The Arm SMCCC is rather prescriptive in regards to the allocation of SMCCC function ID ranges. Many of the hypercall ranges have an associated specification from Arm (FF-A, PSCI, SDEI, etc.) with some room for vendor-specific implementations. The ever-expanding SMCCC surface leaves a lot of work within KVM for providing new features. Furthermore, KVM implements its own vendor-specific ABI, with little room for other implementations (like Hyper-V, for example). Rather than cramming it all into the kernel we should provide a way for userspace to handle hypercalls. It would appear that vCPU hotplug [*] has a legitimate use case for something like this, sending PSCI calls to userspace (where they should have gone in the first place). [*] https://lore.kernel.org/kvmarm/20230203135043.409192-1-james.morse@xxxxxxx/ => We have these new hypercall bitmap registers, why not use that? The hypercall bitmap registers aren't necessarily aimed at the same problem. The bitmap registers allow a VMM to preserve the ABI the guest gets from KVM by default when migrating between hosts. By default KVM exposes the entire feature set to the guest, whereas user SMCCC calls need explicit opt-in from userspace. Applies to 6.3-rc3. Note that the kvm->lock is used in this series to guard the SMCCC filter and should be converted to use kvm->arch.config_lock when that is available. Marc, you can find my conflict resolution below between these two series, and I've also pushed the result to: git://git.kernel.org/pub/scm/linux/kernel/git/oupton/linux.git kvm-arm64/for-6.4 Presumptive, I know! :) v1: https://lore.kernel.org/kvmarm/20230320221002.4191007-1-oliver.upton@xxxxxxxxx/ v1 -> v2: - Only set bit 0 for longmode, requiring the remaining lower 31 bits be 0 (Sean) - Let errors from kvm_smccc_call_handler() reach userspace (Suzuki) - Use the kvm_vm_has_ran_once() helper in the hypercall bitmap register handlers - Collect Suzuki's R-bs (thanks!) Oliver Upton (13): KVM: x86: Redefine 'longmode' as a flag for KVM_EXIT_HYPERCALL KVM: arm64: Add a helper to check if a VM has ran once KVM: arm64: Add vm fd device attribute accessors KVM: arm64: Rename SMC/HVC call handler to reflect reality KVM: arm64: Start handling SMCs from EL1 KVM: arm64: Refactor hvc filtering to support different actions KVM: arm64: Use a maple tree to represent the SMCCC filter KVM: arm64: Add support for KVM_EXIT_HYPERCALL KVM: arm64: Indroduce support for userspace SMCCC filtering KVM: arm64: Return NOT_SUPPORTED to guest for unknown PSCI version KVM: arm64: Let errors from SMCCC emulation to reach userspace KVM: selftests: Add a helper for SMCCC calls with SMC instruction KVM: selftests: Add test for SMCCC filter Documentation/virt/kvm/api.rst | 25 ++- Documentation/virt/kvm/devices/vm.rst | 76 +++++++ arch/arm64/include/asm/kvm_host.h | 8 +- arch/arm64/include/uapi/asm/kvm.h | 24 +++ arch/arm64/kvm/arm.c | 35 ++++ arch/arm64/kvm/handle_exit.c | 36 ++-- arch/arm64/kvm/hypercalls.c | 156 +++++++++++++- arch/arm64/kvm/pmu-emul.c | 4 +- arch/arm64/kvm/psci.c | 7 +- arch/x86/include/asm/kvm_host.h | 7 + arch/x86/include/uapi/asm/kvm.h | 3 + arch/x86/kvm/x86.c | 6 +- include/kvm/arm_hypercalls.h | 6 +- include/uapi/linux/kvm.h | 9 +- tools/testing/selftests/kvm/Makefile | 1 + .../selftests/kvm/aarch64/smccc_filter.c | 196 ++++++++++++++++++ .../selftests/kvm/include/aarch64/processor.h | 13 ++ .../selftests/kvm/lib/aarch64/processor.c | 52 +++-- 18 files changed, 601 insertions(+), 63 deletions(-) create mode 100644 tools/testing/selftests/kvm/aarch64/smccc_filter.c base-commit: e8d018dd0257f744ca50a729e3d042cf2ec9da65 diff --cc arch/arm64/kvm/pmu-emul.c index 82991d89c2ea,a0fc569fdbca..000000000000 --- a/arch/arm64/kvm/pmu-emul.c +++ b/arch/arm64/kvm/pmu-emul.c @@@ -959,8 -961,12 +959,8 @@@ int kvm_arm_pmu_v3_set_attr(struct kvm_ filter.action != KVM_PMU_EVENT_DENY)) return -EINVAL; - if (test_bit(KVM_ARCH_FLAG_HAS_RAN_ONCE, &kvm->arch.flags)) - mutex_lock(&kvm->lock); - - if (kvm_vm_has_ran_once(kvm)) { - mutex_unlock(&kvm->lock); ++ if (kvm_vm_has_ran_once(kvm)) return -EBUSY; - } if (!kvm->arch.pmu_filter) { kvm->arch.pmu_filter = bitmap_alloc(nr_events, GFP_KERNEL_ACCOUNT); diff --git a/arch/arm64/kvm/hypercalls.c b/arch/arm64/kvm/hypercalls.c index 28842b9d6c27..9ebfe8457299 100644 --- a/arch/arm64/kvm/hypercalls.c +++ b/arch/arm64/kvm/hypercalls.c @@ -154,7 +154,7 @@ static int kvm_smccc_set_filter(struct kvm *kvm, struct kvm_smccc_filter __user if (copy_from_user(&filter, uaddr, sizeof(filter))) return -EFAULT; - mutex_lock(&kvm->lock); + mutex_lock(&kvm->arch.config_lock); if (kvm_vm_has_ran_once(kvm)) { r = -EBUSY; @@ -177,7 +177,7 @@ static int kvm_smccc_set_filter(struct kvm *kvm, struct kvm_smccc_filter __user set_bit(KVM_ARCH_FLAG_SMCCC_FILTER_CONFIGURED, &kvm->arch.flags); out_unlock: - mutex_unlock(&kvm->lock); + mutex_unlock(&kvm->arch.config_lock); return r; } -- 2.40.0.348.gf938b09366-goog
