Re: [Xen-devel] [PATCH v2 03/10] libx86: Introduce x86_cpu_policies_are_compatible()

[Andrew Cooper <andrew.cooper3@citrix.com>]

On 16/09/2019 11:59, Jan Beulich wrote:
> On 13.09.2019 21:27, Andrew Cooper wrote:
>> --- /dev/null
>> +++ b/xen/lib/x86/policy.c
>> @@ -0,0 +1,54 @@
>> +#include "private.h"
>> +
>> +#include <xen/lib/x86/cpu-policy.h>
>> +
>> +int x86_cpu_policies_are_compatible(const struct cpu_policy *host,
>> +                                    const struct cpu_policy *guest,
>> +                                    struct cpu_policy_errors *err)
>> +{
>> +    struct cpu_policy_errors e = INIT_CPU_POLICY_ERRORS;
>> +    int ret = -EINVAL;
>> +
>> +    if ( err )
>> +        *err = e;
> You don't really need this, do you? All paths lead ...
>
>> +#define NA XEN_CPUID_NO_SUBLEAF
>> +#define FAIL_CPUID(l, s) \
>> +    do { e.leaf = (l); e.subleaf = (s); goto out; } while ( 0 )
>> +#define FAIL_MSR(m) \
>> +    do { e.msr = (m); goto out; } while ( 0 )
>> +
>> +    if ( guest->cpuid->basic.max_leaf > host->cpuid->basic.max_leaf )
>> +        FAIL_CPUID(0, NA);
>> +
>> +    if ( guest->cpuid->extd.max_leaf > host->cpuid->extd.max_leaf )
>> +        FAIL_CPUID(0x80000008, NA);
>> +
>> +    /* TODO: Audit more CPUID data. */
>> +
>> +    if ( ~host->msr->platform_info.raw & guest->msr->platform_info.raw )
>> +        FAIL_MSR(MSR_INTEL_PLATFORM_INFO);
>> +
>> +#undef FAIL_MSR
>> +#undef FAIL_CPUID
>> +#undef NA
>> +
>> +    /* Success. */
>> +    ret = 0;
>> +
>> + out:
>> +    if ( ret && err )
>> +        *err = e;
> ... here, and hence you could simply drop the "ret &&" part of the
> condition.

Hmm - so they do.  I'll adjust as you suggest.

~Andrew

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