linux-kernel - Re: [PATCH v2 00/14] KVM: guest_memfd: lazy preparation of pages + prefault support for SEV-SNP

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Message-ID: <20240729220638.s7r4ibv5gln6h74u@amd.com>
Date: Mon, 29 Jul 2024 17:06:38 -0500
From: Michael Roth <michael.roth@....com>
To: Paolo Bonzini <pbonzini@...hat.com>
CC: <linux-kernel@...r.kernel.org>, <kvm@...r.kernel.org>,
	<seanjc@...gle.com>, <pratikrajesh.sampat@....com>
Subject: Re: [PATCH v2 00/14] KVM: guest_memfd: lazy preparation of pages +
 prefault support for SEV-SNP

On Fri, Jul 26, 2024 at 02:51:43PM -0400, Paolo Bonzini wrote:
> Paolo Bonzini (14):
>   KVM: x86: disallow pre-fault for SNP VMs before initialization
>   KVM: guest_memfd: return folio from __kvm_gmem_get_pfn()
>   KVM: guest_memfd: delay folio_mark_uptodate() until after successful
>     preparation
>   KVM: guest_memfd: do not go through struct page
>   KVM: rename CONFIG_HAVE_KVM_GMEM_* to CONFIG_HAVE_KVM_ARCH_GMEM_*
>   KVM: guest_memfd: return locked folio from __kvm_gmem_get_pfn
>   KVM: guest_memfd: delay kvm_gmem_prepare_folio() until the memory is
>     passed to the guest
>   KVM: guest_memfd: make kvm_gmem_prepare_folio() operate on a single
>     struct kvm
>   KVM: remove kvm_arch_gmem_prepare_needed()
>   KVM: guest_memfd: move check for already-populated page to common code
>   KVM: cleanup and add shortcuts to kvm_range_has_memory_attributes()
>   KVM: extend kvm_range_has_memory_attributes() to check subset of
>     attributes
>   KVM: guest_memfd: let kvm_gmem_populate() operate only on private gfns
>   KVM: guest_memfd: abstract how prepared folios are recorded

Re-tested series with multiple SNP guests with/without experimental THP
patches on top.

Also re-tested using the following SNP self tests (I believe Pratik has
a newer version he'll be submitting soon):

  https://github.com/mdroth/linux/commits/snp-uptodate2-kst4/
  x86_64/coco_pre_fault_memory_test

Series:

Tested-by: Michael Roth <michael.roth@....com>

> 
> v1->v2:
> - patch 1: new
> - patch 7: point out benign race between page fault and hole-punch
> - patch 7: clean up comments
> - patch 10: clean up commit message
> - patch 11: remove ";;"
> - patch 13: fix length argument to kvm_range_has_memory_attributes()
> - patch 14: new
> 
>  Documentation/virt/kvm/api.rst  |   6 +
>  arch/x86/include/asm/kvm_host.h |   1 +
>  arch/x86/kvm/Kconfig            |   4 +-
>  arch/x86/kvm/mmu/mmu.c          |   5 +-
>  arch/x86/kvm/svm/sev.c          |  17 +--
>  arch/x86/kvm/svm/svm.c          |   1 +
>  arch/x86/kvm/x86.c              |  12 +-
>  include/linux/kvm_host.h        |   9 +-
>  virt/kvm/Kconfig                |   4 +-
>  virt/kvm/guest_memfd.c          | 226 +++++++++++++++++++-------------
>  virt/kvm/kvm_main.c             |  73 +++++------
>  11 files changed, 206 insertions(+), 152 deletions(-)
> 
> -- 
> 2.43.0
> 
>