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From: Paolo Bonzini <pbonzini@redhat.com>
To: Ashish Kalra <Ashish.Kalra@amd.com>
Cc: tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com,
	joro@8bytes.org, bp@suse.de, thomas.lendacky@amd.com,
	x86@kernel.org, kvm@vger.kernel.org,
	linux-kernel@vger.kernel.org, srutherford@google.com,
	seanjc@google.com, venu.busireddy@oracle.com,
	brijesh.singh@amd.com
Subject: Re: [PATCH v13 08/12] KVM: X86: Introduce KVM_HC_PAGE_ENC_STATUS hypercall
Date: Tue, 20 Apr 2021 13:10:36 +0200
Message-ID: <6e6b4e8c-bbfa-fd58-c1e8-895a157762fe@redhat.com> (raw)
In-Reply-To: <93d7f2c2888315adc48905722574d89699edde33.1618498113.git.ashish.kalra@amd.com>

On 15/04/21 17:57, Ashish Kalra wrote:
> From: Ashish Kalra <ashish.kalra@amd.com>
> 
> This hypercall is used by the SEV guest to notify a change in the page
> encryption status to the hypervisor. The hypercall should be invoked
> only when the encryption attribute is changed from encrypted -> decrypted
> and vice versa. By default all guest pages are considered encrypted.
> 
> The hypercall exits to userspace to manage the guest shared regions and
> integrate with the userspace VMM's migration code.

I think this should be exposed to userspace as a capability, rather than 
as a CPUID bit.  Userspace then can enable the capability and set the 
CPUID bit if it wants.

The reason is that userspace could pass KVM_GET_SUPPORTED_CPUID to
KVM_SET_CPUID2 and the hypercall then would break the guest.

Paolo

> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: "H. Peter Anvin" <hpa@zytor.com>
> Cc: Paolo Bonzini <pbonzini@redhat.com>
> Cc: Joerg Roedel <joro@8bytes.org>
> Cc: Borislav Petkov <bp@suse.de>
> Cc: Tom Lendacky <thomas.lendacky@amd.com>
> Cc: x86@kernel.org
> Cc: kvm@vger.kernel.org
> Cc: linux-kernel@vger.kernel.org
> Reviewed-by: Steve Rutherford <srutherford@google.com>
> Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
> Signed-off-by: Ashish Kalra <ashish.kalra@amd.com>
> Co-developed-by: Sean Christopherson <seanjc@google.com>
> Signed-off-by: Sean Christopherson <seanjc@google.com>
> ---
>   Documentation/virt/kvm/hypercalls.rst | 15 ++++++++++++++
>   arch/x86/include/asm/kvm_host.h       |  2 ++
>   arch/x86/kvm/svm/sev.c                |  1 +
>   arch/x86/kvm/x86.c                    | 29 +++++++++++++++++++++++++++
>   include/uapi/linux/kvm_para.h         |  1 +
>   5 files changed, 48 insertions(+)
> 
> diff --git a/Documentation/virt/kvm/hypercalls.rst b/Documentation/virt/kvm/hypercalls.rst
> index ed4fddd364ea..7aff0cebab7c 100644
> --- a/Documentation/virt/kvm/hypercalls.rst
> +++ b/Documentation/virt/kvm/hypercalls.rst
> @@ -169,3 +169,18 @@ a0: destination APIC ID
>   
>   :Usage example: When sending a call-function IPI-many to vCPUs, yield if
>   	        any of the IPI target vCPUs was preempted.
> +
> +
> +8. KVM_HC_PAGE_ENC_STATUS
> +-------------------------
> +:Architecture: x86
> +:Status: active
> +:Purpose: Notify the encryption status changes in guest page table (SEV guest)
> +
> +a0: the guest physical address of the start page
> +a1: the number of pages
> +a2: encryption attribute
> +
> +   Where:
> +	* 1: Encryption attribute is set
> +	* 0: Encryption attribute is cleared
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index 3768819693e5..42eb0fe3df5d 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -1050,6 +1050,8 @@ struct kvm_arch {
>   
>   	bool bus_lock_detection_enabled;
>   
> +	bool page_enc_hc_enable;
> +
>   	/* Deflect RDMSR and WRMSR to user space when they trigger a #GP */
>   	u32 user_space_msr_mask;
>   	struct kvm_x86_msr_filter __rcu *msr_filter;
> diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
> index c9795a22e502..5184a0c0131a 100644
> --- a/arch/x86/kvm/svm/sev.c
> +++ b/arch/x86/kvm/svm/sev.c
> @@ -197,6 +197,7 @@ static int sev_guest_init(struct kvm *kvm, struct kvm_sev_cmd *argp)
>   	sev->active = true;
>   	sev->asid = asid;
>   	INIT_LIST_HEAD(&sev->regions_list);
> +	kvm->arch.page_enc_hc_enable = true;
>   
>   	return 0;
>   
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index f7d12fca397b..e8986478b653 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -8208,6 +8208,13 @@ static void kvm_sched_yield(struct kvm *kvm, unsigned long dest_id)
>   		kvm_vcpu_yield_to(target);
>   }
>   
> +static int complete_hypercall_exit(struct kvm_vcpu *vcpu)
> +{
> +	kvm_rax_write(vcpu, vcpu->run->hypercall.ret);
> +	++vcpu->stat.hypercalls;
> +	return kvm_skip_emulated_instruction(vcpu);
> +}
> +
>   int kvm_emulate_hypercall(struct kvm_vcpu *vcpu)
>   {
>   	unsigned long nr, a0, a1, a2, a3, ret;
> @@ -8273,6 +8280,28 @@ int kvm_emulate_hypercall(struct kvm_vcpu *vcpu)
>   		kvm_sched_yield(vcpu->kvm, a0);
>   		ret = 0;
>   		break;
> +	case KVM_HC_PAGE_ENC_STATUS: {
> +		u64 gpa = a0, npages = a1, enc = a2;
> +
> +		ret = -KVM_ENOSYS;
> +		if (!vcpu->kvm->arch.page_enc_hc_enable)
> +			break;
> +
> +		if (!PAGE_ALIGNED(gpa) || !npages ||
> +		    gpa_to_gfn(gpa) + npages <= gpa_to_gfn(gpa)) {
> +			ret = -EINVAL;
> +			break;
> +		}
> +
> +		vcpu->run->exit_reason        = KVM_EXIT_HYPERCALL;
> +		vcpu->run->hypercall.nr       = KVM_HC_PAGE_ENC_STATUS;
> +		vcpu->run->hypercall.args[0]  = gpa;
> +		vcpu->run->hypercall.args[1]  = npages;
> +		vcpu->run->hypercall.args[2]  = enc;
> +		vcpu->run->hypercall.longmode = op_64_bit;
> +		vcpu->arch.complete_userspace_io = complete_hypercall_exit;
> +		return 0;
> +	}
>   	default:
>   		ret = -KVM_ENOSYS;
>   		break;
> diff --git a/include/uapi/linux/kvm_para.h b/include/uapi/linux/kvm_para.h
> index 8b86609849b9..847b83b75dc8 100644
> --- a/include/uapi/linux/kvm_para.h
> +++ b/include/uapi/linux/kvm_para.h
> @@ -29,6 +29,7 @@
>   #define KVM_HC_CLOCK_PAIRING		9
>   #define KVM_HC_SEND_IPI		10
>   #define KVM_HC_SCHED_YIELD		11
> +#define KVM_HC_PAGE_ENC_STATUS		12
>   
>   /*
>    * hypercalls use architecture specific
> 


