From b5b9955617bc0b41546f2fa7c3dbcc048b43dc82 Mon Sep 17 00:00:00 2001 From: Fuad Tabba Date: Mon, 3 Jun 2024 13:28:48 +0100 Subject: KVM: arm64: Eagerly restore host fpsimd/sve state in pKVM When running in protected mode we don't want to leak protected guest state to the host, including whether a guest has used fpsimd/sve. Therefore, eagerly restore the host state on guest exit when running in protected mode, which happens only if the guest has used fpsimd/sve. Reviewed-by: Oliver Upton Signed-off-by: Fuad Tabba Link: https://lore.kernel.org/r/20240603122852.3923848-7-tabba@google.com Signed-off-by: Marc Zyngier --- arch/arm64/kvm/hyp/include/hyp/switch.h | 13 ++++++- arch/arm64/kvm/hyp/nvhe/hyp-main.c | 67 +++++++++++++++++++++++++++++++-- arch/arm64/kvm/hyp/nvhe/pkvm.c | 2 + arch/arm64/kvm/hyp/nvhe/switch.c | 16 +++++++- 4 files changed, 93 insertions(+), 5 deletions(-) diff --git a/arch/arm64/kvm/hyp/include/hyp/switch.h b/arch/arm64/kvm/hyp/include/hyp/switch.h index 9b904c858df0..0c4de44534b7 100644 --- a/arch/arm64/kvm/hyp/include/hyp/switch.h +++ b/arch/arm64/kvm/hyp/include/hyp/switch.h @@ -321,6 +321,17 @@ static inline void __hyp_sve_restore_guest(struct kvm_vcpu *vcpu) write_sysreg_el1(__vcpu_sys_reg(vcpu, ZCR_EL1), SYS_ZCR); } +static inline void __hyp_sve_save_host(void) +{ + struct cpu_sve_state *sve_state = *host_data_ptr(sve_state); + + sve_state->zcr_el1 = read_sysreg_el1(SYS_ZCR); + write_sysreg_s(ZCR_ELx_LEN_MASK, SYS_ZCR_EL2); + __sve_save_state(sve_state->sve_regs + sve_ffr_offset(kvm_host_sve_max_vl), + &sve_state->fpsr, + true); +} + static void kvm_hyp_save_fpsimd_host(struct kvm_vcpu *vcpu); /* @@ -355,7 +366,7 @@ static bool kvm_hyp_handle_fpsimd(struct kvm_vcpu *vcpu, u64 *exit_code) /* Valid trap. Switch the context: */ /* First disable enough traps to allow us to update the registers */ - if (sve_guest) + if (sve_guest || (is_protected_kvm_enabled() && system_supports_sve())) cpacr_clear_set(0, CPACR_ELx_FPEN | CPACR_ELx_ZEN); else cpacr_clear_set(0, CPACR_ELx_FPEN); diff --git a/arch/arm64/kvm/hyp/nvhe/hyp-main.c b/arch/arm64/kvm/hyp/nvhe/hyp-main.c index f71394d0e32a..bd93b8a9e172 100644 --- a/arch/arm64/kvm/hyp/nvhe/hyp-main.c +++ b/arch/arm64/kvm/hyp/nvhe/hyp-main.c @@ -23,20 +23,80 @@ DEFINE_PER_CPU(struct kvm_nvhe_init_params, kvm_init_params); void __kvm_hyp_host_forward_smc(struct kvm_cpu_context *host_ctxt); +static void __hyp_sve_save_guest(struct kvm_vcpu *vcpu) +{ + __vcpu_sys_reg(vcpu, ZCR_EL1) = read_sysreg_el1(SYS_ZCR); + /* + * On saving/restoring guest sve state, always use the maximum VL for + * the guest. The layout of the data when saving the sve state depends + * on the VL, so use a consistent (i.e., the maximum) guest VL. + */ + sve_cond_update_zcr_vq(vcpu_sve_max_vq(vcpu) - 1, SYS_ZCR_EL2); + __sve_save_state(vcpu_sve_pffr(vcpu), &vcpu->arch.ctxt.fp_regs.fpsr, true); + write_sysreg_s(ZCR_ELx_LEN_MASK, SYS_ZCR_EL2); +} + +static void __hyp_sve_restore_host(void) +{ + struct cpu_sve_state *sve_state = *host_data_ptr(sve_state); + + /* + * On saving/restoring host sve state, always use the maximum VL for + * the host. The layout of the data when saving the sve state depends + * on the VL, so use a consistent (i.e., the maximum) host VL. + * + * Setting ZCR_EL2 to ZCR_ELx_LEN_MASK sets the effective length + * supported