linux-kernel - [RFC PATCH v2 0/2] KVM: guest_memfd: use write for population

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Message-ID: <20241129123929.64790-1-kalyazin@amazon.com>
Date: Fri, 29 Nov 2024 12:39:27 +0000
From: Nikita Kalyazin <kalyazin@...zon.com>
To: <pbonzini@...hat.com>, <shuah@...nel.org>, <kvm@...r.kernel.org>,
	<linux-kselftest@...r.kernel.org>, <linux-kernel@...r.kernel.org>
CC: <linux-mm@...ck.org>, <michael.day@....com>, <david@...hat.com>,
	<quic_eberman@...cinc.com>, <jthoughton@...gle.com>, <brijesh.singh@....com>,
	<michael.roth@....com>, <graf@...zon.de>, <jgowans@...zon.com>,
	<roypat@...zon.co.uk>, <derekmn@...zon.com>, <nsaenz@...zon.es>,
	<xmarcalx@...zon.com>, <kalyazin@...zon.com>
Subject: [RFC PATCH v2 0/2] KVM: guest_memfd: use write for population

As discussed in the v1 [1], with guest_memfd moving from KVM to mm, it
is more practical to have a non-KVM-specific API to populate guest
memory in a generic way.  The series proposes using the write syscall
for this purpose instead of a KVM ioctl as in the v1.  The approach also
has an advantage that the guest_memfd handle can be sent to another
process that would be responsible for population.  I also included a
suggestion from Mike Day for excluding the code from compilation if AMD
SEV is configured.

There is a potential for refactoring of the kvm_gmem_populate to extract
common parts with the write.  I did not do that in this series yet to
keep it clear what the write would do and get feedback on whether
write's behaviour is sensible.

Nikita

[1]: https://lore.kernel.org/kvm/20241024095429.54052-1-kalyazin@amazon.com/T/

Nikita Kalyazin (2):
  KVM: guest_memfd: add generic population via write
  KVM: selftests: update guest_memfd write tests

 .../testing/selftests/kvm/guest_memfd_test.c  | 85 +++++++++++++++++--
 virt/kvm/guest_memfd.c                        | 79 +++++++++++++++++
 2 files changed, 158 insertions(+), 6 deletions(-)

base-commit: 1508bae37044ebffd7c7e09915f041936f338123
-- 
2.40.1