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SubjectRe: [PATCH v13 00/26] Add AMD Secure Nested Paging (SEV-SNP) Hypervisor Support
On Thu, Apr 18, 2024 at 9:42 PM Michael Roth <michael.roth@amd.com> wrote:
>
> This patchset is also available at:
>
> https://github.com/amdese/linux/commits/snp-host-v13
>
> and is based on commit 4d2deb62185f (as suggested by Paolo) from:
>
> https://git.kernel.org/pub/scm/virt/kvm/kvm.git/log/?h=kvm-coco-queue

This is pretty much ready to go into kvm-coco-queue. Let me know if
you want to do a quick v14 with the few changes I suggested, or I can
do them too.

Then the next steps are:

1) get the mm acks

2) figure out the state of patches 1-3

3) wait for more reviews of course

4) merge everything into kvm/next.

Seems in good shape for a 6.10 target.

Paolo

>
> Patch Layout
> ------------
>
> 01-03: These patches are minor dependencies for this series and are already
> included in both tip/master and mainline, so are only included here
> as a stop-gap until merged from one of those trees. These are needed
> by patch #8 in this series which makes use of CC_ATTR_HOST_SEV_SNP
>
> 04: This is a small general fix-up for guest_memfd that can be applied
> independently of this series.
>
> 05-08: These patches add some basic infrastructure and introduces a new
> KVM_X86_SNP_VM vm_type to handle differences verses the existing
> KVM_X86_SEV_VM and KVM_X86_SEV_ES_VM types.
>
> 09-11: These implement the KVM API to handle the creation of a
> cryptographic launch context, encrypt/measure the initial image
> into guest memory, and finalize it before launching it.
>
> 12-17: These implement handling for various guest-generated events such
> as page state changes, onlining of additional vCPUs, etc.
>
> 18-21: These implement the gmem hooks needed to prepare gmem-allocated
> pages before mapping them into guest private memory ranges as
> well as cleaning them up prior to returning them to the host for
> use as normal memory. Because this supplants certain activities
> like issued WBINVDs during KVM MMU invalidations, there's also
> a patch to avoid duplicating that work to avoid unecessary
> overhead.
>
> 22: With all the core support in place, the patch adds a kvm_amd module
> parameter to enable SNP support.
>
> 23-26: These patches all deal with the servicing of guest requests to handle
> things like attestation, as well as some related host-management
> interfaces.
>
>
> Testing
> -------
>
> For testing this via QEMU, use the following tree:
>
> https://github.com/amdese/qemu/commits/snp-v4-wip3
>
> A patched OVMF is also needed due to upstream KVM no longer supporting MMIO
> ranges that are mapped as private. It is recommended you build the AmdSevX64
> variant as it provides the kernel-hashing support present in this series:
>
> https://github.com/amdese/ovmf/commits/apic-mmio-fix1d
>
> A basic command-line invocation for SNP would be:
>
> qemu-system-x86_64 -smp 32,maxcpus=255 -cpu EPYC-Milan-v2
> -machine q35,confidential-guest-support=sev0,memory-backend=ram1
> -object memory-backend-memfd,id=ram1,size=4G,share=true,reserve=false
> -object sev-snp-guest,id=sev0,cbitpos=51,reduced-phys-bits=1,id-auth=
> -bios OVMF_CODE-upstream-20240410-apic-mmio-fix1d-AmdSevX64.fd
>
> With kernel-hashing and certificate data supplied:
>
> qemu-system-x86_64 -smp 32,maxcpus=255 -cpu EPYC-Milan-v2
> -machine q35,confidential-guest-support=sev0,memory-backend=ram1
> -object memory-backend-memfd,id=ram1,size=4G,share=true,reserve=false
