Re: [PATCH v2 1/5] x86/hvm: Handle viridian MSRs via the new guest_{rd, wr}msr() infrastructure

From: Andrew Cooper <andrew.cooper3@citrix.com>
To: Jan Beulich <JBeulich@suse.com>
Cc: Sergey Dyasli <sergey.dyasli@citrix.com>,
	Wei Liu <wei.liu2@citrix.com>,
	Xen-devel <xen-devel@lists.xen.org>
Subject: Re: [PATCH v2 1/5] x86/hvm: Handle viridian MSRs via the new guest_{rd, wr}msr() infrastructure
Date: Tue, 13 Mar 2018 15:47:40 +0000	[thread overview]
Message-ID: <41c1d046-117c-c9c7-077e-42ae6ef90656@citrix.com> (raw)
In-Reply-To: <5AA7FA4A02000078001B10D9@prv-mh.provo.novell.com>

On 13/03/18 15:20, Jan Beulich wrote:
>>>> On 07.03.18 at 19:58, <andrew.cooper3@citrix.com> wrote:
>> @@ -175,11 +177,26 @@ int guest_rdmsr(const struct vcpu *v, uint32_t msr, uint64_t *val)
>>                 _MSR_MISC_FEATURES_CPUID_FAULTING;
>>          break;
>>  
>> +    case MSR_HYPERVISOR_START ... MSR_HYPERVISOR_START + NR_VIRIDIAN_MSRS - 
>> 1:
>> +        if ( is_viridian_domain(d) )
>> +        {
>> +            ret = guest_rdmsr_viridian(v, msr, val);
>> +            goto out;
>> +        }
>> +
>> +        /* Fallthrough. */
>>      default:
>>          return X86EMUL_UNHANDLEABLE;
>>      }
>>  
>> -    return X86EMUL_OKAY;
>> + out:
> I've noticed this only in the context of patch 4, but why is this label
> and yet another unnecessary "goto" here? That "goto" could simply
> be "break" afaics.

Ah - that is for changes which I haven't posted yet.

When we get onto MSRs which might be in the load/save lists, or may be
stashed in the VMCB/VMCS rather than in real hardware, we need to call
back into arch specific code when an update is completed.

~Andrew

_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xenproject.org
https://lists.xenproject.org/mailman/listinfo/xen-devel