Message-ID: <12f88382-e1eb-4e40-9e47-dafb79a7f102@redhat.com>
Date: Fri, 13 Jun 2025 09:36:18 +0200
From: David Hildenbrand <david@...hat.com>
To: Michael Roth <michael.roth@....com>, kvm@...r.kernel.org
Cc: linux-coco@...ts.linux.dev, linux-mm@...ck.org,
 linux-kernel@...r.kernel.org, tabba@...gle.com, vannapurve@...gle.com,
 ackerleytng@...gle.com, ira.weiny@...el.com, thomas.lendacky@....com,
 pbonzini@...hat.com, seanjc@...gle.com, vbabka@...e.cz, joro@...tes.org,
 pratikrajesh.sampat@....com, liam.merwick@...cle.com, yan.y.zhao@...el.com,
 aik@....com
Subject: Re: [PATCH RFC v1 0/5] KVM: guest_memfd: Support in-place conversion
 for CoCo VMs

On 13.06.25 02:53, Michael Roth wrote:
> This patchset is also available at:
> 
>    https://github.com/amdese/linux/commits/snp-inplace-conversion-rfc1
> 
> and is based on top of the following patches plucked from Ackerley's
> HugeTLBFS series[1], which add support for tracking/converting guest_memfd
> pages between private/shared states so the same physical pages can be used
> to handle both private/shared accesses by the guest or by userspace:
> 
>    KVM: selftests: Update script to map shared memory from guest_memfd
>    KVM: selftests: Update private_mem_conversions_test to mmap guest_memfd
>    KVM: selftests: Add script to exercise private_mem_conversions_test
>    KVM: selftests: Test conversion flows for guest_memfd
>    KVM: selftests: Allow cleanup of ucall_pool from host
>    KVM: selftests: Refactor vm_mem_add to be more flexible
>    KVM: selftests: Test faulting with respect to GUEST_MEMFD_FLAG_INIT_PRIVATE
>    KVM: selftests: Test flag validity after guest_memfd supports conversions
>    KVM: guest_memfd: Add CAP KVM_CAP_GMEM_CONVERSION
>    KVM: Query guest_memfd for private/shared status
>    KVM: guest_memfd: Skip LRU for guest_memfd folios
>    KVM: guest_memfd: Introduce KVM_GMEM_CONVERT_SHARED/PRIVATE ioctls
>    KVM: selftests: Update guest_memfd_test for INIT_PRIVATE flag
>    KVM: guest_memfd: Introduce and use shareability to guard faulting
>    KVM: guest_memfd: Make guest mem use guest mem inodes instead of anonymous inodes
>    fs: Refactor to provide function that allocates a secure anonymous inode
> 
>    "[RFC PATCH v2 00/51] 1G page support for guest_memfd"
>    https://lore.kernel.org/lkml/cover.1747264138.git.ackerleytng@google.com/
> 
> which is in turn based on the following series[2] from Fuad which implements
> the initial support for guest_memfd to manage shared memory and allow it to
> be mmap()'d into userspace:
> 
>    "[PATCH v12 00/18] KVM: Mapping guest_memfd backed memory at the host for software protected VMs"
>    https://lore.kernel.org/kvm/20250611133330.1514028-1-tabba@google.com/
> 
> (One of the main goals of posting this series in it's current form is to
> identify the common set of dependencies to enable in-place conversion
> support for SEV-SNP, TDX, and pKVM, which have been coined "stage 2"
> according to upstreaming plans discussed during guest_memfd bi-weekly calls
> and summarized by David here[3] (Fuad's series[2] being "stage 1"),
> so please feel free to chime in here if there's any feedback on whether
> something like the above set of dependencies is a reasonable starting point
> for "stage 2" and how best to handle setting up a common tree to track this
> dependency.)

If nobody else volunteers, I can soon start maintaining a guest_memfd 
preview tree. I suspect a good starting point would be once stage-2 is 
posted separately.

-- 
Cheers,

David / dhildenb

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