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SubjectRE: [PATCH v10 10/16] KVM: x86: Introduce KVM_GET_SHARED_PAGES_LIST ioctl
[AMD Public Use]

-----Original Message-----
From: Sean Christopherson <>
Sent: Tuesday, February 16, 2021 7:03 PM
To: Kalra, Ashish <>
Cc:;;;;;;; Lendacky, Thomas <>;;;;;; Singh, Brijesh <>
Subject: Re: [PATCH v10 10/16] KVM: x86: Introduce KVM_GET_SHARED_PAGES_LIST ioctl

On Thu, Feb 04, 2021, Ashish Kalra wrote:
> From: Brijesh Singh <>
> The ioctl is used to retrieve a guest's shared pages list.

>What's the performance hit to boot time if KVM_HC_PAGE_ENC_STATUS is passed through to userspace? That way, userspace could manage the set of pages >in whatever data structure they want, and these get/set ioctls go away.

What is the advantage of passing KVM_HC_PAGE_ENC_STATUS through to user-space ?

As such it is just a simple interface to get the shared page list via the get/set ioctl's. simply an array is passed to these ioctl to get/set the shared pages

>Also, aren't there plans for an in-guest migration helper? If so, do we have any idea what that interface will look like? E.g. if we're going to end up with a full >fledged driver in the guest, why not bite the bullet now and bypass KVM entirely?

Even the in-guest migration helper will be using page encryption status hypercalls, so some interface is surely required.

Also the in-guest migration will be mainly an OVMF component, won't really be a full fledged kernel driver in the guest.


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