> -object sev-snp-guest,id=sev0,cbitpos=51,reduced-phys-bits=1,id-auth=,certs-path=/home/mroth/cert.blob,kernel-hashes=on
> -bios OVMF_CODE-upstream-20240410-apic-mmio-fix1d-AmdSevX64.fd
> -kernel /boot/vmlinuz-$ver
> -initrd /boot/initrd.img-$ver
> -append "root=UUID=d72a6d1c-06cf-4b79-af43-f1bac4f620f9 ro console=ttyS0,115200n8"
>
> With standard X64 OVMF package with separate image for persistent NVRAM:
>
> qemu-system-x86_64 -smp 32,maxcpus=255 -cpu EPYC-Milan-v2
> -machine q35,confidential-guest-support=sev0,memory-backend=ram1
> -object memory-backend-memfd,id=ram1,size=4G,share=true,reserve=false
> -object sev-snp-guest,id=sev0,cbitpos=51,reduced-phys-bits=1,id-auth=
> -bios OVMF_CODE-upstream-20240410-apic-mmio-fix1d.fd
> -drive if=pflash,format=raw,unit=0,file=OVMF_VARS-upstream-20240410-apic-mmio-fix1d.fd,readonly=off
>
>
> Known issues / TODOs
> --------------------
>
> * SEV-ES guests may trigger the following warning:
>
> WARNING: CPU: 151 PID: 4003 at arch/x86/kvm/mmu/mmu.c:5855 kvm_mmu_page_fault+0x33b/0x860 [kvm]
>
> It is assumed here that these will be resolved once the transition to
> PFERR_PRIVATE_ACCESS is fully completed, but if that's not the case let me
> know and will investigate further.
>
> * Base tree in some cases reports "Unpatched return thunk in use. This should
> not happen!" the first time it runs an SVM/SEV/SNP guests. This a recent
> regression upstream and unrelated to this series:
>
> https://lore.kernel.org/linux-kernel/CANpmjNOcKzEvLHoGGeL-boWDHJobwfwyVxUqMq2kWeka3N4tXA@mail.gmail.com/T/
>
> * 2MB hugepage support has been dropped pending discussion on how we plan to
> re-enable it in gmem.
>
> * Host kexec should work, but there is a known issue with host kdump support
> while SNP guests are running that will be addressed as a follow-up.
>
> * SNP kselftests are currently a WIP and will be included as part of SNP
> upstreaming efforts in the near-term.
>
>
> SEV-SNP Overview
> ----------------
>
> This part of the Secure Encrypted Paging (SEV-SNP) series focuses on the
> changes required to add KVM support for SEV-SNP. This series builds upon
> SEV-SNP guest support, which is now in mainline, and and SEV-SNP host
> initialization support, which is now in linux-next.
>
> While series provides the basic building blocks to support booting the
> SEV-SNP VMs, it does not cover all the security enhancement introduced by
> the SEV-SNP such as interrupt protection, which will added in the future.
>
> With SNP, when pages are marked as guest-owned in the RMP table, they are
> assigned to a specific guest/ASID, as well as a specific GFN with in the
> guest. Any attempts to map it in the RMP table to a different guest/ASID,
> or a different GFN within a guest/ASID, will result in an RMP nested page
> fault.
>
> Prior to accessing a guest-owned page, the guest must validate it with a
> special PVALIDATE instruction which will set a special bit in the RMP table
> for the guest. This is the only way to set the validated bit outside of the
> initial pre-encrypted guest payload/image; any attempts outside the guest to
> modify the RMP entry from that point forward will result in the validated
> bit being cleared, at which point the guest will trigger an exception if it
> attempts to access that page so it can be made aware of possible tampering.
>
> One exception to this is the initial guest payload, which is pre-validated
> by the firmware prior to launching. The guest can use Guest Message requests
