linux-kernel - Re: [RFC PATCH v6 047/104] KVM: x86/tdp_mmu: Support TDX private mapping for TDP MMU

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Date:   Fri, 27 May 2022 19:38:57 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     isaku.yamahata@...el.com, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     isaku.yamahata@...il.com, erdemaktas@...gle.com,
        Sean Christopherson <seanjc@...gle.com>,
        Sagi Shahar <sagis@...gle.com>
Subject: Re: [RFC PATCH v6 047/104] KVM: x86/tdp_mmu: Support TDX private
 mapping for TDP MMU

On 5/5/22 20:14, isaku.yamahata@...el.com wrote:
> +/*
> + * Private page can't be release on mmu_notifier without losing page contents.
> + * The help, callback, from backing store is needed to allow page migration.
> + * For now, pin the page.
> + */
> +static bool kvm_faultin_pfn_private(struct kvm_vcpu *vcpu,
> +				    struct kvm_page_fault *fault, int *r)
> +{
> +	hva_t hva = gfn_to_hva_memslot(fault->slot, fault->gfn);
> +	struct page *page[1];
> +	unsigned int flags;
> +	int npages;
> +
> +	fault->map_writable = false;
> +	fault->pfn = KVM_PFN_ERR_FAULT;
> +	*r = -1;
> +	if (hva == KVM_HVA_ERR_RO_BAD || hva == KVM_HVA_ERR_BAD)
> +		return true;
> +
> +	/* TDX allows only RWX.  Read-only isn't supported. */
> +	WARN_ON_ONCE(!fault->write);
> +	flags = FOLL_WRITE | FOLL_LONGTERM;
> +
> +	npages = pin_user_pages_fast(hva, 1, flags, page);
> +	if (npages != 1)
> +		return true;
> +
> +	fault->map_writable = true;
> +	fault->pfn = page_to_pfn(page[0]);
> +	return false;
> +}
> +

This function is present also in the memfd notifier series.  For the 
next postings, can you remove all the KVM bits from the series and 
include it yourself?

Thanks,

Paolo