Subject: Re: [PATCH] powerpc/kvmbook3s_hv: propagate H_SET_MODE to the host

From: Laurent Dufour <[email-masked]>
Date: Fri, 27 Sep 2013 10:14:15 +0200

On 26/09/2013 00:31, Paul Mackerras wrote:
> On Wed, Sep 25, 2013 at 02:10:27PM +0200, Laurent Dufour wrote:
>> Follow-up to Anton's H_SET_MODE patch, the host should be taken aware of
>> guest endianess change.
>>
>> The hcall H_SET_MODE is processed in kvm then in the host.
>>
>> Signed-off-by: Laurent Dufour <[email-masked]>
>> ---
>>  arch/powerpc/kvm/book3s_hv.c |    8 ++++++++
>>  1 file changed, 8 insertions(+)
>>
>> diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c
>> index 998cad3..4a47c74 100644
>> --- a/arch/powerpc/kvm/book3s_hv.c
>> +++ b/arch/powerpc/kvm/book3s_hv.c
>> @@ -599,6 +599,14 @@ int kvmppc_pseries_do_hcall(struct kvm_vcpu *vcpu)
>>  					kvmppc_get_gpr(vcpu, 5),
>>  					kvmppc_get_gpr(vcpu, 6),
>>  					kvmppc_get_gpr(vcpu, 7));
>> +		/*
>> +		 * If the hcall succeeded, we propagate it to the host.
>> +		 * This way, it will be aware of the endianess's change too.
>> +		 * The assumption is made that the hcall will succeed in the
>> +		 * host.
>> +		 */
>> +		if (ret == H_SUCCESS)
>> +			return RESUME_HOST;
>>  		break;
> 
> The problem with this is that H_SET_MODE isn't just used for setting
> endianness; it also does breakpoint setting (DAWR/X and CIABR), which
> might happen very frequently, so we don't want them being punted up to
> userspace.
> 
> Paul.

Hi Paul,

My mistake, the patch was based on a too old kernel missing yours and
Michael's latest patches on H_SET_MODE handling.

I'll propose a new one asap.

Thanks,
Laurent.