linux-kernel - Re: [PATCH v2] Add KVM_EXIT_SHUTDOWN metadata for SEV-ES

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Date:   Fri, 25 Mar 2022 16:28:54 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Peter Gonda <pgonda@...gle.com>, kvm@...r.kernel.org
Cc:     Borislav Petkov <bp@...en8.de>,
        Tom Lendacky <thomas.lendacky@....com>,
        Brijesh Singh <brijesh.singh@....com>,
        Joerg Roedel <jroedel@...e.de>, Marc Orr <marcorr@...gle.com>,
        Sean Christopherson <seanjc@...gle.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] Add KVM_EXIT_SHUTDOWN metadata for SEV-ES

On 3/25/22 16:27, Peter Gonda wrote:
> SEV-ES guests can request termination using the GHCB's MSR protocol. See
> AMD's GHCB spec section '4.1.13 Termination Request'. Currently when a
> guest does this the userspace VMM sees an KVM_EXIT_UNKNOWN (-EVINAL)
> return code from KVM_RUN. By adding a KVM_EXIT_SHUTDOWN_ENTRY to kvm_run
> struct the userspace VMM can clear see the guest has requested a SEV-ES
> termination including the termination reason code set and reason code.
> 
> Signed-off-by: Peter Gonda <pgonda@...gle.com>
> Cc: Paolo Bonzini <pbonzini@...hat.com>
> Cc: Borislav Petkov <bp@...en8.de>
> Cc: Tom Lendacky <thomas.lendacky@....com>
> Cc: Brijesh Singh <brijesh.singh@....com>
> Cc: Joerg Roedel <jroedel@...e.de>
> Cc: Marc Orr <marcorr@...gle.com>
> Cc: Sean Christopherson <seanjc@...gle.com>
> Cc: kvm@...r.kernel.org
> Cc: linux-kernel@...r.kernel.org

This is missing an update to Documentation/.

Paolo

> ---
> 
> V2
>   * Add KVM_CAP_EXIT_SHUTDOWN_REASON check for KVM_CHECK_EXTENSION.
> 
> Tested by making an SEV-ES guest call sev_es_terminate() with hardcoded
> reason code set and reason code and then observing the codes from the
> userspace VMM in the kvm_run.shutdown.data fields.
> 
> ---
>   arch/x86/kvm/svm/sev.c   |  9 +++++++--
>   include/uapi/linux/kvm.h | 13 +++++++++++++
>   virt/kvm/kvm_main.c      |  1 +
>   3 files changed, 21 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
> index 75fa6dd268f0..5f9d37dd3f6f 100644
> --- a/arch/x86/kvm/svm/sev.c
> +++ b/arch/x86/kvm/svm/sev.c
> @@ -2735,8 +2735,13 @@ static int sev_handle_vmgexit_msr_protocol(struct vcpu_svm *svm)
>   		pr_info("SEV-ES guest requested termination: %#llx:%#llx\n",
>   			reason_set, reason_code);
>   
> -		ret = -EINVAL;
> -		break;
> +		vcpu->run->exit_reason = KVM_EXIT_SHUTDOWN;
> +		vcpu->run->shutdown.reason = KVM_SHUTDOWN_SEV_TERM;
> +		vcpu->run->shutdown.ndata = 2;
> +		vcpu->run->shutdown.data[0] = reason_set;
> +		vcpu->run->shutdown.data[1] = reason_code;
> +
> +		return 0;
>   	}
>   	default:
>   		/* Error, keep GHCB MSR value as-is */
> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> index 8616af85dc5d..017c03421c48 100644
> --- a/include/uapi/linux/kvm.h
> +++ b/include/uapi/linux/kvm.h
> @@ -271,6 +271,12 @@ struct kvm_xen_exit {
>   #define KVM_EXIT_XEN              34
>   #define KVM_EXIT_RISCV_SBI        35
>   
> +/* For KVM_EXIT_SHUTDOWN */
> +/* Standard VM shutdown request. No additional metadata provided. */
> +#define KVM_SHUTDOWN_REQ	0
> +/* SEV-ES termination request */
> +#define KVM_SHUTDOWN_SEV_TERM	1
> +
>   /* For KVM_EXIT_INTERNAL_ERROR */
>   /* Emulate instruction failed. */
>   #define KVM_INTERNAL_ERROR_EMULATION	1
> @@ -311,6 +317,12 @@ struct kvm_run {
>   		struct {
>   			__u64 hardware_exit_reason;
>   		} hw;
> +		/* KVM_EXIT_SHUTDOWN */
> +		struct {
> +			__u64 reason;
> +			__u32 ndata;
> +			__u64 data[16];
> +		} shutdown;
>   		/* KVM_EXIT_FAIL_ENTRY */
>   		struct {
>   			__u64 hardware_entry_failure_reason;
> @@ -1145,6 +1157,7 @@ struct kvm_ppc_resize_hpt {
>   #define KVM_CAP_PMU_CAPABILITY 212
>   #define KVM_CAP_DISABLE_QUIRKS2 213
>   #define KVM_CAP_VM_TSC_CONTROL 214
> +#define KVM_CAP_EXIT_SHUTDOWN_REASON 215
>   
>   #ifdef KVM_CAP_IRQ_ROUTING
>   
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index 70e05af5ebea..03b6e472f32c 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -4299,6 +4299,7 @@ static long kvm_vm_ioctl_check_extension_generic(struct kvm *kvm, long arg)
>   	case KVM_CAP_CHECK_EXTENSION_VM:
>   	case KVM_CAP_ENABLE_CAP_VM:
>   	case KVM_CAP_HALT_POLL:
> +	case KVM_CAP_EXIT_SHUTDOWN_REASON:
>   		return 1;
>   #ifdef CONFIG_KVM_MMIO
>   	case KVM_CAP_COALESCED_MMIO: