linux-kernel - Re: [PATCH v3 26/28] KVM: selftests: Split out helper to allocate guest mem via memfd

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Date:   Mon, 28 Feb 2022 23:36:48 +0000
From:   David Woodhouse <dwmw2@...radead.org>
To:     Sean Christopherson <seanjc@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Christian Borntraeger <borntraeger@...ux.ibm.com>,
        Janosch Frank <frankja@...ux.ibm.com>,
        Claudio Imbrenda <imbrenda@...ux.ibm.com>
Cc:     Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        David Hildenbrand <david@...hat.com>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, David Matlack <dmatlack@...gle.com>,
        Ben Gardon <bgardon@...gle.com>,
        Mingwei Zhang <mizhang@...gle.com>
Subject: Re: [PATCH v3 26/28] KVM: selftests: Split out helper to allocate
 guest mem via memfd

On Sat, 2022-02-26 at 00:15 +0000, Sean Christopherson wrote:
> Extract the code for allocating guest memory via memfd out of
> vm_userspace_mem_region_add() and into a new helper, kvm_memfd_alloc().
> A future selftest to populate a guest with the maximum amount of guest
> memory will abuse KVM's memslots to alias guest memory regions to a
> single memfd-backed host region, i.e. needs to back a guest with memfd
> memory without a 1:1 association between a memslot and a memfd instance.
> 
> No functional change intended.
> 
> Signed-off-by: Sean Christopherson <seanjc@...gle.com>

While we're at it, please can we make the whole thing go away and just
return failure #ifndef MFD_CLOEXEC, instead of breaking the build on
older userspace?

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