From 77ee70a073575977b403e9add25f185d614217d8 Mon Sep 17 00:00:00 2001 From: Oliver Upton Date: Tue, 8 Jul 2025 10:25:11 -0700 Subject: [PATCH] KVM: arm64: nv: Honor SError exception routing / masking To date KVM has used HCR_EL2.VSE to track the state of a pending SError for the guest. With this bit set, hardware respects the EL1 exception routing / masking rules and injects the vSError when appropriate. This isn't correct for NV guests as hardware is oblivious to vEL2's intentions for SErrors. Better yet, with FEAT_NV2 the guest can change the routing behind our back as HCR_EL2 is redirected to memory. Cope with this mess by: - Using a flag (instead of HCR_EL2.VSE) to track the pending SError state when SErrors are unconditionally masked for the current context - Resampling the routing / masking of a pending SError on every guest entry/exit - Emulating exception entry when SError routing implies a translation regime change Reviewed-by: Marc Zyngier Link: https://lore.kernel.org/r/20250708172532.1699409-7-oliver.upton@linux.dev Signed-off-by: Oliver Upton --- arch/arm64/include/asm/kvm_emulate.h | 20 +++++++++++++- arch/arm64/include/asm/kvm_host.h | 18 ++++++++++--- arch/arm64/include/asm/kvm_nested.h | 2 ++ arch/arm64/kvm/arm.c | 4 +++ arch/arm64/kvm/emulate-nested.c | 14 ++++++++++ arch/arm64/kvm/guest.c | 33 ++++++++++++++--------- arch/arm64/kvm/handle_exit.c | 4 +-- arch/arm64/kvm/hyp/exception.c | 6 ++++- arch/arm64/kvm/inject_fault.c | 39 +++++++++++++++------------ arch/arm64/kvm/mmu.c | 2 +- arch/arm64/kvm/nested.c | 40 ++++++++++++++++++++++++++++ 11 files changed, 144 insertions(+), 38 deletions(-) diff --git a/arch/arm64/include/asm/kvm_emulate.h b/arch/arm64/include/asm/kvm_emulate.h index 3a27ed4de9ac1..daa0410aaebf2 100644 --- a/arch/arm64/include/asm/kvm_emulate.h +++ b/arch/arm64/include/asm/kvm_emulate.h @@ -45,7 +45,7 @@ bool kvm_condition_valid32(const struct kvm_vcpu *vcpu); void kvm_skip_instr32(struct kvm_vcpu *vcpu); void kvm_inject_undefined(struct kvm_vcpu *vcpu); -void kvm_inject_vabt(struct kvm_vcpu *vcpu); +int kvm_inject_serror_esr(struct kvm_vcpu *vcpu, u64 esr); int kvm_inject_sea(struct kvm_vcpu *vcpu, bool iabt, u64 addr); void kvm_inject_size_fault(struct kvm_vcpu *vcpu); @@ -59,12 +59,25 @@ static inline int kvm_inject_sea_iabt(struct kvm_vcpu *vcpu, u64 addr) return kvm_inject_sea(vcpu, true, addr); } +static inline int kvm_inject_serror(struct kvm_vcpu *vcpu) +{ + /* + * ESR_ELx.ISV (later renamed to IDS) indicates whether or not + * ESR_ELx.ISS contains IMPLEMENTATION DEFINED syndrome information. + * + * Set the bit when injecting an SError w/o an ESR to indicate ISS + * does not follow the architected format. + */ + return kvm_inject_serror_esr(vcpu, ESR_ELx_ISV); +} + void kvm_vcpu_wfi(struct kvm_vcpu *vcpu); void kvm_emulate_nested_eret(struct kvm_vcpu *vcpu); int kvm_inject_nested_sync(struct kvm_vcpu *vcpu, u64 esr_el2); int kvm_inject_nested_irq(struct kvm_vcpu *vcpu); int kvm_inject_nested_sea(struct kvm_vcpu *vcpu, bool iabt, u64 addr); +int kvm_inject_nested_serror(struct kvm_vcpu *vcpu, u64 esr); static inline void kvm_inject_nested_sve_trap(struct kvm_vcpu *vcpu) { @@ -205,6 +218,11 @@ static inline bool vcpu_el2_tge_is_set(const struct kvm_vcpu *vcpu) return ctxt_sys_reg(&vcpu->arch.ctxt, HCR_EL2) & HCR_TGE; } +static inline bool vcpu_el2_amo_is_set(const struct kvm_vcpu *vcpu) +{ + return ctxt_sys_reg(&vcpu->arch.ctxt, HCR_EL2) & HCR_AMO; +} + static inline bool is_hyp_ctxt(const struct kvm_vcpu *vcpu) { bool e2h, tge; diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h index d27079968341c..8af4a5d400779 100644 --- a/arch/arm64/include/asm/kvm_host.h +++ b/arch/arm64/include/asm/kvm_host.h @@ -817,7 +817,7 @@ struct kvm_vcpu_arch { u8 iflags; /* State flags for kernel bookkeeping, unused by the hypervisor code */ - u8 sflags; + u16 sflags; /* * Don't run the guest (internal implementation need). @@ -953,9 +953,21 @@ struct kvm_vcpu_arch { __vcpu_flags_preempt_enable(); \ } while (0) +#define __vcpu_test_and_clear_flag(v, flagset, f, m) \ + ({ \ + typeof(v->arch.flagset) set; \ + \ + set = __vcpu_get_flag(v, flagset, f, m); \ + __vcpu_clear_flag(v, flagset, f, m); \ + \ + set; \ + }) + #define vcpu_get_flag(v, ...) __vcpu_get_flag((v), __VA_ARGS__) #define vcpu_set_flag(v, ...) __vcpu_set_flag((v), __VA_ARGS__) #define vcpu_clear_flag(v, ...) __vcpu_clear_flag((v), __VA_ARGS__) +#define vcpu_test_and_clear_flag(v, ...) \ + __vcpu_test_and_clear_flag((v), __VA_ARGS__) /* KVM_ARM_VCPU_INIT completed */ #define VCPU_INITIALIZED __vcpu_single_flag(cflags, BIT(0)) @@ -1015,6 +1027,8 @@ struct kvm_vcpu_arch { #define IN_WFI __vcpu_single_flag(sflags, BIT(6)) /* KVM is currently emulating a nested ERET */ #define IN_NESTED_ERET __vcpu_single_flag(sflags, BIT(7)) +/* SError pending for nested guest */ +#define NESTED_SERROR_PENDING __vcpu_single_flag(sflags, BIT(8)) /* Pointer to the vcpu's SVE FFR for sve_{save,load}_state() */ @@ -1387,8 +1401,6 @@ static inline bool kvm_arm_is_pvtime_enabled(struct kvm_vcpu_arch *vcpu_arch) return (vcpu_arch->steal.base != INVALID_GPA); } -void kvm_set_sei_esr(struct kvm_vcpu *vcpu, u64 syndrome); - struct kvm_vcpu *kvm_mpidr_to_vcpu(struct kvm *kvm, unsigned long mpidr); DECLARE_KVM_HYP_PER_CPU(struct kvm_host_data, kvm_host_data); diff --git a/arch/arm64/include/asm/kvm_nested.h b/arch/arm64/include/asm/kvm_nested.h index 0bd07ea068a1f..7fd76f41c296a 100644 --- a/arch/arm64/include/asm/kvm_nested.h +++ b/arch/arm64/include/asm/kvm_nested.h @@ -80,6 +80,8 @@ extern void kvm_vcpu_load_hw_mmu(struct kvm_vcpu *vcpu); extern void kvm_vcpu_put_hw_mmu(struct kvm_vcpu *vcpu); extern void check_nested_vcpu_requests(struct kvm_vcpu *vcpu); +extern void