.3.0, GNU ld (Gentoo 2.38 p4) 2.38) #1 SMP
Bisect led me to commit b1a000d3b8ec5 ("block: relax direct io memory
alignment"). I was unable to resolve revert conflicts when
tried to revert b1a000d3b8ec5 ("block: relax direct io memory
alignment") as I lack necessary understanding of block subsystem.
This fails to boot on 6.0+ host:
# losetup -b 4096 -f image.raw
# qemu-system-x86_64 -enable-kvm -drive
file=/dev/loop0,format=raw,cache=none
These boot fine on 6.0+ host:
# losetup -b 4096 -f image.raw
# qemu-system-x86_64 -enable-kvm -drive
file=/dev/loop0,format=raw
# losetup -f image.raw
# qemu-system-x86_64 -enable-kvm -drive
file=/dev/loop0,format=raw,cache=none
On 5.19 and older kernels the guest boots in all cases above. Problem
reproduces on 6.1-rc1.
What other info I can provide to help to find root cause?
Bisect log:
git bisect start
# status: waiting for both good and bad commits
# bad: [4fe89d07dcc2804c8b562f6c7896a45643d34b2f] Linux 6.0
git bisect bad 4fe89d07dcc2804c8b562f6c7896a45643d34b2f
# status: waiting for good commit(s), bad commit known
# good: [3d7cb6b04c3f3115719235cc6866b10326de34cd] Linux 5.19
git bisect good 3d7cb6b04c3f3115719235cc6866b10326de34cd
# bad: [78acd4ca433425e6dd4032cfc2156c60e34931f2] usb: cdns3: Don't use priv_dev uninitialized in cdns3_gadget_ep_enable()
git bisect bad 78acd4ca433425e6dd4032cfc2156c60e34931f2
# bad: [526942b8134cc34d25d27f95dfff98b8ce2f6fcd] Merge tag 'ata-5.20-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/dlemoal/libata
git bisect bad 526942b8134cc34d25d27f95dfff98b8ce2f6fcd
# good: [2e7a95156d64667a8ded606829d57c6fc92e41df] Merge tag 'regmap-v5.20' of git://git.kernel.org/pub/scm/linux/kernel/git/broonie/regmap
git bisect good 2e7a95156d64667a8ded606829d57c6fc92e41df
# bad: [c013d0af81f60cc7dbe357c4e2a925fb6738dbfe] Merge tag 'for-5.20/block-2022-07-29' of git://git.kernel.dk/linux-block
git bisect bad c013d0af81f60cc7dbe357c4e2a925fb6738dbfe
# good: [efb2883060afc79638bb1eb19e2c30e7f6c5a178] Merge branch 'turbostat' of git://git.kernel.org/pub/scm/linux/kernel/git/lenb/linux
git bisect good efb2883060afc79638bb1eb19e2c30e7f6c5a178
# good: [cb309ae49da7a7c28f0051deea13970291134fac] io_uring/net: improve io_get_notif_slot types
git bisect good cb309ae49da7a7c28f0051deea13970291134fac
# bad: [22c80aac882f712897b88b7ea8f5a74ea19019df] blktrace: Trace remapped requests correctly
git bisect bad 22c80aac882f712897b88b7ea8f5a74ea19019df
# bad: [22d0c4080fe49299640d9d6c43154c49794c2825] block: simplify disk_set_independent_access_ranges
git bisect bad 22d0c4080fe49299640d9d6c43154c49794c2825
# bad: [3c8f9da41ed90294d8ca42b3ad8a13c5379bd549] blk-mq: Don't disable preemption around __blk_mq_run_hw_queue().
git bisect bad 3c8f9da41ed90294d8ca42b3ad8a13c5379bd549
# bad: [798f2a6f734de87633351c3ab13b17b07397cf68] block: Directly use ida_alloc()/free()
git bisect bad 798f2a6f734de87633351c3ab13b17b07397cf68
# good: [67927d22015060967122facc8cfeaad8012e8808] block/merge: count bytes instead of sectors
git bisect good 67927d22015060967122facc8cfeaad8012e8808
# good: [5debd9691c3ac64c3acd6867c264ad38bbe48cdc] block: introduce bdev_iter_is_aligned helper
git bisect good 5debd9691c3ac64c3acd6867c264ad38bbe48cdc
# bad: [bf8d08532bc19a14cfb54ae61099dccadefca446] iomap: add support for dma aligned direct-io
git bisect bad bf8d08532bc19a14cfb54ae61099dccadefca446
# bad: [b1a000d3b8ec582da64bb644be633e5a0beffcbf] block: relax direct io memory alignment
git bisect bad b1a000d3b8ec582da64bb644be633e5a0beffcbf
# first bad commit: [b1a000d3b8ec582da64bb644be633e5a0beffcbf] block: relax direct io memory alignment
