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

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Message-ID: <aBECik9V2uAlFKGU@google.com>
Date: Tue, 29 Apr 2025 09:47:06 -0700
From: Sean Christopherson <seanjc@...gle.com>
To: Ackerley Tng <ackerleytng@...gle.com>
Cc: 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

On Tue, Apr 29, 2025, Ackerley Tng wrote:
> 
> Would like to add an agenda item for 2025-04-30's PUCK meeting: KVM
> memory attributes vs guest_memfd shareability.

Does next week work for you?  I.e. May 7th.  I won't be able to make tomorrow's
PUCK (about to send a cancelation mail).

> 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.

Has the proposal been posted on-list anywhere?  I haven't been following the
guest_memfd threads very closely (understatement).