> to fetch an attestation report which will include the measurement of the
> initial image so that the guest can verify it was booted with the expected
> image/environment.
>
> After boot, guests can use Page State Change requests to switch pages
> between shared/hypervisor-owned and private/guest-owned to share data for
> things like DMA, virtio buffers, and other GHCB requests.
>
> In this implementation of SEV-SNP, private guest memory is managed by a new
> kernel framework called guest_memfd (gmem). With gmem, a new
> KVM_SET_MEMORY_ATTRIBUTES KVM ioctl has been added to tell the KVM
> MMU whether a particular GFN should be backed by shared (normal) memory or
> private (gmem-allocated) memory. To tie into this, Page State Change
> requests are forward to userspace via KVM_EXIT_VMGEXIT exits, which will
> then issue the corresponding KVM_SET_MEMORY_ATTRIBUTES call to set the
> private/shared state in the KVM MMU.
>
> The gmem / KVM MMU hooks implemented in this series will then update the RMP
> table entries for the backing PFNs to set them to guest-owned/private when
> mapping private pages into the guest via KVM MMU, or use the normal KVM MMU
> handling in the case of shared pages where the corresponding RMP table
> entries are left in the default shared/hypervisor-owned state.
>
> Feedback/review is very much appreciated!
>
> -Mike
>
>
> Changes since v12:
>
> * rebased to latest kvm-coco-queue branch (commit 4d2deb62185f)
> * add more input validation for SNP_LAUNCH_START, especially for handling
> things like MBO/MBZ policy bits, and API major/minor minimums. (Paolo)
> * block SNP KVM instances from being able to run legacy SEV commands (Paolo)
> * don't attempt to measure VMSA for vcpu 0/BSP before the others, let
> userspace deal with the ordering just like with SEV-ES (Paolo)
> * fix up docs for SNP_LAUNCH_FINISH (Paolo)
> * introduce svm->sev_es.snp_has_guest_vmsa flag to better distinguish
> handling for guest-mapped vs non-guest-mapped VMSAs, rename
> 'snp_ap_create' flag to 'snp_ap_waiting_for_reset' (Paolo)
> * drop "KVM: SEV: Use a VMSA physical address variable for populating VMCB"
> as it is no longer needed due to above VMSA rework
> * replace pr_debug_ratelimited() messages for RMP #NPFs with a single trace
> event
> * handle transient PSMASH_FAIL_INUSE return codes in kvm_gmem_invalidate(),
> switch to WARN_ON*()'s to indicate remaining error cases are not expected
> and should not be seen in practice. (Paolo)
> * add a cond_resched() in kvm_gmem_invalidate() to avoid soft lock-ups when
> cleaning up large guest memory ranges.
> * rename VLEK_REQUIRED to VCEK_DISABLE. it's be more applicable if another
> key type ever gets added.
> * don't allow attestation to be paused while an attestation request is
> being processed by firmware (Tom)
> * add missing Documentation entry for SNP_VLEK_LOAD
> * collect Reviewed-by's from Paolo and Tom
>
> Changes since v11:
>
> * Rebase series on kvm-coco-queue and re-work to leverage more
> infrastructure between SNP/TDX series.
> * Drop KVM_SNP_INIT in favor of the new KVM_SEV_INIT2 interface introduced
> here (Paolo):
> https://lore.kernel.org/lkml/20240318233352.2728327-1-pbonzini@redhat.com/
> * Drop exposure API fields related to things like VMPL levels, migration
> agents, etc., until they are actually supported/used (Sean)
> * Rework KVM_SEV_SNP_LAUNCH_UPDATE handling to use a new
> kvm_gmem_populate() interface instead of copying data directly into
> gmem-allocated pages (Sean)
