linux-kernel - Re: [PATCH RFC v8 09/56] KVM: SEV: Handle memory backed by restricted memfd

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Date:   Fri, 3 Mar 2023 15:05:09 +0100
From:   Vlastimil Babka <vbabka@...e.cz>
To:     Michael Roth <michael.roth@....com>, kvm@...r.kernel.org
Cc:     linux-coco@...ts.linux.dev, linux-mm@...ck.org,
        linux-crypto@...r.kernel.org, x86@...nel.org,
        linux-kernel@...r.kernel.org, tglx@...utronix.de, mingo@...hat.com,
        jroedel@...e.de, thomas.lendacky@....com, hpa@...or.com,
        ardb@...nel.org, pbonzini@...hat.com, seanjc@...gle.com,
        vkuznets@...hat.com, jmattson@...gle.com, luto@...nel.org,
        dave.hansen@...ux.intel.com, slp@...hat.com, pgonda@...gle.com,
        peterz@...radead.org, srinivas.pandruvada@...ux.intel.com,
        rientjes@...gle.com, dovmurik@...ux.ibm.com, tobin@....com,
        bp@...en8.de, kirill@...temov.name, ak@...ux.intel.com,
        tony.luck@...el.com, marcorr@...gle.com,
        sathyanarayanan.kuppuswamy@...ux.intel.com, alpergun@...gle.com,
        dgilbert@...hat.com, jarkko@...nel.org, ashish.kalra@....com,
        nikunj.dadhania@....com, Nikunj A Dadhania <nikunj@....com>
Subject: Re: [PATCH RFC v8 09/56] KVM: SEV: Handle memory backed by restricted
 memfd

On 2/20/23 19:38, Michael Roth wrote:
> From: Nikunj A Dadhania <nikunj@....com>
> 
> Do not pin the guest memory backed by a restrictedmem backend, as
> pages in the restrictedmem are already pinned. Instead, populate the
> pages array for these guests using the already-pinned pages provided by

IIUC the "already pinned" became "effectively unmovable and unevictable"
since the earlier versions, so that would be more accurate now?

> +static int sev_private_mem_get_pages(struct kvm *kvm, unsigned long addr,
> +				     unsigned long size, unsigned long npages,
> +				     struct page **pages)
> +{
> +	return kvm_vm_do_hva_range_op(kvm, addr, addr + size,
> +				      sev_private_mem_get_pages_handler, pages);
> +}
> +
>  /*
>   * Legacy SEV guest pin the pages and return the array populated with pinned
>   * pages.
> + *
> + * SEV guests using restricted memfd backend, pages are already marked as
> + * unmovable and unevictable. Populate the pages array for these guests using
> + * restrictedmem get_pfn.

Right.