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

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Date:   Wed, 1 Jun 2022 13:49:17 -0700
From:   Isaku Yamahata <isaku.yamahata@...il.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     isaku.yamahata@...el.com, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, 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 Fri, May 27, 2022 at 07:38:57PM +0200,
Paolo Bonzini <pbonzini@...hat.com> wrote:

> 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?

Sure.
For next post, do you want to KVM patch series based on memfd notifier series?
-- 
Isaku Yamahata <isaku.yamahata@...il.com>