> * Add support for SNP_LOAD_VLEK, rework the SNP_SET_CONFIG_{START,END} to
> have simpler semantics that are applicable to management of SNP_LOAD_VLEK
> updates as well, rename interfaces to the now more appropriate
> SNP_{PAUSE,RESUME}_ATTESTATION
> * Fix up documentation wording and do print warnings for
> userspace-triggerable failures (Peter, Sean)
> * Fix a race with AP_CREATION wake-up events (Jacob, Sean)
> * Fix a memory leak with VMSA pages (Sean)
> * Tighten up handling of RMP page faults to better distinguish between real
> and spurious cases (Tom)
> * Various patch/documentation rewording, cleanups, etc.
>
>
> ----------------------------------------------------------------
> Ashish Kalra (1):
> KVM: SEV: Avoid WBINVD for HVA-based MMU notifications for SNP
>
> Borislav Petkov (AMD) (3):
> [TEMP] x86/kvm/Kconfig: Have KVM_AMD_SEV select ARCH_HAS_CC_PLATFORM
> [TEMP] x86/cc: Add cc_platform_set/_clear() helpers
> [TEMP] x86/CPU/AMD: Track SNP host status with cc_platform_*()
>
> Brijesh Singh (10):
> KVM: SEV: Add GHCB handling for Hypervisor Feature Support requests
> KVM: SEV: Add KVM_SEV_SNP_LAUNCH_START command
> KVM: SEV: Add KVM_SEV_SNP_LAUNCH_UPDATE command
> KVM: SEV: Add KVM_SEV_SNP_LAUNCH_FINISH command
> KVM: SEV: Add support to handle GHCB GPA register VMGEXIT
> KVM: SEV: Add support to handle MSR based Page State Change VMGEXIT
> KVM: SEV: Add support to handle Page State Change VMGEXIT
> KVM: SEV: Add support to handle RMP nested page faults
> KVM: SVM: Add module parameter to enable SEV-SNP
> KVM: SEV: Provide support for SNP_GUEST_REQUEST NAE event
>
> Michael Roth (10):
> KVM: guest_memfd: Fix PTR_ERR() handling in __kvm_gmem_get_pfn()
> KVM: SEV: Select KVM_GENERIC_PRIVATE_MEM when CONFIG_KVM_AMD_SEV=y
> KVM: SEV: Add initial SEV-SNP support
> KVM: SEV: Add support for GHCB-based termination requests
> KVM: SEV: Implement gmem hook for initializing private pages
> KVM: SEV: Implement gmem hook for invalidating private pages
> KVM: x86: Implement gmem hook for determining max NPT mapping level
> crypto: ccp: Add the SNP_VLEK_LOAD command
> crypto: ccp: Add the SNP_{PAUSE,RESUME}_ATTESTATION commands
> KVM: SEV: Provide support for SNP_EXTENDED_GUEST_REQUEST NAE event
>
> Tom Lendacky (2):
> KVM: SEV: Add support to handle AP reset MSR protocol
> KVM: SEV: Support SEV-SNP AP Creation NAE event
>
> Documentation/virt/coco/sev-guest.rst | 69 +-
> Documentation/virt/kvm/api.rst | 73 +
> .../virt/kvm/x86/amd-memory-encryption.rst | 88 +-
> arch/x86/coco/core.c | 52 +
> arch/x86/include/asm/kvm_host.h | 2 +
> arch/x86/include/asm/sev-common.h | 22 +-
> arch/x86/include/asm/sev.h | 19 +-
> arch/x86/include/asm/svm.h | 9 +-
> arch/x86/include/uapi/asm/kvm.h | 39 +
> arch/x86/kernel/cpu/amd.c | 38 +-
> arch/x86/kernel/cpu/mtrr/generic.c | 2 +-
> arch/x86/kernel/sev.c | 10 -
> arch/x86/kvm/Kconfig | 4 +
> arch/x86/kvm/mmu.h | 2 -
> arch/x86/kvm/mmu/mmu.c | 1 +
> arch/x86/kvm/svm/sev.c | 1444 +++++++++++++++++++-
> arch/x86/kvm/svm/svm.c | 39 +-
> arch/x86/kvm/svm/svm.h | 50 +
> arch/x86/kvm/trace.h | 31 +
> arch/x86/kvm/x86.c | 19 +-
> arch/x86/virt/svm/sev.c | 106 +-
> drivers/crypto/ccp/sev-dev.c | 85 +-
> drivers/iommu/amd/init.c | 4 +-
> include/linux/cc_platform.h | 12 +
> include/linux/psp-sev.h | 4 +-
> include/uapi/linux/kvm.h | 28 +
> include/uapi/linux/psp-sev.h | 39 +
> include/uapi/linux/sev-guest.h | 9 +
> virt/kvm/guest_memfd.c | 8 +-
> 29 files changed, 2229 insertions(+), 79 deletions(-)
>
>


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