Re: [PATCH v10 21/50] KVM: SEV: Add support to handle AP reset MSR protocol

[Borislav Petkov]

On Mon, Oct 16, 2023 at 08:27:50AM -0500, Michael Roth wrote:
> From: Tom Lendacky <thomas.lendacky@xxxxxxx>
> 
> Add support for AP Reset Hold being invoked using the GHCB MSR protocol,
> available in version 2 of the GHCB specification.
> 
> Signed-off-by: Tom Lendacky <thomas.lendacky@xxxxxxx>
> Signed-off-by: Brijesh Singh <brijesh.singh@xxxxxxx>
> Signed-off-by: Ashish Kalra <ashish.kalra@xxxxxxx>
> ---
>  arch/x86/include/asm/sev-common.h |  2 ++
>  arch/x86/kvm/svm/sev.c            | 56 ++++++++++++++++++++++++++-----
>  arch/x86/kvm/svm/svm.h            |  1 +
>  3 files changed, 51 insertions(+), 8 deletions(-)
> 
> diff --git a/arch/x86/include/asm/sev-common.h b/arch/x86/include/asm/sev-common.h
> index 93ec8c12c91d..57ced29264ce 100644
> --- a/arch/x86/include/asm/sev-common.h
> +++ b/arch/x86/include/asm/sev-common.h
> @@ -56,6 +56,8 @@
>  /* AP Reset Hold */
>  #define GHCB_MSR_AP_RESET_HOLD_REQ	0x006
>  #define GHCB_MSR_AP_RESET_HOLD_RESP	0x007
> +#define GHCB_MSR_AP_RESET_HOLD_RESULT_POS	12
> +#define GHCB_MSR_AP_RESET_HOLD_RESULT_MASK	GENMASK_ULL(51, 0)

Align vertically pls.

>  /* GHCB GPA Register */
>  #define GHCB_MSR_REG_GPA_REQ		0x012
> diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
> index 6ee925d66648..4f895a7201ed 100644
> --- a/arch/x86/kvm/svm/sev.c
> +++ b/arch/x86/kvm/svm/sev.c
> @@ -65,6 +65,10 @@ module_param_named(debug_swap, sev_es_debug_swap_enabled, bool, 0444);
>  #define sev_es_debug_swap_enabled false
>  #endif /* CONFIG_KVM_AMD_SEV */
>  
> +#define AP_RESET_HOLD_NONE		0
> +#define AP_RESET_HOLD_NAE_EVENT		1
> +#define AP_RESET_HOLD_MSR_PROTO		2
> +
>  static u8 sev_enc_bit;
>  static DECLARE_RWSEM(sev_deactivate_lock);
>  static DEFINE_MUTEX(sev_bitmap_lock);
> @@ -2594,6 +2598,9 @@ static int sev_es_validate_vmgexit(struct vcpu_svm *svm)
>  
>  void sev_es_unmap_ghcb(struct vcpu_svm *svm)
>  {
> +	/* Clear any indication that the vCPU is in a type of AP Reset Hold */
> +	svm->sev_es.ap_reset_hold_type = AP_RESET_HOLD_NONE;
> +
>  	if (!svm->sev_es.ghcb)
>  		return;
>  
> @@ -2805,6 +2812,22 @@ static int sev_handle_vmgexit_msr_protocol(struct vcpu_svm *svm)
>  				  GHCB_MSR_INFO_POS);
>  		break;
>  	}
> +	case GHCB_MSR_AP_RESET_HOLD_REQ:
> +		svm->sev_es.ap_reset_hold_type = AP_RESET_HOLD_MSR_PROTO;
> +		ret = kvm_emulate_ap_reset_hold(&svm->vcpu);
> +
> +		/*
> +		 * Preset the result to a non-SIPI return and then only set
> +		 * the result to non-zero when delivering a SIPI.
> +		 */
> +		set_ghcb_msr_bits(svm, 0,
> +				  GHCB_MSR_AP_RESET_HOLD_RESULT_MASK,
> +				  GHCB_MSR_AP_RESET_HOLD_RESULT_POS);

Yikes, those defines are a mouthful.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette