* [Qemu-devel] [PATCH v2] ppc: Force CPU threads count to be a power of 2.
@ 2014-03-05 8:32 Bharata B Rao
2014-03-05 13:59 ` Eric Blake
2014-03-05 22:51 ` Stewart Smith
0 siblings, 2 replies; 5+ messages in thread
From: Bharata B Rao @ 2014-03-05 8:32 UTC (permalink / raw)
To: qemu-devel; +Cc: aik, stewart, agraf, Bharata B Rao
PowerPC kernel expects the number of SMT threads in a core to be a power
of 2. Since QEMU doesn't enforce this, it leads to an early guest kernel
crash if invalid threads count is specified.
Prevent this crash and make it a graceful exit from QEMU itself by
validating the user supplied threads count.
Signed-off-by: Bharata B Rao <bharata@linux.vnet.ibm.com>
---
Changes in v2: Use is_power_of_2() from QEMU itself instead of depending
on libm.
v1: https://lists.gnu.org/archive/html/qemu-devel/2014-03/msg00660.html
v0: https://lists.gnu.org/archive/html/qemu-devel/2014-03/msg00355.html
target-ppc/translate_init.c | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/target-ppc/translate_init.c b/target-ppc/translate_init.c
index 445c360..5628248 100644
--- a/target-ppc/translate_init.c
+++ b/target-ppc/translate_init.c
@@ -7987,6 +7987,12 @@ static void ppc_cpu_realizefn(DeviceState *dev, Error **errp)
max_smt, kvm_enabled() ? "KVM" : "TCG");
return;
}
+ if (!is_power_of_2(smp_threads)) {
+ error_setg(errp, "Cannot support %d threads on PPC with %s, "
+ "threads count must be a power of 2.",
+ smp_threads, kvm_enabled() ? "KVM" : "TCG");
+ return;
+ }
#endif
if (kvm_enabled()) {
--
1.7.11.7
^ permalink raw reply related [flat|nested] 5+ messages in thread
* Re: [Qemu-devel] [PATCH v2] ppc: Force CPU threads count to be a power of 2.
2014-03-05 8:32 [Qemu-devel] [PATCH v2] ppc: Force CPU threads count to be a power of 2 Bharata B Rao
@ 2014-03-05 13:59 ` Eric Blake
2014-03-19 2:47 ` Bharata B Rao
2014-03-05 22:51 ` Stewart Smith
1 sibling, 1 reply; 5+ messages in thread
From: Eric Blake @ 2014-03-05 13:59 UTC (permalink / raw)
To: Bharata B Rao, qemu-devel; +Cc: aik, stewart, agraf
[-- Attachment #1: Type: text/plain, Size: 835 bytes --]
On 03/05/2014 01:32 AM, Bharata B Rao wrote:
> PowerPC kernel expects the number of SMT threads in a core to be a power
> of 2. Since QEMU doesn't enforce this, it leads to an early guest kernel
> crash if invalid threads count is specified.
>
> Prevent this crash and make it a graceful exit from QEMU itself by
> validating the user supplied threads count.
>
> Signed-off-by: Bharata B Rao <bharata@linux.vnet.ibm.com>
> ---
> Changes in v2: Use is_power_of_2() from QEMU itself instead of depending
> on libm.
> v1: https://lists.gnu.org/archive/html/qemu-devel/2014-03/msg00660.html
> v0: https://lists.gnu.org/archive/html/qemu-devel/2014-03/msg00355.html
Reviewed-by: Eric Blake <eblake@redhat.com>
--
Eric Blake eblake redhat com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
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^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [Qemu-devel] [PATCH v2] ppc: Force CPU threads count to be a power of 2.
2014-03-05 8:32 [Qemu-devel] [PATCH v2] ppc: Force CPU threads count to be a power of 2 Bharata B Rao
2014-03-05 13:59 ` Eric Blake
@ 2014-03-05 22:51 ` Stewart Smith
1 sibling, 0 replies; 5+ messages in thread
From: Stewart Smith @ 2014-03-05 22:51 UTC (permalink / raw)
To: Bharata B Rao, qemu-devel; +Cc: aik, agraf
Bharata B Rao <bharata@linux.vnet.ibm.com> writes:
> PowerPC kernel expects the number of SMT threads in a core to be a power
> of 2. Since QEMU doesn't enforce this, it leads to an early guest kernel
> crash if invalid threads count is specified.
>
> Prevent this crash and make it a graceful exit from QEMU itself by
> validating the user supplied threads count.
>
> Signed-off-by: Bharata B Rao <bharata@linux.vnet.ibm.com>
Reviewed-by: Stewart Smith <stewart@linux.vnet.ibm.com>
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [Qemu-devel] [PATCH v2] ppc: Force CPU threads count to be a power of 2.
