This patchset is also available at: https://github.com/amdese/linux/commits/snp-host-v9-rfc and is based on top of the following tree: https://github.com/mdroth/linux/commits/kvm_gmem_solo_fixes which in turn is based on Sean Christopherson's UPM base support tree, with a couple fixes/workarounds needed for SEV/SNP support. [1] == OVERVIEW == This patchset implements SEV-SNP hypervisor support for linux. This version is being posted as an RFC due to fairly extensive changes relating to transitioning the SEV-SNP implementation to using guest_memfd (gmem, aka Unmapped Private Memory) to manage private guest pages instead of the legacy SEV memory registration ioctls. For this purpose we've added a number of hooks on top of gmem to plumb in necessary RMP table updates corresponding when mapping private memory into a guest's nested page table, and then restoring it to shared/hypervisor-owned state we free'ing gmem-allocated memory back to the host. Our hope is that some of these hooks can be re-used for other platforms as well, but have tried to make them as minimal as possible if they prove to be SNP-specific. For quicker review of this aspect, they are at the beginning of the series, directly on top of the gmem patchset. Outside of UPM-related items, we've also included fairly extensive changes based on review feedback from v8 and would appreciate any feedback on those aspects as well. == LAYOUT == PATCH 01-05: Pre-patches that add generic gmem and KVM MMU hooks to handle plumbing gmem memory into CoCo guests, and make arch/x86/coco re-usability for common SEV host code instead of only guest code.. PATCH 06-22: Host SNP initialization code and CCP driver prep for handling SNP cmds PATCH 13-22: general SNP detection/enablement for host and CCP driver PATCH 23-46: core KVM support for running SEV-SNP guests PATCH 47-51: misc handling for IOMMU support, guest request handling, and debug infrastructure == TESTING (note updated QEMU command-lines) == For testing this via QEMU, use the following tree: https://github.com/amdese/qemu/commits/snp-wip-gmem SEV-SNP with gmem/UPM enabled: # set discard=none to disable discarding memory post-conversion, faster # boot times, but increased memory usage qemu-system-x86_64 -cpu EPYC-Milan-v2 \ -object memory-backend-memfd-private,id=ram1,size=1G,share=true \ -object sev-snp-guest,id=sev0,cbitpos=51,reduced-phys-bits=1,discard=both \ -machine q35,confidential-guest-support=sev0,memory-backend=ram1,kvm-type=protected \ ... KVM selftests for UPM: cd $kernel_src_dir make -C tools/testing/selftests TARGETS="kvm" EXTRA_CFLAGS="-DDEBUG -I<path to kernel headers>" sudo tools/testing/selftests/kvm/x86_64/private_mem_conversions_test == BACKGROUND (SEV-SNP) == This part of the Secure Encrypted Paging (SEV-SNP) series focuses on the changes required in a host OS for SEV-SNP support. The series builds upon SEV-SNP Guest Support now part of mainline. This 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. The CCP driver is enhanced to provide new APIs that use the SEV-SNP specific commands defined in the SEV-SNP firmware specification. The KVM driver uses those APIs to create and managed the SEV-SNP guests. The GHCB specification version 2 introduces new set of NAE's that is used by the SEV-SNP guest to communicate with the hypervisor. The series provides support to handle the following new NAE events: - Register GHCB GPA - Page State Change Request - Hypevisor feature - Guest message request 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 outisde 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 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 added 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. == TODO / KNOWN ISSUES == * Add a per-arch CONFIG option for enabling platform-specific handling when invalidating gmem pages and free'ing the back to host, as opposed to the current approach which defaults to issuing invalidations to a weak-referenced stub implementation for non-x86 builds. Hoping for more feedback on general implementation first. * This should incorporate all review feedback from v8, but if anything slipped through the cracks please let me know. [1] https://lore.kernel.org/lkml/20230512002124.3sap3kzxpegwj3n2@xxxxxxx/ Changes since v8: * Rework gmem/UPM hooks based on Sean's latest gmem/UPM tree * Move SEV lazy-pinning support out to a separate series which uses this series as a prereq instead of the other way around. * Re-organize extended guest request patches into 