Bug 260200
| Summary: | AHCI emulation throws CAM errors when backed by -t malloc memory disk devices | ||
|---|---|---|---|
| Product: | Base System | Reporter: | Michael Dexter <editor> |
| Component: | bhyve | Assignee: | freebsd-virtualization (Nobody) <virtualization> |
| Status: | Open --- | ||
| Severity: | Affects Only Me | CC: | afedorov, markj |
| Priority: | --- | ||
| Version: | 13.0-RELEASE | ||
| Hardware: | Any | ||
| OS: | Any | ||
|
Description
Michael Dexter
2021-12-04 06:10:44 UTC
Update: bhyve/illumos does not exhibit this issue under similar testing with ramdiskadm(M1) devices. This is because md(4) + memory backend doesn't support the DIOCGFLUSH ioctl (BIO_FLUSH command): https://github.com/freebsd/freebsd-src/blob/main/sys/dev/md/md.c#L650 pci_ahci.c: https://github.com/freebsd/freebsd-src/blob/main/usr.sbin/bhyve/pci_ahci.c#L783 So I see two ways to solve this issue. First, fix bhyve with patch like this: diff --git a/usr.sbin/bhyve/block_if.c b/usr.sbin/bhyve/block_if.c index 98c0f9f5f38b..3fb81bb86ae2 100644 --- a/usr.sbin/bhyve/block_if.c +++ b/usr.sbin/bhyve/block_if.c @@ -102,6 +102,7 @@ struct blockif_ctxt { int bc_ischr; int bc_isgeom; int bc_candelete; + int bc_canflush; int bc_rdonly; off_t bc_size; int bc_sectsz; @@ -224,6 +225,8 @@ static int blockif_flush_bc(struct blockif_ctxt *bc) { if (bc->bc_ischr) { + if (bc->bc_canflush == 0) + return (0); if (ioctl(bc->bc_fd, DIOCGFLUSH)) return (errno); } else if (fsync(bc->bc_fd)) @@ -463,7 +466,7 @@ blockif_open(nvlist_t *nvl, const char *ident) struct diocgattr_arg arg; off_t size, psectsz, psectoff; int extra, fd, i, sectsz; - int ro, candelete, geom, ssopt, pssopt; + int ro, candelete, canflush, geom, ssopt, pssopt; int nodelete; #ifndef WITHOUT_CAPSICUM @@ -566,6 +569,12 @@ blockif_open(nvlist_t *nvl, const char *ident) candelete = arg.value.i; if (ioctl(fd, DIOCGPROVIDERNAME, name) == 0) geom = 1; + if (ioctl(fd, DIOCGFLUSH) == 0) + canflush = 1; + else if (errno == ENOTSUP) { + canflush = 0; + errno = 0; + } } else psectsz = sbuf.st_blksize; @@ -614,6 +623,7 @@ blockif_open(nvlist_t *nvl, const char *ident) bc->bc_ischr = S_ISCHR(sbuf.st_mode); bc->bc_isgeom = geom; bc->bc_candelete = candelete; + bc->bc_canflush = canflush; bc->bc_rdonly = ro; bc->bc_size = size; bc->bc_sectsz = sectsz; Second, add a NOP support of the BIO_FLUSH cmd to md(4) (mdstart_malloc()). Second way:
diff --git a/sys/dev/md/md.c b/sys/dev/md/md.c
index 308374f49f14..affb0780fa4a 100644
--- a/sys/dev/md/md.c
+++ b/sys/dev/md/md.c
@@ -643,6 +643,9 @@ mdstart_malloc(struct md_s *sc, struct bio *bp)
case BIO_WRITE:
case BIO_DELETE:
break;
+ case BIO_FLUSH:
+ bp->bio_resid = 0;
+ return (0);
default:
return (EOPNOTSUPP);
}
(In reply to Aleksandr Fedorov from comment #3) I'd be tempted to change md(4) to simply ignore BIO_FLUSH in malloc-backed MDs, rather than adding complexity to bhyve. The second patch looks ok to me. Should swap-backed MDs also be changed? What effect should BIO_FLUSH have there? Thank you for looking into this. I confirmed that this behavior is with both malloc and swap memory devices, but is not present with CTL "ramdisk" devices. i.e.: mdconfig -s 256m -t malloc -u 11 mdconfig -s 256m -t swap -u 12 ctladm create -b ramdisk -s 256m -o capacity=256m ctladm port -o on <pass to VM, run fio against them> I think the swap backend should also ignore the BIO_FLUSH command. Because swap is not a persistent storage, I don't know how BIO_FLUSH can be useful. As for ctl(4), it works with SCSI commands. Ramdisk backend simply ignores the SYNCHRONIZE_CACHE and SYNCHRONIZE_CACHE_16 commands: https://github.com/freebsd/freebsd-src/blob/main/sys/cam/ctl/ctl_backend_ramdisk.c#L748 This review applies cleanly against 13.0R and passes my dd(1) and fio(1) tests. Thank you! A commit in branch main references this bug: URL: https://cgit.FreeBSD.org/src/commit/?id=cb28dfb27d12f1cbd7831f370c01493c01d74b10 commit cb28dfb27d12f1cbd7831f370c01493c01d74b10 Author: Aleksandr Fedorov <afedorov@FreeBSD.org> AuthorDate: 2022-02-17 19:21:56 +0000 Commit: Aleksandr Fedorov <afedorov@FreeBSD.org> CommitDate: 2022-02-17 19:21:56 +0000 md(4): Add dummy support of the BIO_FLUSH command for malloc and swap backend. PR: 260200 Reported by: editor@callfortesting.org Reviewed by: vmaffione (mentor), markj Approved by: vmaffione (mentor), markj Differential Revision: https://reviews.freebsd.org/D34260 sys/dev/md/md.c | 4 ++++ 1 file changed, 4 insertions(+) A commit in branch stable/13 references this bug: URL: https://cgit.FreeBSD.org/src/commit/?id=f40063d329775a7c7bdac90afd261b683ad2fec3 commit f40063d329775a7c7bdac90afd261b683ad2fec3 Author: Aleksandr Fedorov <afedorov@FreeBSD.org> AuthorDate: 2022-02-17 19:21:56 +0000 Commit: Aleksandr Fedorov <afedorov@FreeBSD.org> CommitDate: 2022-02-23 10:57:44 +0000 md(4): Add dummy support of the BIO_FLUSH command for malloc and swap backend. PR: 260200 Reported by: editor@callfortesting.org Reviewed by: vmaffione (mentor), markj Approved by: vmaffione (mentor), markj Differential Revision: https://reviews.freebsd.org/D34260 (cherry picked from commit cb28dfb27d12f1cbd7831f370c01493c01d74b10) sys/dev/md/md.c | 4 ++++ 1 file changed, 4 insertions(+) |
