On Mon, Apr 5, 2021 at 7:20 AM Ashish Kalra <Ashish.Kalra@xxxxxxx> wrote: > > From: Ashish Kalra <ashish.kalra@xxxxxxx> > > The series add support for AMD SEV guest live migration commands. To protect the > confidentiality of an SEV protected guest memory while in transit we need to > use the SEV commands defined in SEV API spec [1]. > > SEV guest VMs have the concept of private and shared memory. Private memory > is encrypted with the guest-specific key, while shared memory may be encrypted > with hypervisor key. The commands provided by the SEV FW are meant to be used > for the private memory only. The patch series introduces a new hypercall. > The guest OS can use this hypercall to notify the page encryption status. > If the page is encrypted with guest specific-key then we use SEV command during > the migration. If page is not encrypted then fallback to default. > > The patch adds new KVM_EXIT_DMA_SHARE/KVM_EXIT_DMA_UNSHARE hypercall to > userspace exit functionality as a common interface from the guest back to the > VMM and passing on the guest shared/unencrypted page information to the > userspace VMM/Qemu. Qemu can consult this information during migration to know > whether the page is encrypted. > > This section descibes how the SEV live migration feature is negotiated > between the host and guest, the host indicates this feature support via > KVM_FEATURE_CPUID. The guest firmware (OVMF) detects this feature and > sets a UEFI enviroment variable indicating OVMF support for live > migration, the guest kernel also detects the host support for this > feature via cpuid and in case of an EFI boot verifies if OVMF also > supports this feature by getting the UEFI enviroment variable and if it > set then enables live migration feature on host by writing to a custom > MSR, if not booted under EFI, then it simply enables the feature by > again writing to the custom MSR. The MSR is also handled by the > userspace VMM/Qemu. > > A branch containing these patches is available here: > https://github.com/AMDESE/linux/tree/sev-migration-v11 > > [1] https://developer.amd.com/wp-content/resources/55766.PDF > > Changes since v10: > - Adds new KVM_EXIT_DMA_SHARE/KVM_EXIT_DMA_UNSHARE hypercall to > userspace exit functionality as a common interface from the guest back to the > KVM and passing on the guest shared/unencrypted region information to the > userspace VMM/Qemu. KVM/host kernel does not maintain the guest shared > memory regions information anymore. > - Remove implicit enabling of SEV live migration feature for an SEV > guest, now this is explicitly in control of the userspace VMM/Qemu. > - Custom MSR handling is also now moved into userspace VMM/Qemu. > - As KVM does not maintain the guest shared memory region information > anymore, sev_dbg_crypt() cannot bypass unencrypted guest memory > regions without support from userspace VMM/Qemu. > > Changes since v9: > - Transitioning from page encryption bitmap to the shared pages list > to keep track of guest's shared/unencrypted memory regions. > - Move back to marking the complete _bss_decrypted section as > decrypted in the shared pages list. > - Invoke a new function check_kvm_sev_migration() via kvm_init_platform() > for guest to query for host-side support for SEV live migration > and to enable the SEV live migration feature, to avoid > #ifdefs in code > - Rename MSR_KVM_SEV_LIVE_MIG_EN to MSR_KVM_SEV_LIVE_MIGRATION. > - Invoke a new function handle_unencrypted_region() from > sev_dbg_crypt() to bypass unencrypted guest memory regions. > > Changes since v8: > - Rebasing to kvm next branch. > - Fixed and added comments as per review feedback on v8 patches. > - Removed implicitly enabling live migration for incoming VMs in > in KVM_SET_PAGE_ENC_BITMAP, it is now done via KVM_SET_MSR ioctl. > - Adds support for bypassing unencrypted guest memory regions for > DBG_DECRYPT API calls, guest memory region encryption status in > sev_dbg_decrypt() is referenced using the page encryption bitmap. > > Changes since v7: > - Removed the hypervisor specific hypercall/paravirt callback for > SEV live migration and moved back to calling kvm_sev_hypercall3 > directly. > - Fix build errors as > Reported-by: kbuild test robot <lkp@xxxxxxxxx>, specifically fixed > build error when CONFIG_HYPERVISOR_GUEST=y and > CONFIG_AMD_MEM_ENCRYPT=n. > - Implicitly enabled live migration for incoming VM(s) to handle > A->B->C->... VM migrations. > - Fixed Documentation as per comments on v6 patches. > - Fixed error return path in sev_send_update_data() as per comments > on v6 patches. > > Changes since v6: > - Rebasing to mainline and refactoring to the new split SVM > infrastructre. > - Move to static allocation of the unified Page Encryption bitmap > instead of the dynamic resizing of the bitmap, the static allocation > is done implicitly by extending kvm_arch_commit_memory_region() callack > to add svm specific x86_ops which can read the userspace provided memory > region/memslots