3 patches encompassing SEV FD ioctls for host-wide certs, KVM ioctls for per-instance certs, and the guest request handling that consumes them. Also move them to the top of the series to better separate them for the core SNP patches (Alexey, Zhi, Ashish, Dov, Dionna, others) * Various other changes/fixups for extended guests request handling (Dov, Alexey, Dionna) * Use helper to calculate max RMP entry size and improve readability (Dave) * Use architecture-independent GPA value for initial VMSA pages * Ensure SEV_CMD_SNP_GUEST_REQUEST failures are indicated to guest (Alex) * Allocate per-instance certs on-demand (Alex) * comment fixup for RMP fault handling (Zhi) * commit msg rewording for MSR-based PSCs (Zhi) * update SNP command/struct definitions based on 1.54 ABI (Saban) * use sev_deactivate_lock around SEV_CMD_SNP_DECOMMISSION (Saban) * Various comment/commit fixups (Zhi, Alex, Kim, Vlastimil, Dave, * kexec fixes for newer SNP firmwares (Ashish) * Various other fixups and re-ordering of patches. Changes since v7: * Rebase to Sean's updated UPM base support tree * Drop KVM_CAP_UNMAPPED_MEMORY and .private_mem_enabled x86 op in favor of kvm_arch_has_private_mem() and vm_type KVM_VM_CREATE arg * Drop GHCB map/unmap refactoring and post map/unmap hooks as they are no longer needed with UPM * Move .fault_is_private implementation to SNP patch range, no longer needed for SEV. * Don't call attribute update / invalidation hooks under kvm->mmu_lock (Tom, Jarkko) * Revert switch to using set_memory_p()/set_memory_np() in rmpupdate() due to it causing performance regression * Commit fixups for 'fault_is_private'/'update_mem_attr' hooks, have 'fault_is_private' return bool (Boris) * Split kvm_vm_set_region_attr() into separate patch. (Jarkko) * Copy corrected CPUID page to userspace when firmware rejects it (Tom, Jarkko) * Fix sev_dump_rmpentry() error-handling (Alper) * Use adjusted cmd_buf pointer rather than sev->cmd_buf directly (Alper) * Correct typo in SNP_GET_EXT_CONFIG documentation (Dov) * Update struct kvm_sev_snp_launch_finish definition in amd-memory-encryption.rst (Tom) * Fix snp_launch_update_vmsa replacing created_vcpus with online_vcpus * Fix SNP_DBG_DECRYPT to not include len parameter. * Fix SNP_LAUNCH_FINISH to copy host-data from userspace Changes since v6: * Added support for restrictedmem/UPM, and removed SEV-specific implementation of private memory management. As a result of this rework the following patches were no longer needed so were dropped: - KVM: SVM: Mark the private vma unmergable for SEV-SNP guests - KVM: SVM: Disallow registering memory range from HugeTLB for SNP guest - KVM: x86/mmu: Introduce kvm_mmu_map_tdp_page() for use by TDX and SNP - KVM: x86: Introduce kvm_mmu_get_tdp_walk() for SEV-SNP use * Moved RMP table entry structure definition (struct rmpentry) to sev.c, to not expose this non-architectural definition to rest of the kernel and making the structure private to SNP code. Also made RMP table entry accessors to be inline functions and removed all accessors which are not called more than once. Added a new function rmptable_entry() to index into the RMP table and return RMP table entry. * Moved RMPUPDATE, PSMASH helper function declerations to x86 arch specific include namespace from linux namespace. Added comments for these helper functions. * Introduce set_memory_p() to provide a way to change atributes of a memory range to be marked as present and added to the kernel directmap, and invalidating/restoring pages from directmap are now done using set_memory_np() and set_memory_p(). * Added detailed comments around user RMP #PF fault handling and simplified computation of the faulting pfn for large-pages. * Added support to return pfn from dump_pagetable() to do SEV-specific fault handling, this is added a pre-patch. This support is now used to dump RMP entry in case of RMP #PF in show_fault_oops(). * Added a new generic SNP command params structure sev_data_snp_addr, which is used for all SNP firmware API commands requiring a single physical address parameter. * Added support for new SNP_INIT_EX command with support for HV-Fixed page range list. * Added support for new SNP_SHUTDOWN_EX command which allows disabling enforcement of SNP in the IOMMU. Also DF_FLUSH is done at SNP shutdown if it indicates DF_FLUSH is required. * Make sev_do_cmd() a generic API interface for the hypervisor to issue commands to manage an SEV and SNP guest. Also removed the API wrappers used by the hypervisor