On 29.08.2013, at 07:04, Paul Mackerras wrote:
> On Thu, Aug 29, 2013 at 12:00:53AM +0200, Alexander Graf wrote:
>>
>> On 06.08.2013, at 06:16, Paul Mackerras wrote:
>>
>>> kvm_start_lightweight:
>>> + /* Copy registers into shadow vcpu so we can access them in real mode */
>>> + GET_SHADOW_VCPU(r3)
>>> + bl FUNC(kvmppc_copy_to_svcpu)
>>
>> This will clobber r3 and r4, no? We need to restore them from the stack here
>> I would think.
>
> You're right. We don't need to restore r3 since we don't actually use
> it, but we do need to restore r4.
>
>>> #ifdef CONFIG_PPC_BOOK3S_32
>>> /* We set segments as unused segments when invalidating them. So
>>> * treat the respective fault as segment fault. */
>>> - if (svcpu->sr[kvmppc_get_pc(vcpu) >> SID_SHIFT] == SR_INVALID) {
>>> - kvmppc_mmu_map_segment(vcpu, kvmppc_get_pc(vcpu));
>>> - r = RESUME_GUEST;
>>> + {
>>> + struct kvmppc_book3s_shadow_vcpu *svcpu;
>>> + u32 sr;
>>> +
>>> + svcpu = svcpu_get(vcpu);
>>> + sr = svcpu->sr[kvmppc_get_pc(vcpu) >> SID_SHIFT];
>>
>> Doesn't this break two concurrently running guests now that we don't copy
>> the shadow vcpu anymore? Just move the sr array to a kmalloc'ed area until
>> the whole vcpu is kmalloc'ed. Then you can get rid of all shadow vcpu code.
>
> This is 32-bit only... the svcpu is already kmalloc'ed, so I'm not
> sure what you're asking for here or why you think this would break
> with multiple guests.
Oh, you're right. It wouldn't. I was confused and thought that svcpu_get()
would give you the in-paca view, but on 32bit we already keep it as separate
kmalloc'ed area.
Alex
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