Re: [Qemu-devel] [Qemu-block] [PATCH] scsi-generic: prevent guest from exceeding SG_IO limits

[Kevin Wolf <kwolf@redhat.com>]

Am 18.04.2019 um 11:48 hat Paolo Bonzini geschrieben:
> On 17/04/19 14:30, Stefan Hajnoczi wrote:
> > On Wed, Apr 17, 2019 at 12:54 PM Paolo Bonzini <pbonzini@redhat.com> wrote:
> >> Linux places a limit of UIO_MAXIOV pages on SG_IO ioctls (and if the limit
> >> is exceeded, a confusing ENOMEM error is returned[1]).  Prevent the guest
> >> from exceeding these limits, by capping the maximum transfer length to
> >> that value in the block limits VPD page.
> >>
> >> [1] Oh well, at least it was easier to follow the kernel source knowing
> >>     it had to end as ENOMEM...
> >>
> >> Cc: qemu-stable@nongnu.org
> >> Cc: qemu-block@nongnu.org
> >> Cc: Stefan Hajnoczi <stefanha@redhat.com>
> >> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> >> ---
> >>  hw/scsi/scsi-generic.c | 17 +++++++++++++----
> >>  1 file changed, 13 insertions(+), 4 deletions(-)
> > 
> > Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
> > 
> 
> This is acually only an issue with kernels prior to 4.5, so it should be
> fixed downstream instead.

I don't think that upstream QEMU has kernels > 4.5 as an official
requirement, though? We try to be compatible with quite old libs, so we
should stay compatible with old kernels, too.

Kevin