kvm_nested_flush_hwstate(struct kvm_vcpu *vcpu); +extern void kvm_nested_sync_hwstate(struct kvm_vcpu *vcpu); struct kvm_s2_trans { phys_addr_t output; diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c index bbe7b98e1ce3b..c664f3a7883aa 100644 --- a/arch/arm64/kvm/arm.c +++ b/arch/arm64/kvm/arm.c @@ -1188,6 +1188,8 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu) */ preempt_disable(); + kvm_nested_flush_hwstate(vcpu); + if (kvm_vcpu_has_pmu(vcpu)) kvm_pmu_flush_hwstate(vcpu); @@ -1287,6 +1289,8 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu) /* Exit types that need handling before we can be preempted */ handle_exit_early(vcpu, ret); + kvm_nested_sync_hwstate(vcpu); + preempt_enable(); /* diff --git a/arch/arm64/kvm/emulate-nested.c b/arch/arm64/kvm/emulate-nested.c index 65a2471c5638f..b01a482b41bed 100644 --- a/arch/arm64/kvm/emulate-nested.c +++ b/arch/arm64/kvm/emulate-nested.c @@ -2714,6 +2714,9 @@ static void kvm_inject_el2_exception(struct kvm_vcpu *vcpu, u64 esr_el2, case except_type_irq: kvm_pend_exception(vcpu, EXCEPT_AA64_EL2_IRQ); break; + case except_type_serror: + kvm_pend_exception(vcpu, EXCEPT_AA64_EL2_SERR); + break; default: WARN_ONCE(1, "Unsupported EL2 exception injection %d\n", type); } @@ -2821,3 +2824,14 @@ int kvm_inject_nested_sea(struct kvm_vcpu *vcpu, bool iabt, u64 addr) vcpu_write_sys_reg(vcpu, FAR_EL2, addr); return kvm_inject_nested_sync(vcpu, esr); } + +int kvm_inject_nested_serror(struct kvm_vcpu *vcpu, u64 esr) +{ + /* + * Hardware sets up the EC field when propagating ESR as a result of + * vSError injection. Manually populate EC for an emulated SError + * exception. + */ + esr |= FIELD_PREP(ESR_ELx_EC_MASK, ESR_ELx_EC_SERROR); + return kvm_inject_nested(vcpu, esr, except_type_serror); +} diff --git a/arch/arm64/kvm/guest.c b/arch/arm64/kvm/guest.c index 8983a43fb45e9..e2702718d56d2 100644 --- a/arch/arm64/kvm/guest.c +++ b/arch/arm64/kvm/guest.c @@ -818,8 +818,9 @@ int kvm_arch_vcpu_ioctl_set_sregs(struct kvm_vcpu *vcpu, int __kvm_arm_vcpu_get_events(struct kvm_vcpu *vcpu, struct kvm_vcpu_events *events) { - events->exception.serror_pending = !!(vcpu->arch.hcr_el2 & HCR_VSE); events->exception.serror_has_esr = cpus_have_final_cap(ARM64_HAS_RAS_EXTN); + events->exception.serror_pending = (vcpu->arch.hcr_el2 & HCR_VSE) || + vcpu_get_flag(vcpu, NESTED_SERROR_PENDING); if (events->exception.serror_pending && events->exception.serror_has_esr) events->exception.serror_esr = vcpu_get_vsesr(vcpu); @@ -839,23 +840,29 @@ int __kvm_arm_vcpu_set_events(struct kvm_vcpu *vcpu, bool serror_pending = events->exception.serror_pending; bool has_esr = events->exception.serror_has_esr; bool ext_dabt_pending = events->exception.ext_dabt_pending; + u64 esr = events->exception.serror_esr; int ret = 0; - if (serror_pending && has_esr) { - if (!cpus_have_final_cap(ARM64_HAS_RAS_EXTN)) - return -EINVAL; - - if (!