linux-kernel - Re: [RFC 11/33] KVM: x86: hyper-v: Handle GET/SET_VP

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Message-ID: <b9c6ad26-ce8b-45f3-b856-8e6be2497f6e@amazon.com>
Date:   Wed, 8 Nov 2023 13:14:39 +0100
From:   Alexander Graf <graf@...zon.com>
To:     Nicolas Saenz Julienne <nsaenz@...zon.com>, <kvm@...r.kernel.org>
CC:     <linux-kernel@...r.kernel.org>, <linux-hyperv@...r.kernel.org>,
        <pbonzini@...hat.com>, <seanjc@...gle.com>, <vkuznets@...hat.com>,
        <anelkz@...zon.com>, <dwmw@...zon.co.uk>, <jgowans@...zon.com>,
        <corbert@....net>, <kys@...rosoft.com>, <haiyangz@...rosoft.com>,
        <decui@...rosoft.com>, <x86@...nel.org>,
        <linux-doc@...r.kernel.org>
Subject: Re: [RFC 11/33] KVM: x86: hyper-v: Handle GET/SET_VP_REGISTER hcall
 in user-space


On 08.11.23 12:17, Nicolas Saenz Julienne wrote:
> Let user-space handle HVCALL_GET_VP_REGISTERS and
> HVCALL_SET_VP_REGISTERS through the KVM_EXIT_HYPERV_HVCALL exit reason.
> Additionally, expose the cpuid bit.
>
> Signed-off-by: Nicolas Saenz Julienne <nsaenz@...zon.com>
> ---
>   arch/x86/kvm/hyperv.c             | 9 +++++++++
>   include/asm-generic/hyperv-tlfs.h | 1 +
>   2 files changed, 10 insertions(+)
>
> diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
> index caaa859932c5..a3970d52eef1 100644
> --- a/arch/x86/kvm/hyperv.c
> +++ b/arch/x86/kvm/hyperv.c
> @@ -2456,6 +2456,9 @@ static void kvm_hv_write_xmm(struct kvm_hyperv_xmm_reg *xmm)
>   
>   static bool kvm_hv_is_xmm_output_hcall(u16 code)
>   {
> +	if (code == HVCALL_GET_VP_REGISTERS)
> +		return true;
> +
>   	return false;
>   }
>   
> @@ -2520,6 +2523,8 @@ static bool is_xmm_fast_hypercall(struct kvm_hv_hcall *hc)
>   	case HVCALL_FLUSH_VIRTUAL_ADDRESS_LIST_EX:
>   	case HVCALL_FLUSH_VIRTUAL_ADDRESS_SPACE_EX:
>   	case HVCALL_SEND_IPI_EX:
> +	case HVCALL_GET_VP_REGISTERS:
> +	case HVCALL_SET_VP_REGISTERS:
>   		return true;
>   	}
>   
> @@ -2738,6 +2743,9 @@ int kvm_hv_hypercall(struct kvm_vcpu *vcpu)
>   			break;
>   		}
>   		goto hypercall_userspace_exit;
> +	case HVCALL_GET_VP_REGISTERS:
> +	case HVCALL_SET_VP_REGISTERS:
> +		goto hypercall_userspace_exit;
>   	default:
>   		ret = HV_STATUS_INVALID_HYPERCALL_CODE;
>   		break;
> @@ -2903,6 +2911,7 @@ int kvm_get_hv_cpuid(struct kvm_vcpu *vcpu, struct kvm_cpuid2 *cpuid,
>   			ent->ebx |= HV_POST_MESSAGES;
>   			ent->ebx |= HV_SIGNAL_EVENTS;
>   			ent->ebx |= HV_ENABLE_EXTENDED_HYPERCALLS;
> +			ent->ebx |= HV_ACCESS_VP_REGISTERS;


Do we need to guard this?


Alex




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