* [ANNOUNCE] PUCK Agenda - 2025.04.02 - No Topic
@ 2025-04-02 0:29 Sean Christopherson
2025-04-29 14:49 ` Ackerley Tng
0 siblings, 1 reply; 4+ messages in thread
From: Sean Christopherson @ 2025-04-02 0:29 UTC (permalink / raw)
To: Sean Christopherson; +Cc: kvm, linux-kernel
No scheduled topic for tomorrow, but PUCK is back on this week.
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [ANNOUNCE] PUCK Agenda - 2025.04.02 - No Topic
2025-04-02 0:29 [ANNOUNCE] PUCK Agenda - 2025.04.02 - No Topic Sean Christopherson
@ 2025-04-29 14:49 ` Ackerley Tng
2025-04-29 16:47 ` Sean Christopherson
0 siblings, 1 reply; 4+ messages in thread
From: Ackerley Tng @ 2025-04-29 14:49 UTC (permalink / raw)
To: Sean Christopherson
Cc: seanjc, kvm, linux-kernel, roypat, kalyazin, Fuad Tabba,
Vishal Annapurve, david
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!
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [ANNOUNCE] PUCK Agenda - 2025.04.02 - No Topic
2025-04-29 14:49 ` Ackerley Tng
@ 2025-04-29 16:47 ` Sean Christopherson
2025-05-01 18:07 ` Ackerley Tng
0 siblings, 1 reply; 4+ messages in thread
From: Sean Christopherson @ 2025-04-29 16:47 UTC (permalink / raw)
To: Ackerley Tng
Cc: kvm, linux-kernel, roypat, kalyazin, Fuad Tabba, Vishal Annapurve,
david
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).
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [ANNOUNCE] PUCK Agenda - 2025.04.02 - No Topic
2025-04-29 16:47 ` Sean Christopherson
@ 2025-05-01 18:07 ` Ackerley Tng
0 siblings, 0 replies; 4+ messages in thread
From: Ackerley Tng @ 2025-05-01 18:07 UTC (permalink / raw)
To: Sean Christopherson
Cc: kvm, linux-kernel, roypat, kalyazin, Fuad Tabba, Vishal Annapurve,
david
Sean Christopherson <seanjc@google.com> writes:
> 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).
We managed to get it discussed at the guest_memfd upstream call. Here are
the slides, updated with discussion notes:
https://lpc.events/event/18/contributions/1764/attachments/1409/3708/2025-05-01-kvm-memory-attributes-vs-guest_memfd-shareability.pdf
Please remove the topic from the next PUCK! Thanks.
^ permalink raw reply [flat|nested] 4+ messages in thread
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2025-04-02 0:29 [ANNOUNCE] PUCK Agenda - 2025.04.02 - No Topic Sean Christopherson
2025-04-29 14:49 ` Ackerley Tng
2025-04-29 16:47 ` Sean Christopherson
2025-05-01 18:07 ` Ackerley Tng
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