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Re: [Qemu-devel] [PATCH v1 2/2] spapr: Handle failure of KVM_PPC_ALLOCAT
From: |
David Gibson |
Subject: |
Re: [Qemu-devel] [PATCH v1 2/2] spapr: Handle failure of KVM_PPC_ALLOCATE_HTAB ioctl |
Date: |
Wed, 11 Nov 2015 11:07:52 +1100 |
User-agent: |
Mutt/1.5.23 (2015-06-09) |
On Tue, Nov 10, 2015 at 08:38:57AM -0600, Michael Roth wrote:
> Quoting Bharata B Rao (2015-11-09 23:24:54)
> > KVM_PPC_ALLOCATE_HTAB ioctl can return -ENOMEM for KVM guests and QEMU
> > never handled this correctly. But this didn't cause any problems till
> > now as KVM_PPC_ALLOCATE_HTAB ioctl returned with smaller than requested
> > HTAB when enough contiguous memory wasn't available in the host.
> > After the proposed kernel change:
> > https://patchwork.ozlabs.org/patch/530501/,
> > KVM_PPC_ALLOCATE_HTAB ioctl will not fallback to lower sized HTAB
> > allocation and will fail if requested HTAB size can't be met.
> >
> > Check for such failures in QEMU and abort appropriately. This will
> > prevent guest kernel from hanging/freezing during early boot by doing
> > graceful exit when host is unable to allocate requested HTAB.
> >
> > Signed-off-by: Bharata B Rao <address@hidden>
> > ---
> > hw/ppc/spapr.c | 20 ++++++++++++++++----
> > 1 file changed, 16 insertions(+), 4 deletions(-)
> >
> > diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> > index e1202ce..a64a1b5 100644
> > --- a/hw/ppc/spapr.c
> > +++ b/hw/ppc/spapr.c
> > @@ -1021,9 +1021,19 @@ static void spapr_alloc_htab(sPAPRMachineState
> > *spapr)
> > * RAM */
> >
> > shift = kvmppc_reset_htab(spapr->htab_shift);
> > -
> > - if (shift > 0) {
> > - /* Kernel handles htab, we don't need to allocate one */
> > + if (shift < 0) {
> > + /*
> > + * For HV KVM, host kernel will return -ENOMEM when requested
> > + * HTAB size can't be allocated.
> > + */
> > + error_setg(&error_abort, "Failed to allocate HTAB of requested
> > size, try with smaller maxmem");
>
> Wording is appropriate, but maybe just "Failed to allocate HTAB, try with
> smaller maxmem" to distinguish it from the error below where the call succeeds
> but there's a size mismatch?
Possibly the message could be a little better, but I'm not going to
hold up the patches just for that. I've applied tentatively to
spapr-next, and I hope to send a pull req with it soon, assuming it
survives my tests.
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
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