Re: Linux PV/PVH domU crash on (guest) resume from suspend

[Jürgen Groß <jgross@xxxxxxxx>]

On 19.02.21 14:37, Jan Beulich wrote:
> On 19.02.2021 14:18, Jürgen Groß wrote:
> > On 19.02.21 14:10, Jan Beulich wrote:
> > > On 19.02.2021 13:48, Jürgen Groß wrote:
> > > > On 17.02.21 14:48, Marek Marczykowski-Górecki wrote:
> > > > > On Wed, Feb 17, 2021 at 07:51:42AM +0100, Jürgen Groß wrote:
> > > > > > On 17.02.21 06:12, Marek Marczykowski-Górecki wrote:
> > > > > > > Hi,
> > > > > > >
> > > > > > > I'm observing Linux PV/PVH guest crash when I resume it from sleep. I do
> > > > > > > this with:
> > > > > > >
> > > > > > >         virsh -c xen dompmsuspend <vmname> mem
> > > > > > >         virsh -c xen dompmwakeup <vmname>
> > > > > > >
> > > > > > > But it's possible to trigger it with plain xl too:
> > > > > > >
> > > > > > >         xl save -c <vmname> <some-file>
> > > > > > >
> > > > > > > The same on HVM works fine.
> > > > > > >
> > > > > > > This is on Xen 4.14.1, and with guest kernel 5.4.90, the same happens
> > > > > > > with 5.4.98. Dom0 kernel is the same, but I'm not sure if that's
> > > > > > > relevant here. I can reliably reproduce it.
> > > > > > This is already on my list of issues to look at.
> > > > > >
> > > > > > The problem seems to be related to the XSA-332 patches. You could try
> > > > > > the patches I've sent out recently addressing other fallout from XSA-332
> > > > > > which _might_ fix this issue, too:
> > > > > >
> > > > > > https://patchew.org/Xen/20210211101616.13788-1-jgross@xxxxxxxx/
> > > > > Thanks for the patches. Sadly it doesn't change anything - I get exactly
> > > > > the same crash. I applied that on top of 5.11-rc7 (that's what I had
> > > > > handy). If you think there may be a difference with the final 5.11 or
> > > > > another branch, please let me know.
> > > > Some more tests reveal that this seems to be s hypervisor regression.
> > > > I can reproduce the very same problem with a 4.12 kernel from 2019.
> > > >
> > > > It seems as if the EVTCHNOP_init_control hypercall is returning
> > > > -EINVAL when the domain is continuing to run after the suspend
> > > > hypercall (in contrast to the case where a new domain has been created
> > > > when doing a "xl restore").
> > > But when you resume the same domain, the kernel isn't supposed to
> > > call EVTCHNOP_init_control, as that's a one time operation (per
> > > vCPU, and unless EVTCHNOP_reset was called of course). In the
> > > hypervisor map_control_block() has (always had) as its first step
> > >
> > >       if ( v->evtchn_fifo->control_block )
> > >           return -EINVAL;
> > >
> > > Re-setup is needed only when resuming in a new domain.
> > But the same guest will not crash when doing the same on a 4.12
> > hypervisor.
> Is the kernel perhaps not given the bit of information anymore that
> it needs to tell apart the two resume modes?
Ah, yes, this might be the problem.

EVTCHNOP_init_control is indeed used only if the suspend hypercall did
return 0.


Juergen

Attachment: OpenPGP_0xB0DE9DD628BF132F.asc
Description: application/pgp-keys

Attachment: OpenPGP_signature
Description: OpenPGP digital signature