Hi, Changes since v1 [0]: - Restrict protected VM features based on an allowed features rather than rejected ones (Drew) - Add more background describing protected KVM to the cover letter (Alex) - Rebase on the latest kvmarm/next This patch series adds support for restricting CPU features for protected VMs in KVM (pKVM) [1]. Various feature configurations are allowed in KVM/arm64. Supporting all these features in pKVM is difficult, as it either involves moving much of the handling code to EL2, which adds bloat and results in a less verifiable trusted code base. Or it involves leaving the code handling at EL1, which risks having an untrusted host kernel feeding wrong information to the EL2 and to the protected guests. This series attempts to mitigate this by reducing the configuration space, providing a reduced amount of feature support at EL2 with the least amount of compromise of protected guests' capabilities. This is done by restricting CPU features exposed to protected guests through feature registers. These restrictions are enforced by trapping register accesses as well as instructions associated with these features, and injecting an undefined exception into the guest if it attempts to use a restricted feature. The features being restricted (only for protected VMs in protected mode) are the following: - Debug, Trace, and DoubleLock - Performance Monitoring (PMU) - Statistical Profiling (SPE) - Scalable Vector Extension (SVE) - Memory Partitioning and Monitoring (MPAM) - Activity Monitoring (AMU) - Memory Tagging (MTE) - Limited Ordering Regions (LOR) - AArch32 State - Generic Interrupt Controller (GIC) (depending on rVIC support) - Nested Virtualization (NV) - Reliability, Availability, and Serviceability (RAS) above V1 - Implementation-defined Features Remaining features currently supported by KVM are allowed. If new hardware features become supported by KVM, they would need to be explicitly allowed for protected VMs. This series is based on kvmarm/next and Will's patches for an Initial pKVM user ABI [2]. You can find the applied series here [3]. Cheers, /fuad [0] https://lore.kernel.org/kvmarm/20210608141141.997398-1-tabba@xxxxxxxxxx/ [1] Once complete, protected KVM adds the ability to create protected VMs. These protected VMs are protected from the host Linux kernel (and from other VMs), where the host does not have access to guest memory,even if compromised. Normal (nVHE) guests can still be created and run in parallel with protected VMs. Their functionality should not be affected. For protected VMs, the host should not even have access to a protected guest's state or anything that would enable it to manipulate it (e.g., vcpu register context and el2 system registers); only hyp would have that access. If the host could access that state, then it might be able to get around the protection provided. Therefore, anything that is sensitive and that would require such access needs to happen at hyp, hence the code in nvhe running only at hyp. For more details about pKVM, please refer to Will's talk at KVM Forum 2020: https://mirrors.edge.kernel.org/pub/linux/kernel/people/will/slides/kvmforum-2020-edited.pdf https://www.youtube.com/watch?v=edqJSzsDRxk [2] https://lore.kernel.org/kvmarm/20210603183347.1695-1-will@xxxxxxxxxx/ [3] https://android-kvm.googlesource.com/linux/+/refs/heads/tabba/el2_fixed_feature_v2 Fuad Tabba (13): KVM: arm64: Remove trailing whitespace in comments KVM: arm64: MDCR_EL2 is a 64-bit register KVM: arm64: Fix names of config register fields KVM: arm64: Refactor sys_regs.h,c for nVHE reuse KVM: arm64: Restore mdcr_el2 from vcpu KVM: arm64: Add feature register flag definitions KVM: arm64: Add config register bit definitions KVM: arm64: Guest exit handlers for nVHE hyp KVM: arm64: Add trap handlers for protected VMs KVM: arm64: Move sanitized copies of CPU features KVM: arm64: Trap access to pVM restricted features KVM: arm64: Handle protected guests at 32 bits KVM: arm64: Check vcpu features at pVM creation arch/arm64/include/asm/kvm_arm.h | 53 ++- arch/arm64/include/asm/kvm_asm.h | 2 +- arch/arm64/include/asm/kvm_host.h | 2 +- arch/arm64/include/asm/kvm_hyp.h | 3 + arch/arm64/include/asm/sysreg.h | 9 + arch/arm64/kvm/arm.c | 3 + arch/arm64/kvm/debug.c | 5 +- arch/arm64/kvm/hyp/include/hyp/switch.h | 42 +++ arch/arm64/kvm/hyp/nvhe/Makefile | 2 +- arch/arm64/kvm/hyp/nvhe/debug-sr.c | 2 +- arch/arm64/kvm/hyp/nvhe/mem_protect.c | 6 - arch/arm64/kvm/hyp/nvhe/switch.c | 125 ++++++- arch/arm64/kvm/hyp/nvhe/sys_regs.c | 477 ++++++++++++++++++++++++ arch/arm64/kvm/hyp/vhe/debug-sr.c | 2 +- arch/arm64/kvm/pkvm.c | 43 +++ arch/arm64/kvm/sys_regs.c | 34 +- arch/arm64/kvm/sys_regs.h | 35 ++ 17 files changed, 784 insertions(+), 61 deletions(-) create mode 100644 arch/arm64/kvm/hyp/nvhe/sys_regs.c base-commit: bc63d9369b320fd3c85ee13a029af9dc0ddac0ea -- 2.32.0.272.g935e593368-goog