((events->exception.serror_esr) & ~ESR_ELx_ISS_MASK)) - kvm_set_sei_esr(vcpu, events->exception.serror_esr); - else - return -EINVAL; - } else if (serror_pending) { - kvm_inject_vabt(vcpu); - } - if (ext_dabt_pending) ret = kvm_inject_sea_dabt(vcpu, kvm_vcpu_get_hfar(vcpu)); + if (ret < 0) + return ret; + + if (!serror_pending) + return 0; + + if (!cpus_have_final_cap(ARM64_HAS_RAS_EXTN) && has_esr) + return -EINVAL; + + if (has_esr && (esr & ~ESR_ELx_ISS_MASK)) + return -EINVAL; + + if (has_esr) + ret = kvm_inject_serror_esr(vcpu, esr); + else + ret = kvm_inject_serror(vcpu); + return (ret < 0) ? ret : 0; } diff --git a/arch/arm64/kvm/handle_exit.c b/arch/arm64/kvm/handle_exit.c index c37c58d9d25d6..a598072f36d2c 100644 --- a/arch/arm64/kvm/handle_exit.c +++ b/arch/arm64/kvm/handle_exit.c @@ -32,7 +32,7 @@ typedef int (*exit_handle_fn)(struct kvm_vcpu *); static void kvm_handle_guest_serror(struct kvm_vcpu *vcpu, u64 esr) { if (!arm64_is_ras_serror(esr) || arm64_is_fatal_ras_serror(NULL, esr)) - kvm_inject_vabt(vcpu); + kvm_inject_serror(vcpu); } static int handle_hvc(struct kvm_vcpu *vcpu) @@ -490,7 +490,7 @@ void handle_exit_early(struct kvm_vcpu *vcpu, int exception_index) kvm_handle_guest_serror(vcpu, disr_to_esr(disr)); } else { - kvm_inject_vabt(vcpu); + kvm_inject_serror(vcpu); } return; diff --git a/arch/arm64/kvm/hyp/exception.c b/arch/arm64/kvm/hyp/exception.c index 6a2a899a344e6..592adc78b1496 100644 --- a/arch/arm64/kvm/hyp/exception.c +++ b/arch/arm64/kvm/hyp/exception.c @@ -347,9 +347,13 @@ static void kvm_inject_exception(struct kvm_vcpu *vcpu) enter_exception64(vcpu, PSR_MODE_EL2h, except_type_irq); break; + case unpack_vcpu_flag(EXCEPT_AA64_EL2_SERR): + enter_exception64(vcpu, PSR_MODE_EL2h, except_type_serror); + break; + default: /* - * Only EL1_SYNC and EL2_{SYNC,IRQ} makes + * Only EL1_SYNC and EL2_{SYNC,IRQ,SERR} makes * sense so far. Everything else gets silently * ignored. */ diff --git a/arch/arm64/kvm/inject_fault.c b/arch/arm64/kvm/inject_fault.c index d9fa4046b6021..10773a8ef4cbb 100644 --- a/arch/arm64/kvm/inject_fault.c +++ b/arch/arm64/kvm/inject_fault.c @@ -219,25 +219,30 @@ void kvm_inject_undefined(struct kvm_vcpu *vcpu) inject_undef64(vcpu); } -void kvm_set_sei_esr(struct kvm_vcpu *vcpu, u64 esr) +static bool kvm_serror_target_is_el2(struct kvm_vcpu *vcpu) { - vcpu_set_vsesr(vcpu, esr & ESR_ELx_ISS_MASK); - *vcpu_hcr(vcpu) |= HCR_VSE; + return is_hyp_ctxt(vcpu) || vcpu_el2_amo_is_set(vcpu); } -/** - * kvm_inject_vabt - inject an async abort / SError into the guest - * @vcpu: The VCPU to receive the exception - * - * It is assumed that this code is called from the VCPU thread and that the - * VCPU therefore is not currently executing guest code. - * - * Systems with the RAS Extensions specify an imp-def ESR (ISV/IDS = 1) with - * the remaining ISS all-zeros so that this error is not interpreted as an - * uncategorized RAS error. Without the RAS Extensions we can't specify an ESR - * value, so the CPU generates an imp-def value. - */ -void kvm_inject_vabt(struct kvm_vcpu *vcpu) +static bool kvm_serror_undeliverable_at_el2(struct kvm_vcpu *vcpu) { - kvm_set_sei_esr(vcpu, ESR_ELx_ISV); + return !