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Re: [Qemu-ppc] KVM-PR is broken with current QEMU
From: |
Cédric Le Goater |
Subject: |
Re: [Qemu-ppc] KVM-PR is broken with current QEMU |
Date: |
Tue, 20 Sep 2016 16:04:43 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.3.0 |
On 09/20/2016 02:24 PM, Cédric Le Goater wrote:
> On 09/20/2016 01:44 PM, Thomas Huth wrote:
>> Hi,
>>
>> when I try to run my guest in KVM-PR mode, current QEMU refuses to start:
>>
>> $ sudo qemu-system-ppc64 -M pseries,accel=kvm,kvm-type=PR \
>> -nographic -vga none -cpu POWER8
>> qemu: fatal: Unknown MMU model 851972
>>
>> ... followed by a useless register dump. I've bisected the issue, and it
>> seems like the problem has been introduced by this commit here:
>>
>> commit 4322e8ced5aaac7191958f09622d199fe61e2d87
>> ppc: Fix 64K pages support in full emulation
>>
>> Seems like KVM PR is using the "degraded" ISA variants (without the 1TB
>> segments), but the new POWERPC_MMU_64K flag has not been added to those.
>> Has this been done on purpose, or was this just by accident?
>
> The "degraded" architecture support has some history behind it :
>
> commit 126a79300971 added it
> commit aa4bb5875231 removed it.
> commit ba3ecda05e93 readded it.
> commit 4322e8ced5aa forgot about it again
>
>> I can make KVM PR working again with the following patch:
>
> I think this is correct. Let's wait for Ben to chime in :)
So I confirm the bug and the fix.
There are other issues after in the guest (kernel crashing). But I think
these are related to TM which is not supported in KVM-PR. I am not sure
where we are on that point.
Thanks,
C.
>> diff --git a/target-ppc/cpu-qom.h b/target-ppc/cpu-qom.h
>> index 2864105..36694cb 100644
>> --- a/target-ppc/cpu-qom.h
>> +++ b/target-ppc/cpu-qom.h
>> @@ -81,6 +81,7 @@ enum powerpc_mmu_t {
>> | POWERPC_MMU_AMR | 0x00000003,
>> /* Architecture 2.06 "degraded" (no 1T segments) */
>> POWERPC_MMU_2_06a = POWERPC_MMU_64 | POWERPC_MMU_AMR
>> + | POWERPC_MMU_64K
>> | 0x00000003,
>> /* Architecture 2.07 variant */
>> POWERPC_MMU_2_07 = POWERPC_MMU_64 | POWERPC_MMU_1TSEG
>> @@ -88,6 +89,7 @@ enum powerpc_mmu_t {
>> | POWERPC_MMU_AMR | 0x00000004,
>> /* Architecture 2.07 "degraded" (no 1T segments) */
>> POWERPC_MMU_2_07a = POWERPC_MMU_64 | POWERPC_MMU_AMR
>> + | POWERPC_MMU_64K
>> | 0x00000004,
>> };
>>
>> However, not sure whether this is the right fix ... Cédric, Ben, any ideas?
>
>
>
>
- [Qemu-ppc] KVM-PR is broken with current QEMU, Thomas Huth, 2016/09/20
- Re: [Qemu-ppc] KVM-PR is broken with current QEMU, Cédric Le Goater, 2016/09/20
- Re: [Qemu-ppc] KVM-PR is broken with current QEMU,
Cédric Le Goater <=
- Re: [Qemu-ppc] KVM-PR is broken with current QEMU, Thomas Huth, 2016/09/20
- Re: [Qemu-ppc] KVM-PR is broken with current QEMU, Cédric Le Goater, 2016/09/20
- Re: [Qemu-ppc] KVM-PR is broken with current QEMU, Thomas Huth, 2016/09/21
- Re: [Qemu-ppc] KVM-PR is broken with current QEMU, David Gibson, 2016/09/22
- Re: [Qemu-ppc] [Qemu-devel] KVM-PR is broken with current QEMU, Thomas Huth, 2016/09/22
- Re: [Qemu-ppc] [Qemu-devel] KVM-PR is broken with current QEMU, Thomas Huth, 2016/09/22
- Re: [Qemu-ppc] [Qemu-devel] KVM-PR is broken with current QEMU, Cédric Le Goater, 2016/09/22
- Re: [Qemu-ppc] [Qemu-devel] KVM-PR is broken with current QEMU, Anton Blanchard, 2016/09/22
Re: [Qemu-ppc] KVM-PR is broken with current QEMU, Benjamin Herrenschmidt, 2016/09/20