linux-kernel - Re: [PATCHV2 3/3] KVM: x86: add KVM_SET_MMU

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Message-ID: <YW7mXF9DNLk4fVkQ@google.com>
Date:   Wed, 20 Oct 2021 00:38:04 +0900
From:   Sergey Senozhatsky <senozhatsky@...omium.org>
To:     Paolo Bonzini <pbonzini@...hat.com>,
        David Matlack <dmatlack@...gle.com>
Cc:     Sean Christopherson <seanjc@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        Suleiman Souhlal <suleiman@...gle.com>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Sergey Senozhatsky <senozhatsky@...omium.org>
Subject: Re: [PATCHV2 3/3] KVM: x86: add KVM_SET_MMU_PREFETCH ioctl

On (21/10/20 00:32), Sergey Senozhatsky wrote:
>  static int kvm_vm_ioctl_get_clock(struct kvm *kvm, void __user *argp)
>  {
>  	struct kvm_clock_data data;
> @@ -6169,6 +6189,15 @@ long kvm_arch_vm_ioctl(struct file *filp,
>  	case KVM_X86_SET_MSR_FILTER:
>  		r = kvm_vm_ioctl_set_msr_filter(kvm, argp);
>  		break;
> +	case KVM_SET_MMU_PREFETCH: {
> +		u64 val;
> +
> +		r = -EFAULT;
> +		if (copy_from_user(&val, argp, sizeof(val)))
> +			goto out;
> +		r = kvm_arch_mmu_pte_prefetch(kvm, val);
> +		break;
> +	}

A side question: is there any value in turning this into a per-VCPU ioctl?
So that, say, on heterogeneous systems big cores can prefetch more than
little cores, for instance.