  reply index

Thread overview: 43+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-15 15:52 [PATCH v13 00/12] Add AMD SEV guest live migration support Ashish Kalra
2021-04-15 15:53 ` [PATCH v13 01/12] KVM: SVM: Add KVM_SEV SEND_START command Ashish Kalra
2021-04-20  8:50   ` Paolo Bonzini
2021-04-15 15:53 ` [PATCH v13 02/12] KVM: SVM: Add KVM_SEND_UPDATE_DATA command Ashish Kalra
2021-04-15 15:54 ` [PATCH v13 03/12] KVM: SVM: Add KVM_SEV_SEND_FINISH command Ashish Kalra
2021-04-15 15:54 ` [PATCH v13 04/12] KVM: SVM: Add support for KVM_SEV_RECEIVE_START command Ashish Kalra
2021-04-20  8:38   ` Paolo Bonzini
2021-04-20  9:18     ` Paolo Bonzini
2021-04-15 15:55 ` [PATCH v13 05/12] KVM: SVM: Add KVM_SEV_RECEIVE_UPDATE_DATA command Ashish Kalra
2021-04-20  8:40   ` Paolo Bonzini
2021-04-20  8:43     ` Paolo Bonzini
2021-04-15 15:55 ` [PATCH v13 06/12] KVM: SVM: Add KVM_SEV_RECEIVE_FINISH command Ashish Kalra
2021-04-15 15:56 ` [PATCH v13 07/12] KVM: x86: Add AMD SEV specific Hypercall3 Ashish Kalra
2021-04-15 15:57 ` [PATCH v13 08/12] KVM: X86: Introduce KVM_HC_PAGE_ENC_STATUS hypercall Ashish Kalra
2021-04-20 11:10   ` Paolo Bonzini [this message]
2021-04-20 17:24     ` Sean Christopherson
2021-04-15 15:57 ` [PATCH v13 09/12] mm: x86: Invoke hypercall when page encryption status is changed Ashish Kalra
2021-04-20  9:39   ` Paolo Bonzini
2021-04-21 10:05   ` Borislav Petkov
2021-04-21 12:00     ` Paolo Bonzini
2021-04-21 14:09       ` Borislav Petkov
2021-04-21 12:12     ` Ashish Kalra
2021-04-21 13:50       ` Brijesh Singh
2021-04-21 13:52       ` Borislav Petkov
2021-04-15 15:58 ` [PATCH v13 10/12] KVM: x86: Introduce new KVM_FEATURE_SEV_LIVE_MIGRATION feature & Custom MSR Ashish Kalra
2021-04-19 23:06   ` Sean Christopherson
2021-04-20 10:49     ` Paolo Bonzini
2021-04-20  9:47   ` Paolo Bonzini
2021-04-15 15:58 ` [PATCH v13 11/12] EFI: Introduce the new AMD Memory Encryption GUID Ashish Kalra
2021-04-15 16:01 ` [PATCH v13 12/12] x86/kvm: Add guest support for detecting and enabling SEV Live Migration feature Ashish Kalra
2021-04-20 10:52   ` Paolo Bonzini
2021-04-21 14:44   ` Borislav Petkov
2021-04-21 15:22     ` Ashish Kalra
2021-04-21 15:32       ` Borislav Petkov
2021-04-21 15:38     ` Paolo Bonzini
2021-04-21 18:48       ` Ashish Kalra
2021-04-21 19:19         ` Ashish Kalra
2021-04-16 21:43 ` [PATCH v13 00/12] Add AMD SEV guest live migration support Steve Rutherford
2021-04-19 14:40   ` Ashish Kalra
2021-04-20 11:11 ` Paolo Bonzini
2021-04-20 18:51   ` Borislav Petkov
2021-04-20 19:08     ` Paolo Bonzini
2021-04-20 20:28       ` Borislav Petkov

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