Re: [RFC PATCH 0/8] KVM: Prepopulate guest memory API

David Matlack
2024-03-07T00:53:46Z

On 2024-03-01 09:28 AM, isaku.yamahata@intel.com wrote:
> From: Isaku Yamahata <isaku.yamahata@intel.com>
>
> Implementation:
> - x86 KVM MMU
> In x86 KVM MMU, I chose to use kvm_mmu_do_page_fault(). It's not confined to
> KVM TDP MMU. We can restrict it to KVM TDP MMU and introduce an optimized
> version.

Restricting to TDP MMU seems like a good idea. But I'm not quite sure
how to reliably do that from a vCPU context. Checking for TDP being
enabled is easy, but what if the vCPU is in guest-mode?

Perhaps we can just return an error out to userspace if the vCPU is in
guest-mode or TDP is disabled, and make it userspace's problem to do
memory mapping before loading any vCPU state.