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SubjectRe: [PATCH v10 08/16] KVM: X86: Introduce KVM_HC_PAGE_ENC_STATUS hypercall
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On 2/3/21 6:38 PM, Ashish Kalra wrote:
> From: Brijesh Singh <brijesh.singh@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 patch introduces a new shared pages list implemented as a
> sorted linked list to track the shared/unencrypted regions marked by the
> guest hypercall.
>

...

> +
> + if (enc) {
> + ret = remove_shared_region(gfn_start, gfn_end,
> + &sev->shared_pages_list);
> + if (ret != -ENOMEM)
> + sev->shared_pages_list_count += ret;
> + } else {
> + ret = add_shared_region(gfn_start, gfn_end,
> + &sev->shared_pages_list);
> + if (ret > 0)
> + sev->shared_pages_list_count++;
> + }

I would move the shared_pages_list_count updates into the add/remove
functions and then just return 0 or a -EXXXX error code from those
functions. It seems simpler than "adding" ret or checking for a greater
than 0 return code.

Thanks,
Tom

> +
> + mutex_unlock(&kvm->lock);
> + return ret;
> +}
> +
> int svm_mem_enc_op(struct kvm *kvm, void __user *argp)
> {
> struct kvm_sev_cmd sev_cmd;
> @@ -1693,6 +1842,7 @@ void sev_vm_destroy(struct kvm *kvm)
>
> sev_unbind_asid(kvm, sev->handle);
> sev_asid_free(sev->asid);
> + sev->shared_pages_list_count = 0;
> }
>
> void __init sev_hardware_setup(void)
> diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
> index f923e14e87df..bb249ec625fc 100644
> --- a/arch/x86/kvm/svm/svm.c
> +++ b/arch/x86/kvm/svm/svm.c
> @@ -4536,6 +4536,8 @@ static struct kvm_x86_ops svm_x86_ops __initdata = {
> .complete_emulated_msr = svm_complete_emulated_msr,
>
> .vcpu_deliver_sipi_vector = svm_vcpu_deliver_sipi_vector,
> +
> + .page_enc_status_hc = svm_page_enc_status_hc,
> };
>
> static struct kvm_x86_init_ops svm_init_ops __initdata = {
> diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h
> index 0fe874ae5498..6437c1fa1f24 100644
> --- a/arch/x86/kvm/svm/svm.h
> +++ b/arch/x86/kvm/svm/svm.h
> @@ -79,6 +79,9 @@ struct kvm_sev_info {
> unsigned long pages_locked; /* Number of pages locked */
> struct list_head regions_list; /* List of registered regions */
> u64 ap_jump_table; /* SEV-ES AP Jump Table address */
> + /* List and count of shared pages */
> + int shared_pages_list_count;
> + struct list_head shared_pages_list;
> };
>
> struct kvm_svm {
> @@ -472,6 +475,8 @@ int nested_svm_check_exception(struct vcpu_svm *svm, unsigned nr,
> bool has_error_code, u32 error_code);
> int nested_svm_exit_special(struct vcpu_svm *svm);
> void sync_nested_vmcb_control(struct vcpu_svm *svm);
> +int svm_page_enc_status_hc(struct kvm *kvm, unsigned long gpa,
> + unsigned long npages, unsigned long enc);
>
> extern struct kvm_x86_nested_ops svm_nested_ops;
>
> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> index cc60b1fc3ee7..bcbf53851612 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -7705,6 +7705,7 @@ static struct kvm_x86_ops vmx_x86_ops __initdata = {
> .can_emulate_instruction = vmx_can_emulate_instruction,
> .apic_init_signal_blocked = vmx_apic_init_signal_blocked,
> .migrate_timers = vmx_migrate_timers,
> + .page_enc_status_hc = NULL,
>
> .msr_filter_changed = vmx_msr_filter_changed,
> .complete_emulated_msr = kvm_complete_insn_gp,
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 76bce832cade..2f17f0f9ace7 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -8162,6 +8162,12 @@ int kvm_emulate_hypercall(struct kvm_vcpu *vcpu)
> kvm_sched_yield(vcpu->kvm, a0);
> ret = 0;
> break;
> + case KVM_HC_PAGE_ENC_STATUS:
> + ret = -KVM_ENOSYS;
> + if (kvm_x86_ops.page_enc_status_hc)
> + ret = kvm_x86_ops.page_enc_status_hc(vcpu->kvm,
> + a0, a1, a2);
> + break;
> 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
>

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