On Mon, Nov 09, 2015 at 03:24:15PM +1100, David Gibson wrote: > On Tue, Nov 03, 2015 at 03:38:19PM +0530, Bharata B Rao wrote: > > 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 <bhar...@linux.vnet.ibm.com> > > I'm going to apply this, since it fixes a real problem. > > I'm not entirely happy with the way it's done though - I'd prefer to > see a separate case for (shift < 0) giving an unconditional error. > Handling both the HV success case and the failure case in that first > branch is unnecessarily subtle and confusing, IMO.
Ugh.. actually.. this patch seems to cause make check failures when configured for powerpc guest on an x86 host. I haven't debugged yet, but I'm guessing the shift != 0 is now catching the TCG (or PR) case where we need to allocate the htab ourselves. > > > > --- > > hw/ppc/spapr.c | 4 ++-- > > 1 file changed, 2 insertions(+), 2 deletions(-) > > > > diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c > > index e1202ce..ec6e141 100644 > > --- a/hw/ppc/spapr.c > > +++ b/hw/ppc/spapr.c > > @@ -1022,7 +1022,7 @@ static void spapr_alloc_htab(sPAPRMachineState *spapr) > > > > shift = kvmppc_reset_htab(spapr->htab_shift); > > > > - if (shift > 0) { > > + if (shift != 0) { > > /* Kernel handles htab, we don't need to allocate one */ > > if (shift != spapr->htab_shift) { > > error_setg(&error_abort, "Failed to allocate HTAB of requested > > size, try with smaller maxmem"); > > @@ -1055,7 +1055,7 @@ static void spapr_reset_htab(sPAPRMachineState *spapr) > > int index; > > > > shift = kvmppc_reset_htab(spapr->htab_shift); > > - if (shift > 0) { > > + if (shift != 0) { > > if (shift != spapr->htab_shift) { > > error_setg(&error_abort, "Requested HTAB allocation failed > > during reset"); > > } > -- 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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