Save and reload guest CET supervisor states, i.e.,PL{0,1,2}_SSP, when vCPU context is being swapped before and after userspace <->kernel entry, also do the same operation when vCPU is sched-in or sched-out. Enabling CET supervisor state management in KVM due to: -Introducing unnecessary XSAVE operation when switch to non-vCPU userspace within current FPU framework. -Forcing allocating additional space for CET supervisor states in each thread context regardless whether it's vCPU thread or not. Add a new helper kvm_arch_sched_out() for that purpose. Adding the support in kvm_arch_vcpu_put/load() without the new helper looks possible, but the put/load functions are also called in vcpu_put()/load(), the latter are heavily used in KVM, so adding new helper makes the implementation clearer. Signed-off-by: Yang Weijiang <weijiang.yang@xxxxxxxxx> --- arch/arm64/include/asm/kvm_host.h | 1 + arch/mips/include/asm/kvm_host.h | 1 + arch/powerpc/include/asm/kvm_host.h | 1 + arch/riscv/include/asm/kvm_host.h | 1 + arch/s390/include/asm/kvm_host.h | 1 + arch/x86/kvm/x86.c | 37 +++++++++++++++++++++++++++++ include/linux/kvm_host.h | 1 + virt/kvm/kvm_main.c | 1 + 8 files changed, 44 insertions(+) diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h index 7e7e19ef6993..98235cb3d258 100644 --- a/arch/arm64/include/asm/kvm_host.h +++ b/arch/arm64/include/asm/kvm_host.h @@ -1023,6 +1023,7 @@ void kvm_arm_vcpu_ptrauth_trap(struct kvm_vcpu *vcpu); static inline void kvm_arch_sync_events(struct kvm *kvm) {} static inline void kvm_arch_sched_in(struct kvm_vcpu *vcpu, int cpu) {} +static inline void kvm_arch_sched_out(struct kvm_vcpu *vcpu, int cpu) {} void kvm_arm_init_debug(void); void kvm_arm_vcpu_init_debug(struct kvm_vcpu *vcpu); diff --git a/arch/mips/include/asm/kvm_host.h b/arch/mips/include/asm/kvm_host.h index 957121a495f0..56c5e85ba5a3 100644 --- a/arch/mips/include/asm/kvm_host.h +++ b/arch/mips/include/asm/kvm_host.h @@ -893,6 +893,7 @@ static inline void kvm_arch_free_memslot(struct kvm *kvm, struct kvm_memory_slot *slot) {} static inline void kvm_arch_memslots_updated(struct kvm *kvm, u64 gen) {} static inline void kvm_arch_sched_in(struct kvm_vcpu *vcpu, int cpu) {} +static inline void kvm_arch_sched_out(struct kvm_vcpu *vcpu, int cpu) {} static inline void kvm_arch_vcpu_blocking(struct kvm_vcpu *vcpu) {} static inline void kvm_arch_vcpu_unblocking(struct kvm_vcpu *vcpu) {} diff --git a/arch/powerpc/include/asm/kvm_host.h b/arch/powerpc/include/asm/kvm_host.h index 14ee0dece853..11587d953bf6 100644 --- a/arch/powerpc/include/asm/kvm_host.h +++ b/arch/powerpc/include/asm/kvm_host.h @@ -880,6 +880,7 @@ static inline void kvm_arch_sync_events(struct kvm *kvm) {} static inline void kvm_arch_memslots_updated(struct kvm *kvm, u64 gen) {} static inline void kvm_arch_flush_shadow_all(struct kvm *kvm) {} static inline void kvm_arch_sched_in(struct kvm_vcpu *vcpu, int cpu) {} +static inline void kvm_arch_sched_out(struct kvm_vcpu *vcpu, int cpu) {} static inline void kvm_arch_vcpu_blocking(struct kvm_vcpu *vcpu) {} static inline void kvm_arch_vcpu_unblocking(struct kvm_vcpu *vcpu) {} diff --git a/arch/riscv/include/asm/kvm_host.h b/arch/riscv/include/asm/kvm_host.h index ee0acccb1d3b..6ff4a04fe0f2 100644 --- a/arch/riscv/include/asm/kvm_host.h +++ b/arch/riscv/include/asm/kvm_host.h @@ -244,6 +244,7 @@ struct kvm_vcpu_arch { static inline void kvm_arch_sync_events(struct kvm *kvm) {} static inline void kvm_arch_sched_in(struct kvm_vcpu *vcpu, int cpu) {} +static inline void kvm_arch_sched_out(struct kvm_vcpu *vcpu, int cpu) {} #define KVM_ARCH_WANT_MMU_NOTIFIER diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h index 2bbc3d54959d..d1750a6a86cf 100644 --- a/arch/s390/include/asm/kvm_host.h +++ b/arch/s390/include/asm/kvm_host.h @@ -1033,6 +1033,7 @@ extern int kvm_s390_gisc_unregister(struct kvm *kvm, u32 gisc); static inline void kvm_arch_sync_events(struct kvm *kvm) {} static inline void kvm_arch_sched_in(struct kvm_vcpu *vcpu, int cpu) {} +static inline void kvm_arch_sched_out(struct kvm_vcpu *vcpu, int cpu) {} static inline void kvm_arch_free_memslot(struct kvm *kvm, struct kvm_memory_slot *slot) {} static inline void kvm_arch_memslots_updated(struct kvm *kvm, u64 gen) {} diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 7a3753c05c09..f7558f0f6fc0 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -11212,6 +11212,33 @@ static void kvm_put_guest_fpu(struct kvm_vcpu *vcpu) trace_kvm_fpu(0); } +static void kvm_save_cet_supervisor_ssp(struct kvm_vcpu *vcpu) +{ + preempt_disable(); + if (unlikely(guest_can_use(vcpu, X86_FEATURE_SHSTK))) { + rdmsrl(MSR_IA32_PL0_SSP, vcpu->arch.cet_s_ssp[0]); + rdmsrl(MSR_IA32_PL1_SSP, vcpu->arch.cet_s_ssp[1]); + rdmsrl(MSR_IA32_PL2_SSP, vcpu->arch.cet_s_ssp[2]); + /* + * Omit reset to host PL{1,2}_SSP because Linux will never use + * these MSRs. + */ + wrmsrl(MSR_IA32_PL0_SSP, 0); + } + preempt_enable(); +} + +static void kvm_reload_cet_supervisor_ssp(struct kvm_vcpu *vcpu) +{ + preempt_disable(); + if (unlikely(guest_can_use(vcpu, X86_FEATURE_SHSTK))) { + wrmsrl(MSR_IA32_PL0_SSP, vcpu->arch.cet_s_ssp[0]); + wrmsrl(MSR_IA32_PL1_SSP, vcpu->arch.cet_s_ssp[1]); + wrmsrl(MSR_IA32_PL2_SSP, vcpu->arch.cet_s_ssp[2]); + } + preempt_enable(); +} + int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu) { struct kvm_queued_exception *ex = &vcpu->arch.exception; @@ -11222,6 +11249,7 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu) kvm_sigset_activate(vcpu); kvm_run->flags = 0; kvm_load_guest_fpu(vcpu); + kvm_reload_cet_supervisor_ssp(vcpu); kvm_vcpu_srcu_read_lock(vcpu); if (unlikely(vcpu->arch.mp_state == KVM_MP_STATE_UNINITIALIZED)) { @@ -11310,6 +11338,7 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu) r = vcpu_run(vcpu); out: + kvm_save_cet_supervisor_ssp(vcpu); kvm_put_guest_fpu(vcpu); if (kvm_run->kvm_valid_regs) store_regs(vcpu); @@ -12398,9 +12427,17 @@ void kvm_arch_sched_in(struct kvm_vcpu *vcpu, int cpu) pmu->need_cleanup = true; kvm_make_request(KVM_REQ_PMU, vcpu); } + + kvm_reload_cet_supervisor_ssp(vcpu); + static_call(kvm_x86_sched_in)(vcpu, cpu); } +void kvm_arch_sched_out(struct kvm_vcpu *vcpu, int cpu) +{ + kvm_save_cet_supervisor_ssp(vcpu); +} + void kvm_arch_free_vm(struct kvm *kvm) { kfree(to_kvm_hv(kvm)->hv_pa_pg); diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h index d90331f16db1..b3032a5f0641 100644 --- a/include/linux/kvm_host.h +++ b/include/linux/kvm_host.h @@ -1423,6 +1423,7 @@ int kvm_arch_vcpu_ioctl_set_guest_debug(struct kvm_vcpu *vcpu, int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu); void kvm_arch_sched_in(struct kvm_vcpu *vcpu, int cpu); +void kvm_arch_sched_out(struct kvm_vcpu *vcpu, int cpu); void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu); void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu); diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index 66c1447d3c7f..42f28e8905e1 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -5885,6 +5885,7 @@ static void kvm_sched_out(struct preempt_notifier *pn, { struct kvm_vcpu *vcpu = preempt_notifier_to_vcpu(pn); + kvm_arch_sched_out(vcpu, 0); if (current->on_rq) { WRITE_ONCE(vcpu->preempted, true); WRITE_ONCE(vcpu->ready, true); -- 2.27.0