(vcpu_el2_tge_is_set(vcpu) || vcpu_el2_amo_is_set(vcpu)); +} + +int kvm_inject_serror_esr(struct kvm_vcpu *vcpu, u64 esr) +{ + lockdep_assert_held(&vcpu->mutex); + + if (is_nested_ctxt(vcpu) && kvm_serror_target_is_el2(vcpu)) + return kvm_inject_nested_serror(vcpu, esr); + + if (vcpu_is_el2(vcpu) && kvm_serror_undeliverable_at_el2(vcpu)) { + vcpu_set_vsesr(vcpu, esr); + vcpu_set_flag(vcpu, NESTED_SERROR_PENDING); + return 1; + } + + vcpu_set_vsesr(vcpu, esr & ESR_ELx_ISS_MASK); + *vcpu_hcr(vcpu) |= HCR_VSE; + return 1; } diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c index f05d70dd6d51d..2c3094181f9cd 100644 --- a/arch/arm64/kvm/mmu.c +++ b/arch/arm64/kvm/mmu.c @@ -1808,7 +1808,7 @@ int kvm_handle_guest_abort(struct kvm_vcpu *vcpu) * There is no need to pass the error into the guest. */ if (kvm_handle_guest_sea()) - kvm_inject_vabt(vcpu); + return kvm_inject_serror(vcpu); return 1; } diff --git a/arch/arm64/kvm/nested.c b/arch/arm64/kvm/nested.c index 5b191f4dc5668..4218172ed1a4c 100644 --- a/arch/arm64/kvm/nested.c +++ b/arch/arm64/kvm/nested.c @@ -1782,3 +1782,43 @@ void check_nested_vcpu_requests(struct kvm_vcpu *vcpu) if (kvm_check_request(KVM_REQ_GUEST_HYP_IRQ_PENDING, vcpu)) kvm_inject_nested_irq(vcpu); } + +/* + * One of the many architectural bugs in FEAT_NV2 is that the guest hypervisor + * can write to HCR_EL2 behind our back, potentially changing the exception + * routing / masking for even the host context. + * + * What follows is some slop to (1) react to exception routing / masking and (2) + * preserve the pending SError state across translation regimes. + */ +void kvm_nested_flush_hwstate(struct kvm_vcpu *vcpu) +{ + if (!vcpu_has_nv(vcpu)) + return; + + if (unlikely(vcpu_test_and_clear_flag(vcpu, NESTED_SERROR_PENDING))) + kvm_inject_serror_esr(vcpu, vcpu_get_vsesr(vcpu)); +} + +void kvm_nested_sync_hwstate(struct kvm_vcpu *vcpu) +{ + unsigned long *hcr = vcpu_hcr(vcpu); + + if (!vcpu_has_nv(vcpu)) + return; + + /* + * We previously decided that an SError was deliverable to the guest. + * Reap the pending state from HCR_EL2 and... + */ + if (unlikely(__test_and_clear_bit(__ffs(HCR_VSE), hcr))) + vcpu_set_flag(vcpu, NESTED_SERROR_PENDING); + + /* + * Re-attempt SError injection in case the deliverability has changed, + * which is necessary to faithfully emulate WFI the case of a pending + * SError being a wakeup condition. + */ + if (unlikely(vcpu_test_and_clear_flag(vcpu, NESTED_SERROR_PENDING))) + kvm_inject_serror_esr(vcpu, vcpu_get_vsesr(vcpu)); +} -- 2.47.2