From c139b6d1b4d27724987af5071177fb5f3d60c1e4 Mon Sep 17 00:00:00 2001 From: Marc Zyngier Date: Sun, 12 Jan 2025 16:50:28 +0000 Subject: [PATCH 1/2] KVM: arm64: nv: Always evaluate HCR_EL2 using sanitising accessors A lot of the NV code depends on HCR_EL2.{E2H,TGE}, and we assume in places that at least HCR_EL2.E2H is invariant for a given guest. However, we make a point in *not* using the sanitising accessor that would enforce this, and are at the mercy of the guest doing stupid things. Clearly, that's not good. Rework the HCR_EL2 accessors to use __vcpu_sys_reg() instead, guaranteeing that the RESx settings get applied, specially when HCR_EL2.E2H is evaluated. This results in fewer accessors overall. Huge thanks to Joey who spent a long time tracking this bug down. Reported-by: Joey Gouly Tested-by: Joey Gouly Reviewed-by: Joey Gouly Link: https://lore.kernel.org/r/20250112165029.1181056-2-maz@kernel.org Signed-off-by: Marc Zyngier --- arch/arm64/include/asm/kvm_emulate.h | 36 ++++++++++++---------------- arch/arm64/kvm/hyp/vhe/sysreg-sr.c | 4 ++-- 2 files changed, 17 insertions(+), 23 deletions(-) diff --git a/arch/arm64/include/asm/kvm_emulate.h b/arch/arm64/include/asm/kvm_emulate.h index cf811009a33c9..240b479b15c35 100644 --- a/arch/arm64/include/asm/kvm_emulate.h +++ b/arch/arm64/include/asm/kvm_emulate.h @@ -184,29 +184,30 @@ static inline bool vcpu_is_el2(const struct kvm_vcpu *vcpu) return vcpu_is_el2_ctxt(&vcpu->arch.ctxt); } -static inline bool __vcpu_el2_e2h_is_set(const struct kvm_cpu_context *ctxt) +static inline bool vcpu_el2_e2h_is_set(const struct kvm_vcpu *vcpu) { return (!cpus_have_final_cap(ARM64_HAS_HCR_NV1) || - (ctxt_sys_reg(ctxt, HCR_EL2) & HCR_E2H)); + (__vcpu_sys_reg(vcpu, HCR_EL2) & HCR_E2H)); } -static inline bool vcpu_el2_e2h_is_set(const struct kvm_vcpu *vcpu) +static inline bool vcpu_el2_tge_is_set(const struct kvm_vcpu *vcpu) { - return __vcpu_el2_e2h_is_set(&vcpu->arch.ctxt); + return ctxt_sys_reg(&vcpu->arch.ctxt, HCR_EL2) & HCR_TGE; } -static inline bool __vcpu_el2_tge_is_set(const struct kvm_cpu_context *ctxt) +static inline bool is_hyp_ctxt(const struct kvm_vcpu *vcpu) { - return ctxt_sys_reg(ctxt, HCR_EL2) & HCR_TGE; -} + bool e2h, tge; + u64 hcr; -static inline bool vcpu_el2_tge_is_set(const struct kvm_vcpu *vcpu) -{ - return __vcpu_el2_tge_is_set(&vcpu->arch.ctxt); -} + if (!vcpu_has_nv(vcpu)) + return false; + + hcr = __vcpu_sys_reg(vcpu, HCR_EL2); + + e2h = (hcr & HCR_E2H); + tge = (hcr & HCR_TGE); -static inline bool __is_hyp_ctxt(const struct kvm_cpu_context *ctxt) -{ /* * We are in a hypervisor context if the vcpu mode is EL2 or * E2H and TGE bits are set. The latter means we are in the user space @@ -215,14 +216,7 @@ static inline bool __is_hyp_ctxt(const struct kvm_cpu_context *ctxt) * Note that the HCR_EL2.{E2H,TGE}={0,1} isn't really handled in the * rest of the KVM code, and will result in a misbehaving guest. */ - return vcpu_is_el2_ctxt(ctxt) || - (__vcpu_el2_e2h_is_set(ctxt) && __vcpu_el2_tge_is_set(ctxt)) || - __vcpu_el2_tge_is_set(ctxt); -} - -static inline bool is_hyp_ctxt(const struct kvm_vcpu *vcpu) -{ - return vcpu_has_nv(vcpu) && __is_hyp_ctxt(&vcpu->arch.ctxt); + return vcpu_is_el2(vcpu) || (e2h && tge) || tge; } static inline bool vcpu_is_host_el0(const struct kvm_vcpu *vcpu) diff --git a/arch/arm64/kvm/hyp/vhe/sysreg-sr.c b/arch/arm64/kvm/hyp/vhe/sysreg-sr.c index 5f78a39053a79..90b018e06f2cb 100644 --- a/arch/arm64/kvm/hyp/vhe/sysreg-sr.c +++ b/arch/arm64/kvm/hyp/vhe/sysreg-sr.c @@ -216,7 +216,7 @@ void __vcpu_load_switch_sysregs(struct kvm_vcpu *vcpu) __sysreg32_restore_state(vcpu); __sysreg_restore_user_state(guest_ctxt); - if (unlikely(__is_hyp_ctxt(guest_ctxt))) { + if (unlikely(is_hyp_ctxt(vcpu))) { __sysreg_restore_vel2_state(vcpu); } else { if (vcpu_has_nv(vcpu)) { @@ -260,7 +260,7 @@ void __vcpu_put_switch_sysregs(struct kvm_vcpu *vcpu) host_ctxt = host_data_ptr(host_ctxt); - if (unlikely(__is_hyp_ctxt(guest_ctxt))) + if (unlikely(is_hyp_ctxt(vcpu))) __sysreg_save_vel2_state(vcpu); else __sysreg_save_el1_state(guest_ctxt); From 36f998de853cfad60508dfdfb41c9c40a2245f19 Mon Sep 17 00:00:00 2001 From: Marc Zyngier Date: Sun, 12 Jan 2025 16:50:29 +0000 Subject: [PATCH 2/2] KVM: arm64: nv: Apply RESx settings to sysreg reset values While we have sanitisation in place for the guest sysregs, we lack that sanitisation out of reset. So some of the fields could be evaluated and not reflect their RESx status, which sounds like a very bad idea. Apply the RESx masks to the the sysreg file in two situations: - when going via a reset of the sysregs - after having computed the RESx masks Having this separate reset phase from the actual reset handling is a bit grotty, but we need to apply this after the ID registers are final. Tested-by: Joey Gouly Reviewed-by: Joey Gouly Link: https://lore.kernel.org/r/20250112165029.1181056-3-maz@kernel.org Signed-off-by: Marc Zyngier --- arch/arm64/include/asm/kvm_nested.h | 2 +- arch/arm64/kvm/nested.c | 9 +++++++-- arch/arm64/kvm/sys_regs.c | 5 ++++- 3 files changed, 12 insertions(+), 4 deletions(-) diff --git a/arch/arm64/include/asm/kvm_nested.h b/arch/arm64/include/asm/kvm_nested.h index 233e655227164..f616e25e204f1 100644 --- a/arch/arm64/include/asm/kvm_nested.h +++ b/arch/arm64/include/asm/kvm_nested.h @@ -186,7 +186,7 @@ static inline bool kvm_supported_tlbi_s1e2_op(struct kvm_vcpu *vpcu, u32 instr) return true; } -int kvm_init_nv_sysregs(struct kvm *kvm); +int kvm_init_nv_sysregs(struct kvm_vcpu *vcpu); #ifdef CONFIG_ARM64_PTR_AUTH bool kvm_auth_eretax(struct kvm_vcpu *vcpu, u64 *elr); diff --git a/arch/arm64/kvm/nested.c b/arch/arm64/kvm/nested.c index 9b36218b48def..dd6480cf90ea5 100644 --- a/arch/arm64/kvm/nested.c +++ b/arch/arm64/kvm/nested.c @@ -963,14 +963,15 @@ static __always_inline void set_sysreg_masks(struct kvm *kvm, int sr, u64 res0, kvm->arch.sysreg_masks->mask[i].res1 = res1; } -int kvm_init_nv_sysregs(struct kvm *kvm) +int kvm_init_nv_sysregs(struct kvm_vcpu *vcpu) { + struct kvm *kvm = vcpu->kvm; u64 res0, res1; lockdep_assert_held(&kvm->arch.config_lock); if (kvm->arch.sysreg_masks) - return 0; + goto out; kvm->arch.sysreg_masks = kzalloc(sizeof(*(kvm->arch.sysreg_masks)), GFP_KERNEL_ACCOUNT); @@ -1271,6 +1272,10 @@ int kvm_init_nv_sysregs(struct kvm *kvm) res0 |= MDCR_EL2_EnSTEPOP; set_sysreg_masks(kvm, MDCR_EL2, res0, res1); +out: + for (enum vcpu_sysreg sr = __SANITISED_REG_START__; sr < NR_SYS_REGS; sr++) + (void)__vcpu_sys_reg(vcpu, sr); + return 0; } diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c index 83c6b4a07ef56..8671d46f53e59 100644 --- a/arch/arm64/kvm/sys_regs.c +++ b/arch/arm64/kvm/sys_regs.c @@ -4396,6 +4396,9 @@ void kvm_reset_sys_regs(struct kvm_vcpu *vcpu) reset_vcpu_ftr_id_reg(vcpu, r); else r->reset(vcpu, r); + + if (r->reg >= __SANITISED_REG_START__ && r->reg < NR_SYS_REGS) + (void)__vcpu_sys_reg(vcpu, r->reg); } set_bit(KVM_ARCH_FLAG_ID_REGS_INITIALIZED, &kvm->arch.flags); @@ -4999,7 +5002,7 @@ int kvm_finalize_sys_regs(struct kvm_vcpu *vcpu) } if (vcpu_has_nv(vcpu)) { - int ret = kvm_init_nv_sysregs(kvm); + int ret = kvm_init_nv_sysregs(vcpu); if (ret) return ret; }