Re: [PATCH 2/2] x86/cpuid: support LFENCE always serializing CPUID bit

[Jan Beulich <jbeulich@xxxxxxxx>]

On 14.04.2021 13:04, Roger Pau Monne wrote:
> @@ -264,6 +265,38 @@ struct cpuid_policy
>              };
>              uint32_t nc:8, :4, apic_id_size:4, :16;
>              uint32_t /* d */:32;
> +
> +            uint64_t :64, :64; /* Leaf 0x80000009. */
> +            uint64_t :64, :64; /* Leaf 0x8000000a - SVM rev and features. */
> +            uint64_t :64, :64; /* Leaf 0x8000000b. */
> +            uint64_t :64, :64; /* Leaf 0x8000000c. */
> +            uint64_t :64, :64; /* Leaf 0x8000000d. */
> +            uint64_t :64, :64; /* Leaf 0x8000000e. */
> +            uint64_t :64, :64; /* Leaf 0x8000000f. */
> +            uint64_t :64, :64; /* Leaf 0x80000010. */
> +            uint64_t :64, :64; /* Leaf 0x80000011. */
> +            uint64_t :64, :64; /* Leaf 0x80000012. */
> +            uint64_t :64, :64; /* Leaf 0x80000013. */
> +            uint64_t :64, :64; /* Leaf 0x80000014. */
> +            uint64_t :64, :64; /* Leaf 0x80000015. */
> +            uint64_t :64, :64; /* Leaf 0x80000016. */
> +            uint64_t :64, :64; /* Leaf 0x80000017. */
> +            uint64_t :64, :64; /* Leaf 0x80000018. */
> +            uint64_t :64, :64; /* Leaf 0x80000019 - TLB 1GB Identifiers. */
> +            uint64_t :64, :64; /* Leaf 0x8000001a - Performance related 
> info. */
> +            uint64_t :64, :64; /* Leaf 0x8000001b - IBS feature information. 
> */
> +            uint64_t :64, :64; /* Leaf 0x8000001c. */
> +            uint64_t :64, :64; /* Leaf 0x8000001d - Cache properties. */
> +            uint64_t :64, :64; /* Leaf 0x8000001e - Extd APIC/Core/Node IDs. 
> */
> +            uint64_t :64, :64; /* Leaf 0x8000001f - AMD Secure Encryption. */
> +            uint64_t :64, :64; /* Leaf 0x80000020 - Platform QoS. */
> +
> +            /* Leaf 0x80000021 - Extended Feature 2 */
> +            union {
> +                uint32_t e21a;
> +                struct { DECL_BITFIELD(e21a); };
> +            };
> +            uint32_t /* b */:32, /* c */:32, /* d */:32;
>          };
>      } extd;

Due to the effect of this on what guests get to see, I think this
wants to take my "x86/CPUID: shrink max_{,sub}leaf fields according
to actual leaf contents" as a prereq, which in turn may better
remain on top of "x86/CPUID: adjust extended leaves out of range
clearing" (both are neighbors in that over 4 months old series,
fair parts of which could imo go in irrespective of the unsettled
dispute on xvmalloc() - unfortunately I had made that patch 2 of
the series, not expecting it to be blocked for so long, and then
presumably signaling to others that the rest of the series is also
blocked).

Jan