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SubjectRe: [PATCH v5 03/26] x86/hyperv: Update 'struct hv_enlightened_vmcs' definition
On Tue, Aug 02, 2022, Vitaly Kuznetsov wrote:
> Updated Hyper-V Enlightened VMCS specification lists several new
> fields for the following features:
>
> - PerfGlobalCtrl
> - EnclsExitingBitmap
> - Tsc Scaling
> - GuestLbrCtl
> - CET
> - SSP
>
> Update the definition. The updated definition is available only when
> CPUID.0x4000000A.EBX BIT(0) is '1'. Add a define for it as well.
>
> Note: The latest TLFS is available at
> https://docs.microsoft.com/en-us/virtualization/hyper-v-on-windows/tlfs/tlfs
>
> Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
> Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
> ---
> arch/x86/include/asm/hyperv-tlfs.h | 26 ++++++++++++++++++++++++--
> 1 file changed, 24 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/include/asm/hyperv-tlfs.h b/arch/x86/include/asm/hyperv-tlfs.h
> index 6f0acc45e67a..ebc27017fa48 100644
> --- a/arch/x86/include/asm/hyperv-tlfs.h
> +++ b/arch/x86/include/asm/hyperv-tlfs.h
> @@ -138,6 +138,17 @@
> #define HV_X64_NESTED_GUEST_MAPPING_FLUSH BIT(18)
> #define HV_X64_NESTED_MSR_BITMAP BIT(19)
>
> +/*
> + * Nested quirks. These are HYPERV_CPUID_NESTED_FEATURES.EBX bits.

The "quirks" part is very confusing, largely because KVM has a well-established
quirks mechanism. I also don't see "quirks" anywhere in the TLFS documentation.
Can the "Nested quirks" part simply be dropped?

> + *
> + * Note: HV_X64_NESTED_EVMCS1_2022_UPDATE is not currently documented in any
> + * published TLFS version. When the bit is set, nested hypervisor can use
> + * 'updated' eVMCSv1 specification (perf_global_ctrl, s_cet, ssp, lbr_ctl,
> + * encls_exiting_bitmap, tsc_multiplier fields which were missing in 2016
> + * specification).
> + */
> +#define HV_X64_NESTED_EVMCS1_2022_UPDATE BIT(0)

This bit is now defined[*], but the docs says it's only for perf_global_ctrl. Are
we expecting an update to the TLFS?

Indicates support for the GuestPerfGlobalCtrl and HostPerfGlobalCtrl fields
in the enlightened VMCS.

[*] https://docs.microsoft.com/en-us/virtualization/hyper-v-on-windows/tlfs/feature-discovery#hypervisor-nested-virtualization-features---0x4000000a

> +
> /*
> * This is specific to AMD and specifies that enlightened TLB flush is
> * supported. If guest opts in to this feature, ASID invalidations only
> @@ -559,9 +570,20 @@ struct hv_enlightened_vmcs {
> u64 partition_assist_page;
> u64 padding64_4[4];
> u64 guest_bndcfgs;
> - u64 padding64_5[7];
> + u64 guest_ia32_perf_global_ctrl;
> + u64 guest_ia32_s_cet;
> + u64 guest_ssp;
> + u64 guest_ia32_int_ssp_table_addr;
> + u64 guest_ia32_lbr_ctl;
> + u64 padding64_5[2];
> u64 xss_exit_bitmap;
> - u64 padding64_6[7];
> + u64 encls_exiting_bitmap;
> + u64 host_ia32_perf_global_ctrl;
> + u64 tsc_multiplier;
> + u64 host_ia32_s_cet;
> + u64 host_ssp;
> + u64 host_ia32_int_ssp_table_addr;
> + u64 padding64_6;
> } __packed;
>
> #define HV_VMX_ENLIGHTENED_CLEAN_FIELD_NONE 0
> --
> 2.35.3
>

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