qemu-devel
[Top][All Lists]
Advanced

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [Qemu-devel] [PATCH v2] ppc: Force CPU threads count to be a power o


From: Andreas Färber
Subject: Re: [Qemu-devel] [PATCH v2] ppc: Force CPU threads count to be a power of 2.
Date: Wed, 19 Mar 2014 23:58:18 +0100
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.3.0

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 <address@hidden>
>>> ---
>>> 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 <address@hidden>
> 
>> Reviewed-by: Stewart Smith <address@hidden>
> 
> 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



reply via email to

[Prev in Thread] Current Thread [Next in Thread]