linux-kernel - Re: [ANNOUNCE] PUCK Agenda - 2025.04.02

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Message-ID: <diqzplgvxbsm.fsf@ackerleytng-ctop.c.googlers.com>
Date: Tue, 29 Apr 2025 07:49:45 -0700
From: Ackerley Tng <ackerleytng@...gle.com>
To: Sean Christopherson <seanjc@...gle.com>
Cc: seanjc@...gle.com, kvm@...r.kernel.org, linux-kernel@...r.kernel.org, 
	roypat@...zon.co.uk, kalyazin@...zon.com, Fuad Tabba <tabba@...gle.com>, 
	Vishal Annapurve <vannapurve@...gle.com>, david@...hat.com
Subject: Re: [ANNOUNCE] PUCK Agenda - 2025.04.02 - No Topic

Would like to add an agenda item for 2025-04-30's PUCK meeting: KVM
memory attributes vs guest_memfd shareability.

guest_memfd tracks shareability to determine whether a page can be
faulted by the host into userspace.

pKVM does not use kvm->mem_attr_array for tracking private/shared status
of a page, and for Coco VMs like TDX, there seems to be duplicate
tracking of private/shared status in guest_memfd's shareability and in
KVM's memory attributes.

I would like to discuss a proposal for shared/private conversions to be
performed through a guest_memfd (not KVM) ioctl instead of using
KVM_SET_MEMORY_ATTRIBUTES, where Coco VMs using guest_memfd for both
shared and private memory can be able to (with some other changes around
KVM memory attributes) skip tracking private/shared in KVM's memory
attributes.

Thank you!