On Mon, Dec 06, 2021 at 05:09:42PM +0100, Jan Beulich wrote:
> On 29.11.2021 16:33, Roger Pau Monne wrote:
> > @@ -458,22 +456,6 @@ int xc_cpuid_apply_policy(xc_interface *xch, uint32_t
> > domid, bool restore,
> > (p = calloc(1, sizeof(*p))) == NULL )
> > goto out;
> >
> > - /* Get the host policy. */
> > - rc = xc_get_cpu_featureset(xch, XEN_SYSCTL_cpu_featureset_host,
> > - &len, host_featureset);
>
> You go from retrieving the host featureset to ...
>
> > @@ -944,3 +865,98 @@ int xc_cpu_policy_make_compat_4_12(xc_interface *xch,
> > xc_cpu_policy_t *policy,
> > xc_cpu_policy_destroy(host);
> > return rc;
> > }
> > +
> > +int xc_cpu_policy_legacy_topology(xc_interface *xch, xc_cpu_policy_t
> > *policy,
> > + bool hvm)
> > +{
> > + if ( !hvm )
> > + {
> > + xc_cpu_policy_t *host;
> > + int rc;
> > +
> > + host = xc_cpu_policy_init();
> > + if ( !host )
> > + {
> > + errno = ENOMEM;
> > + return -1;
> > + }
> > +
> > + rc = xc_cpu_policy_get_system(xch, XEN_SYSCTL_cpu_policy_host,
> > host);
>
> ... retrieving the host policy, which afaict is a larger blob of data.
> Is there a particular reason for doing so?
I did that so I could assign from one CPUID policy to another, but
will revert back to using a featureset since it's indeed smaller.
> > + if ( rc )
> > + {
> > + ERROR("Failed to get host policy");
> > + xc_cpu_policy_destroy(host);
> > + return rc;
> > + }
> > +
> > +
> > + /*
> > + * On hardware without CPUID Faulting, PV guests see real topology.
> > + * As a consequence, they also need to see the host htt/cmp fields.
> > + */
> > + policy->cpuid.basic.htt = host->cpuid.basic.htt;
> > + policy->cpuid.extd.cmp_legacy = host->cpuid.extd.cmp_legacy;
> > + }
> > + else
> > + {
> > + unsigned int i;
> > +
> > + /*
> > + * Topology for HVM guests is entirely controlled by Xen. For
> > now, we
> > + * hardcode APIC_ID = vcpu_id * 2 to give the illusion of no SMT.
> > + */
> > + policy->cpuid.basic.htt = true;
> > + policy->cpuid.extd.cmp_legacy = false;
> > +
> > + /*
> > + * Leaf 1 EBX[23:16] is Maximum Logical Processors Per Package.
> > + * Update to reflect vLAPIC_ID = vCPU_ID * 2, but make sure to
> > avoid
> > + * overflow.
> > + */
> > + if ( !policy->cpuid.basic.lppp )
> > + policy->cpuid.basic.lppp = 2;
> > + else if ( !(policy->cpuid.basic.lppp & 0x80) )
> > + policy->cpuid.basic.lppp *= 2;
> > +
> > + switch ( policy->cpuid.x86_vendor )
> > + {
> > + case X86_VENDOR_INTEL:
> > + for ( i = 0; (policy->cpuid.cache.subleaf[i].type &&
> > + i < ARRAY_SIZE(policy->cpuid.cache.raw)); ++i )
> > + {
> > + policy->cpuid.cache.subleaf[i].cores_per_package =
> > + (policy->cpuid.cache.subleaf[i].cores_per_package << 1)
> > | 1;
> > + policy->cpuid.cache.subleaf[i].threads_per_cache = 0;
> > + }
> > + break;
> > +
> > + case X86_VENDOR_AMD:
> > + case X86_VENDOR_HYGON:
> > + /*
> > + * Leaf 0x80000008 ECX[15:12] is ApicIdCoreSize.
> > + * Leaf 0x80000008 ECX[7:0] is NumberOfCores (minus one).
> > + * Update to reflect vLAPIC_ID = vCPU_ID * 2. But avoid
> > + * - overflow,
> > + * - going out of sync with leaf 1 EBX[23:16],
> > + * - incrementing ApicIdCoreSize when it's zero (which changes
> > the
> > + * meaning of bits 7:0).
> > + *
> > + * UPDATE: I addition to avoiding overflow, some
>
> Nit: Would you mind switching "I" to "In" at this occasion?
Will do.
Thanks, Roger.