and calculate the amount of guest RAM managed by the KVM > and grow the bitmap. > - Fixed KVM_SET_PAGE_ENC_BITMAP ioctl to set the whole bitmap instead > of simply clearing specific bits. > - Removed KVM_PAGE_ENC_BITMAP_RESET ioctl, which is now performed using > KVM_SET_PAGE_ENC_BITMAP. > - Extended guest support for enabling Live Migration feature by adding a > check for UEFI environment variable indicating OVMF support for Live > Migration feature and additionally checking for KVM capability for the > same feature. If not booted under EFI, then we simply check for KVM > capability. > - Add hypervisor specific hypercall for SEV live migration by adding > a new paravirt callback as part of x86_hyper_runtime. > (x86 hypervisor specific runtime callbacks) > - Moving MSR handling for MSR_KVM_SEV_LIVE_MIG_EN into svm/sev code > and adding check for SEV live migration enabled by guest in the > KVM_GET_PAGE_ENC_BITMAP ioctl. > - Instead of the complete __bss_decrypted section, only specific variables > such as hv_clock_boot and wall_clock are marked as decrypted in the > page encryption bitmap > > Changes since v5: > - Fix build errors as > Reported-by: kbuild test robot <lkp@xxxxxxxxx> > > Changes since v4: > - Host support has been added to extend KVM capabilities/feature bits to > include a new KVM_FEATURE_SEV_LIVE_MIGRATION, which the guest can > query for host-side support for SEV live migration and a new custom MSR > MSR_KVM_SEV_LIVE_MIG_EN is added for guest to enable the SEV live > migration feature. > - Ensure that _bss_decrypted section is marked as decrypted in the > page encryption bitmap. > - Fixing KVM_GET_PAGE_ENC_BITMAP ioctl to return the correct bitmap > as per the number of pages being requested by the user. Ensure that > we only copy bmap->num_pages bytes in the userspace buffer, if > bmap->num_pages is not byte aligned we read the trailing bits > from the userspace and copy those bits as is. This fixes guest > page(s) corruption issues observed after migration completion. > - Add kexec support for SEV Live Migration to reset the host's > page encryption bitmap related to kernel specific page encryption > status settings before we load a new kernel by kexec. We cannot > reset the complete page encryption bitmap here as we need to > retain the UEFI/OVMF firmware specific settings. > > Changes since v3: > - Rebasing to mainline and testing. > - Adding a new KVM_PAGE_ENC_BITMAP_RESET ioctl, which resets the > page encryption bitmap on a guest reboot event. > - Adding a more reliable sanity check for GPA range being passed to > the hypercall to ensure that guest MMIO ranges are also marked > in the page encryption bitmap. > > Changes since v2: > - reset the page encryption bitmap on vcpu reboot > > Changes since v1: > - Add support to share the page encryption between the source and target > machine. > - Fix review feedbacks from Tom Lendacky. > - Add check to limit the session blob length. > - Update KVM_GET_PAGE_ENC_BITMAP icotl to use the base_gfn instead of > the memory slot when querying the bitmap. > > Ashish Kalra (5): > KVM: X86: Introduce KVM_HC_PAGE_ENC_STATUS hypercall > KVM: x86: Introduce new KVM_FEATURE_SEV_LIVE_MIGRATION feature & > Custom MSR. > EFI: Introduce the new AMD Memory Encryption GUID. > x86/kvm: Add guest support for detecting and enabling SEV Live > Migration feature. > x86/kvm: Add kexec support for SEV Live Migration. > > Brijesh Singh (8): > KVM: SVM: Add KVM_SEV SEND_START command > KVM: SVM: Add KVM_SEND_UPDATE_DATA command > KVM: SVM: Add KVM_SEV_SEND_FINISH command > KVM: SVM: Add support for KVM_SEV_RECEIVE_START command > KVM: SVM: Add KVM_SEV_RECEIVE_UPDATE_DATA command > KVM: SVM: Add KVM_SEV_RECEIVE_FINISH command > KVM: x86: Add AMD SEV specific Hypercall3 > mm: x86: Invoke hypercall when page encryption status is changed > > .../virt/kvm/amd-memory-encryption.rst | 120 ++++ > Documentation/virt/kvm/api.rst | 18 + > Documentation/virt/kvm/cpuid.rst | 5 + > Documentation/virt/kvm/hypercalls.rst | 15 + > Documentation/virt/kvm/msr.rst | 12 + > arch/x86/include/asm/kvm_host.h | 2 + > arch/x86/include/asm/kvm_para.h | 12 + > arch/x86/include/asm/mem_encrypt.h | 8 + > arch/x86/include/asm/paravirt.h | 10 + > arch/x86/include/asm/paravirt_types.h | 2 + > arch/x86/include/uapi/asm/kvm_para.h | 4 + > arch/x86/kernel/kvm.c | 76 +++ > arch/x86/kernel/paravirt.c | 1 + > arch/x86/kvm/cpuid.c | 3 +- > arch/x86/kvm/svm/sev.c | 514 ++++++++++++++++++ > arch/x86/kvm/svm/svm.c | 24 + > arch/x86/kvm/svm/svm.h | 2 + > arch/x86/kvm/vmx/vmx.c | 1 + > arch/x86/kvm/x86.c | 12 + > arch/x86/mm/mem_encrypt.c | 98 +++- > arch/x86/mm/pat/set_memory.c | 7 + > include/linux/efi.h | 1 + > include/linux/psp-sev.h | 8 +- > include/uapi/linux/kvm.h | 47 ++ > include/uapi/linux/kvm_para.h | 1 + > 25 files changed, 997 insertions(+), 6 deletions(-) > > -- > 2.17.1 > Overall, these patches are in pretty good shape. I have some nits, but otherwise these seem good to go.