2014-03-05 13:59 ` Eric Blake
@ 2014-03-19 2:47 ` Bharata B Rao
2014-03-19 22:58 ` Andreas Färber
0 siblings, 1 reply; 5+ messages in thread
From: Bharata B Rao @ 2014-03-19 2:47 UTC (permalink / raw)
To: Eric Blake; +Cc: aik, stewart, qemu-devel, Andreas Färber, agraf
On Wed, Mar 05, 2014 at 06:59:29AM -0700, Eric Blake wrote:
> On 03/05/2014 01:32 AM, Bharata B Rao wrote:
> > PowerPC kernel expects the number of SMT threads in a core to be a power
> > of 2. Since QEMU doesn't enforce this, it leads to an early guest kernel
> > crash if invalid threads count is specified.
> >
> > Prevent this crash and make it a graceful exit from QEMU itself by
> > validating the user supplied threads count.
> >
> > Signed-off-by: Bharata B Rao <bharata@linux.vnet.ibm.com>
> > ---
> > Changes in v2: Use is_power_of_2() from QEMU itself instead of depending
> > on libm.
> > v1: https://lists.gnu.org/archive/html/qemu-devel/2014-03/msg00660.html
> > v0: https://lists.gnu.org/archive/html/qemu-devel/2014-03/msg00355.html
>
> Reviewed-by: Eric Blake <eblake@redhat.com>
> Reviewed-by: Stewart Smith <stewart@linux.vnet.ibm.com>
Alexander/Andreas,
Could you take this patch into your tree ?
Regards,
Bharata.
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [Qemu-devel] [PATCH v2] ppc: Force CPU threads count to be a power of 2.
2014-03-19 2:47 ` Bharata B Rao
@ 2014-03-19 22:58 ` Andreas Färber
0 siblings, 0 replies; 5+ messages in thread
From: Andreas Färber @ 2014-03-19 22:58 UTC (permalink / raw)
To: bharata; +Cc: aik, stewart, qemu-devel, agraf
Am 19.03.2014 03:47, schrieb Bharata B Rao:
> On Wed, Mar 05, 2014 at 06:59:29AM -0700, Eric Blake wrote:
>> On 03/05/2014 01:32 AM, Bharata B Rao wrote:
>>> PowerPC kernel expects the number of SMT threads in a core to be a power
>>> of 2. Since QEMU doesn't enforce this, it leads to an early guest kernel
>>> crash if invalid threads count is specified.
>>>
>>> Prevent this crash and make it a graceful exit from QEMU itself by
>>> validating the user supplied threads count.
>>>
>>> Signed-off-by: Bharata B Rao <bharata@linux.vnet.ibm.com>
>>> ---
>>> Changes in v2: Use is_power_of_2() from QEMU itself instead of depending
>>> on libm.
>>> v1: https://lists.gnu.org/archive/html/qemu-devel/2014-03/msg00660.html
>>> v0: https://lists.gnu.org/archive/html/qemu-devel/2014-03/msg00355.html
>>
>> Reviewed-by: Eric Blake <eblake@redhat.com>
>
>> Reviewed-by: Stewart Smith <stewart@linux.vnet.ibm.com>
>
> Alexander/Andreas,
>
> Could you take this patch into your tree ?
Thanks for the reminder.
Didn't apply cleanly any more. Applied to my ppc-next with fixups:
https://github.com/afaerber/qemu-cpu/commits/ppc-next
Andreas
diff --cc target-ppc/translate_init.c
index 3269c3e,5628248..0000000
--- a/target-ppc/translate_init.c
+++ b/target-ppc/translate_init.c
@@@ -7848,12 -7987,20 +7848,18 @@@ static void ppc_cpu_realizefn(DeviceSta
max_smt, kvm_enabled() ? "KVM" : "TCG");
return;
}
+ if (!is_power_of_2(smp_threads)) {
+ error_setg(errp, "Cannot support %d threads on PPC with %s, "
+ "threads count must be a power of 2.",
+ smp_threads, kvm_enabled() ? "KVM" : "TCG");
+ return;
+ }
+
+ cpu->cpu_dt_id = (cs->cpu_index / smp_threads) * max_smt
+ + (cs->cpu_index % smp_threads);
#endif
- if (kvm_enabled()) {
- if (kvmppc_fixup_cpu(cpu) != 0) {
- error_setg(errp, "Unable to virtualize selected CPU with
KVM");
- return;
- }
- } else if (tcg_enabled()) {
+ if (tcg_enabled()) {
if (ppc_fixup_cpu(cpu) != 0) {
error_setg(errp, "Unable to emulate selected CPU with TCG");
return;
--
SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg, Germany
GF: Jeff Hawn, Jennifer Guild, Felix Imendörffer; HRB 16746 AG Nürnberg
^ permalink raw reply [flat|nested] 5+ messages in thread
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2014-03-05 8:32 [Qemu-devel] [PATCH v2] ppc: Force CPU threads count to be a power of 2 Bharata B Rao
2014-03-05 13:59 ` Eric Blake
2014-03-19 2:47 ` Bharata B Rao
2014-03-19 22:58 ` Andreas Färber
2014-03-05 22:51 ` Stewart Smith
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