to manage an SEV-SNP guest. All these APIs now invoke sev_do_cmd() directly. * Introduce snp leaked pages list. If pages are unsafe to be released back to the page-allocator as they can't be reclaimed or transitioned back to hypervisor/shared state are now added to this internal leaked pages list to prevent fatal page faults when accessing these pages. The function snp_leak_pages() is renamed to snp_mark_pages_offline() and is an external function available to both CCP driver and the SNP hypervisor code. Removed call to memory_failure() when leaking/marking pages offline. * Remove snp_set_rmp_state() multiplexor code and add new separate helpers such as rmp_mark_pages_firmware() & rmp_mark_pages_shared(). The callers now issue snp_reclaim_pages() directly when needed as done by __snp_free_firmware_pages() and unmap_firmware_writeable(). All callers of snp_set_rmp_state() modified to call helpers rmp_mark_pages_firmware() or rmp_mark_pages_shared() as required. * Change snp_reclaim_pages() to take physical address as an argument and clear C-bit from this physical address argument internally. * Output parameter sev_user_data_ext_snp_config in sev_ioctl_snp_get_config() is memset to zero to avoid kernel memory leaking. * Prevent race between sev_ioctl_snp_set_config() and snp_guest_ext_guest_request() for sev->snp_certs_data by acquiring sev->snp_certs_lock mutex. * Zeroed out struct sev_user_data_snp_config in sev_ioctl_snp_set_config() to prevent leaking uninitialized kernel memory. * Optimized snp_safe_alloc_page() by avoiding multiple calls to pfn_to_page() and checking for a hugepage using pfn instead of expanding to full physical address. * Invoke host_rmp_make_shared() with leak parameter set to true if VMSA page cannot be transitioned back to shared state. * Fix snp_launch_finish() to always sent the ID_AUTH struct to the firmware. Use params.auth_key_en indicator to set if the ID_AUTH struct contains an author key or not. * Cleanup snp_context_create() and allocate certs_data in this function using kzalloc() to prevent giving the guest uninitialized kernel memory. * Remove the check for guest supplied buffer greater than the data provided by the hypervisor in snp_handle_ext_guest_request(). * Add check in sev_snp_ap_create() if a malicious guest can RMPADJUST a large page into VMSA which will hit the SNP erratum where the CPU will incorrectly signal an RMP violation #PF if a hugepage collides with the RMP entry of VMSA page, reject the AP CREATE request if VMSA address from guest is 2M aligned. * Make VMSAVE target area memory allocation SNP safe, implemented workaround for an SNP erratum where the CPU will incorrectly signal an RMP violation #PF if a hugepage (2mb or 1gb) collides with the RMP entry of the VMSAVE target page. * Fix handle_split_page_fault() to work with memfd backed pages. * Add KVM commands for per-VM instance certificates. * Add IOMMU_SNP_SHUTDOWN support, this adds support for Host kexec support with SNP. Documentation/virt/coco/sev-guest.rst | 54 + Documentation/virt/kvm/api.rst | 34 + .../virt/kvm/x86/amd-memory-encryption.rst | 147 ++ arch/x86/Kbuild | 2 +- arch/x86/coco/Makefile | 3 +- arch/x86/coco/sev/Makefile | 3 + arch/x86/coco/sev/host.c | 524 ++++++ arch/x86/include/asm/cpufeatures.h | 1 + arch/x86/include/asm/disabled-features.h | 8 +- arch/x86/include/asm/kvm-x86-ops.h | 3 + arch/x86/include/asm/kvm_host.h | 23 + arch/x86/include/asm/msr-index.h | 11 +- arch/x86/include/asm/sev-common.h | 30 + arch/x86/include/asm/sev-host.h | 37 + arch/x86/include/asm/sev.h | 5 +- arch/x86/include/asm/svm.h | 6 + arch/x86/include/asm/trap_pf.h | 18 +- arch/x86/kernel/cpu/amd.c | 24 +- arch/x86/kernel/cpu/bugs.c | 7 +- arch/x86/kvm/Kconfig | 1 + arch/x86/kvm/lapic.c | 5 +- arch/x86/kvm/mmu.h | 2 - arch/x86/kvm/mmu/mmu.c | 15 +- arch/x86/kvm/mmu/mmu_internal.h | 39 +- arch/x86/kvm/svm/nested.c | 2 +- arch/x86/kvm/svm/sev.c | 1802 +++++++++++++++++--- arch/x86/kvm/svm/svm.c | 53 +- arch/x86/kvm/svm/svm.h | 38 +- arch/x86/kvm/x86.c | 17 + arch/x86/mm/fault.c | 21 + drivers/crypto/ccp/sev-dev.c | 1064 +++++++++++- drivers/crypto/ccp/sev-dev.h | 16 + drivers/iommu/amd/init.c | 57 +- include/linux/amd-iommu.h | 3 +- include/linux/kvm_host.h | 10 + include/linux/psp-sev.h | 304 +++- include/uapi/linux/kvm.h | 74 + include/uapi/linux/psp-sev.h | 71 + tools/arch/x86/include/asm/cpufeatures.h | 1 + virt/kvm/guest_mem.c | 48 +- virt/kvm/kvm_main.c | 75 +- 41 files changed, 4383 insertions(+), 275 deletions(-)
