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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;
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