by the system (or limited at EL3). + */ + write_sysreg_s(ZCR_ELx_LEN_MASK, SYS_ZCR_EL2); + __sve_restore_state(sve_state->sve_regs + sve_ffr_offset(kvm_host_sve_max_vl), + &sve_state->fpsr, + true); + write_sysreg_el1(sve_state->zcr_el1, SYS_ZCR); +} + +static void fpsimd_sve_flush(void) +{ + *host_data_ptr(fp_owner) = FP_STATE_HOST_OWNED; +} + +static void fpsimd_sve_sync(struct kvm_vcpu *vcpu) +{ + if (!guest_owns_fp_regs()) + return; + + cpacr_clear_set(0, CPACR_ELx_FPEN | CPACR_ELx_ZEN); + isb(); + + if (vcpu_has_sve(vcpu)) + __hyp_sve_save_guest(vcpu); + else + __fpsimd_save_state(&vcpu->arch.ctxt.fp_regs); + + if (system_supports_sve()) + __hyp_sve_restore_host(); + else + __fpsimd_restore_state(*host_data_ptr(fpsimd_state)); + + *host_data_ptr(fp_owner) = FP_STATE_HOST_OWNED; +} + static void flush_hyp_vcpu(struct pkvm_hyp_vcpu *hyp_vcpu) { struct kvm_vcpu *host_vcpu = hyp_vcpu->host_vcpu; + fpsimd_sve_flush(); + hyp_vcpu->vcpu.arch.ctxt = host_vcpu->arch.ctxt; hyp_vcpu->vcpu.arch.sve_state = kern_hyp_va(host_vcpu->arch.sve_state); - hyp_vcpu->vcpu.arch.sve_max_vl = host_vcpu->arch.sve_max_vl; + /* Limit guest vector length to the maximum supported by the host. */ + hyp_vcpu->vcpu.arch.sve_max_vl = min(host_vcpu->arch.sve_max_vl, kvm_host_sve_max_vl); hyp_vcpu->vcpu.arch.hw_mmu = host_vcpu->arch.hw_mmu; hyp_vcpu->vcpu.arch.hcr_el2 = host_vcpu->arch.hcr_el2; hyp_vcpu->vcpu.arch.mdcr_el2 = host_vcpu->arch.mdcr_el2; - hyp_vcpu->vcpu.arch.cptr_el2 = host_vcpu->arch.cptr_el2; hyp_vcpu->vcpu.arch.iflags = host_vcpu->arch.iflags; @@ -54,10 +114,11 @@ static void sync_hyp_vcpu(struct pkvm_hyp_vcpu *hyp_vcpu) struct vgic_v3_cpu_if *host_cpu_if = &host_vcpu->arch.vgic_cpu.vgic_v3; unsigned int i; + fpsimd_sve_sync(&hyp_vcpu->vcpu); + host_vcpu->arch.ctxt = hyp_vcpu->vcpu.arch.ctxt; host_vcpu->arch.hcr_el2 = hyp_vcpu->vcpu.arch.hcr_el2; - host_vcpu->arch.cptr_el2 = hyp_vcpu->vcpu.arch.cptr_el2; host_vcpu->arch.fault = hyp_vcpu->vcpu.arch.fault; diff --git a/arch/arm64/kvm/hyp/nvhe/pkvm.c b/arch/arm64/kvm/hyp/nvhe/pkvm.c index 25e9a94f6d76..feb27b4ce459 100644 --- a/arch/arm64/kvm/hyp/nvhe/pkvm.c +++ b/arch/arm64/kvm/hyp/nvhe/pkvm.c @@ -588,6 +588,8 @@ unlock: if (ret) unmap_donated_memory(hyp_vcpu, sizeof(*hyp_vcpu)); + hyp_vcpu->vcpu.arch.cptr_el2 = kvm_get_reset_cptr_el2(&hyp_vcpu->vcpu); + return ret; } diff --git a/arch/arm64/kvm/hyp/nvhe/switch.c b/arch/arm64/kvm/hyp/nvhe/switch.c index 019f863922fa..bef74de7065b 100644 --- a/arch/arm64/kvm/hyp/nvhe/switch.c +++ b/arch/arm64/kvm/hyp/nvhe/switch.c @@ -184,7 +184,21 @@ static bool kvm_handle_pvm_sys64(struct kvm_vcpu *vcpu, u64 *exit_code) static void kvm_hyp_save_fpsimd_host(struct kvm_vcpu *vcpu) { - __fpsimd_save_state(*host_data_ptr(fpsimd_state)); + /* + * Non-protected kvm relies on the host restoring its sve state. + * Protected kvm restores the host's sve state as not to reveal that + * fpsimd was used by a guest nor leak upper sve bits. + */ + if (unlikely(is_protected_kvm_enabled() && system_supports_sve())) { + __hyp_sve_save_host(); + + /* Re-enable SVE traps if not supported for the guest vcpu. */ + if (!vcpu_has_sve(vcpu)) + cpacr_clear_set(CPACR_ELx_ZEN, 0); + + } else { + __fpsimd_save_state(*host_data_ptr(fpsimd_state)); + } } static const exit_handler_fn hyp_exit_handlers[] = { -- cgit v1.2.3