This patchset is also available at: https://github.com/amdese/linux/commits/snp-guest-req-v2 and is based on top of kvm-coco-queue (ace0c64d8975): https://git.kernel.org/pub/scm/virt/kvm/kvm.git/log/?h=kvm-coco-queue As discussed on the PUCK call a few weeks backs, I'm re-submitting as a separate patchset the SNP guest request support that was originally part of the SNP KVM base support patchset that's now in kvm/next and will be in kernel 6.11. This support is needed to ensure fully compliance with GHCB 2.0 specification and to support attestation in general, so I'm hoping it can also make it into 6.11. I've dropped patches 4-5 from v1 of this series that implemented KVM_EXIT_COCO and handling for userspace-provided certificate data so that there's more time to get the API ironed out. Overview -------- The GHCB 2.0 specification defines 2 GHCB request types to allow SNP guests to send encrypted messages/requests to firmware: SNP Guest Requests and SNP Extended Guest Requests. These encrypted messages are used for things like servicing attestation requests issued by the guest. Implementing support for these is required to be fully GHCB-compliant. For the most part, KVM only needs to handle forwarding these requests to firmware (to be issued via the SNP_GUEST_REQUEST firmware command defined in the SEV-SNP Firmware ABI), and then forwarding the encrypted response to the guest. However, in the case of SNP Extended Guest Requests, the host is also able to provide the certificate data corresponding to the endorsement key used by firmware to sign attestation report requests. This certificate data is provided by userspace because: 1) It allows for different keys/key types to be used for each particular guest with requiring any sort of KVM API to configure the certificate table in advance on a per-guest basis. 2) It provides additional flexibility with how attestation requests might be handled during live migration where the certificate data for source/dest might be different. 3) It allows all synchronization between certificates and firmware/signing key updates to be handled purely by userspace rather than requiring some in-kernel mechanism to facilitate it. [1] To support fetching certificate data from userspace, a new KVM exit type will be needed to handle fetching the certificate from userspace. An attempt to define a new KVM_EXIT_COCO/KVM_EXIT_COCO_REQ_CERTS exit type to handle this was introduced in v1 of this patchset, but is still being discussed by community, so for now this patchset only implements a stub version of SNP Extended Guest Requests that does not provide certificate data, but is still enough to provide compliance with the GHCB 2.0 spec. [1] https://lore.kernel.org/kvm/ZS614OSoritrE1d2@xxxxxxxxxx/ Any feedback/review is appreciated. Thanks! -Mike Changes since v1: * Fix cleanup path when handling firmware error (Liam, Sean) * Use bounce-pages for interacting with firmware rather than passing in the guest-provided pages directly. (Sean) * Drop SNP_GUEST_VMM_ERR_GENERIC and rely solely on firmware-provided error code to report any firmware error to the guest. (Sean) * Use kvm_clear_guest() to handle writing empty certificate table instead of kvm_write_guest() (Sean) * Add additional comments in commit messages and throughout code to better explain the interactions with firmware/guest. (Sean) * Drop 4K-alignment restrictions on the guest-provided req/resp buffers, since the GHCB-spec only specifically requires they fit within 4K, not necessarily that they be 4K-aligned. Additionally, the bounce pages passed to firmware will be 4K-aligned regardless. Changes since splitting this off from v15 SNP KVM patchset: * Address clang-reported warnings regarding uninitialized variables * Address a memory leak of the request/response buffer pages, and refactor the code based on Sean's suggestions: https://lore.kernel.org/kvm/ZktbBRLXeOp9X6aH@xxxxxxxxxx/ * Fix SNP Extended Guest Request handling to only attempt to fetch certificates if handling MSG_REQ_REPORT (attestation) message types * Drop KVM_EXIT_VMGEXIT and introduce KVM_EXIT_COCO events instead * Refactor patch layout for easier handling/review ---------------------------------------------------------------- Brijesh Singh (1): KVM: SEV: Provide support for SNP_GUEST_REQUEST NAE event Michael Roth (2): x86/sev: Move sev_guest.h into common SEV header KVM: SEV: Provide support for SNP_EXTENDED_GUEST_REQUEST NAE event arch/x86/include/asm/sev.h | 48 ++++++++ arch/x86/kvm/svm/sev.c | 187 ++++++++++++++++++++++++++++++++ arch/x86/kvm/svm/svm.h | 3 + drivers/virt/coco/sev-guest/sev-guest.c | 2 - drivers/virt/coco/sev-guest/sev-guest.h | 63 ----------- include/uapi/linux/sev-guest.h | 3 + 6 files changed, 241 insertions(+), 65 deletions(-) delete mode 100644 drivers/virt/coco/sev-guest/sev-guest.h
