On Thu, Oct 19, 2017 at 03:58:05PM +0100, James Morse wrote: > We expect to have firmware-first handling of RAS SErrors, with errors > notified via an APEI method. For systems without firmware-first, add > some minimal handling to KVM. > > There are two ways KVM can take an SError due to a guest, either may be a > RAS error: we exit the guest due to an SError routed to EL2 by HCR_EL2.AMO, > or we take an SError from EL2 when we unmask PSTATE.A from __guest_exit. > > The current SError from EL2 code unmasks SError and tries to fence any > pending SError into a single instruction window. It then leaves SError > unmasked. > > With the v8.2 RAS Extensions we may take an SError for a 'corrected' > error, but KVM is only able to handle SError from EL2 if they occur > during this single instruction window... > > The RAS Extensions give us a new instruction to synchronise and > consume SErrors. The RAS Extensions document (ARM DDI0587), > '2.4.1 ESB and Unrecoverable errors' describes ESB as synchronising > SError interrupts generated by 'instructions, translation table walks, > hardware updates to the translation tables, and instruction fetches on > the same PE'. This makes ESB equivalent to KVMs existing > 'dsb, mrs-daifclr, isb' sequence. > > Use the alternatives to synchronise and consume any SError using ESB > instead of unmasking and taking the SError. Set ARM_EXIT_WITH_SERROR_BIT > in the exit_code so that we can restart the vcpu if it turns out this > SError has no impact on the vcpu. > > Signed-off-by: James Morse <james.morse@xxxxxxx> Reviewed-by: Christoffer Dall <christoffer.dall@xxxxxxxxxx> > > --- > Changes since v3: > * Moved that nop out of the firing line > > arch/arm64/include/asm/kvm_emulate.h | 5 +++++ > arch/arm64/include/asm/kvm_host.h | 1 + > arch/arm64/kernel/asm-offsets.c | 1 + > arch/arm64/kvm/handle_exit.c | 10 +++++++++- > arch/arm64/kvm/hyp/entry.S | 13 +++++++++++++ > 5 files changed, 29 insertions(+), 1 deletion(-) > > diff --git a/arch/arm64/include/asm/kvm_emulate.h b/arch/arm64/include/asm/kvm_emulate.h > index 8a7a838eb17a..8274d16df3cd 100644 > --- a/arch/arm64/include/asm/kvm_emulate.h > +++ b/arch/arm64/include/asm/kvm_emulate.h > @@ -173,6 +173,11 @@ static inline phys_addr_t kvm_vcpu_get_fault_ipa(const struct kvm_vcpu *vcpu) > return ((phys_addr_t)vcpu->arch.fault.hpfar_el2 & HPFAR_MASK) << 8; > } > > +static inline u64 kvm_vcpu_get_disr(const struct kvm_vcpu *vcpu) > +{ > + return vcpu->arch.fault.disr_el1; > +} > + > static inline u32 kvm_vcpu_hvc_get_imm(const struct kvm_vcpu *vcpu) > { > return kvm_vcpu_get_hsr(vcpu) & ESR_ELx_xVC_IMM_MASK; > diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h > index 97438cc3a9ad..cf5d78ba14b5 100644 > --- a/arch/arm64/include/asm/kvm_host.h > +++ b/arch/arm64/include/asm/kvm_host.h > @@ -89,6 +89,7 @@ struct kvm_vcpu_fault_info { > u32 esr_el2; /* Hyp Syndrom Register */ > u64 far_el2; /* Hyp Fault Address Register */ > u64 hpfar_el2; /* Hyp IPA Fault Address Register */ > + u64 disr_el1; /* Deferred [SError] Status Register */ > }; > > /* > diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offsets.c > index 71bf088f1e4b..121889c49542 100644 > --- a/arch/arm64/kernel/asm-offsets.c > +++ b/arch/arm64/kernel/asm-offsets.c > @@ -130,6 +130,7 @@ int main(void) > BLANK(); > #ifdef CONFIG_KVM_ARM_HOST > DEFINE(VCPU_CONTEXT, offsetof(struct kvm_vcpu, arch.ctxt)); > + DEFINE(VCPU_FAULT_DISR, offsetof(struct kvm_vcpu, arch.fault.disr_el1)); > DEFINE(CPU_GP_REGS, offsetof(struct kvm_cpu_context, gp_regs)); > DEFINE(CPU_USER_PT_REGS, offsetof(struct kvm_regs, regs)); > DEFINE(CPU_FP_REGS, offsetof(struct kvm_regs, fp_regs)); > diff --git a/arch/arm64/kvm/handle_exit.c b/arch/arm64/kvm/handle_exit.c > index 345fdbba6c2e..e1e6cfe7d4d9 100644 > --- a/arch/arm64/kvm/handle_exit.c > +++ b/arch/arm64/kvm/handle_exit.c > @@ -23,6 +23,7 @@ > #include <linux/kvm_host.h> > > #include <asm/esr.h> > +#include <asm/exception.h> > #include <asm/kvm_asm.h> > #include <asm/kvm_coproc.h> > #include <asm/kvm_emulate.h> > @@ -208,7 +209,14 @@ int handle_exit(struct kvm_vcpu *vcpu, struct kvm_run *run, > *vcpu_pc(vcpu) -= adj; > } > > - kvm_inject_vabt(vcpu); > + if (cpus_have_const_cap(ARM64_HAS_RAS_EXTN)) { > + u64 disr = kvm_vcpu_get_disr(vcpu); > + > + kvm_handle_guest_serror(vcpu, disr_to_esr(disr)); > + } else { > + kvm_inject_vabt(vcpu); > + } > + > return 1; > } > > diff --git a/arch/arm64/kvm/hyp/entry.S b/arch/arm64/kvm/hyp/entry.S > index 12ee62d6d410..024c7afc78f8 100644 > --- a/arch/arm64/kvm/hyp/entry.S > +++ b/arch/arm64/kvm/hyp/entry.S > @@ -124,6 +124,17 @@ ENTRY(__guest_exit) > // Now restore the host regs > restore_callee_saved_regs x2 > > +alternative_if ARM64_HAS_RAS_EXTN > + // If we have the RAS extensions we can consume a pending error > + // without an unmask-SError and isb. > + esb > + mrs_s x2, SYS_DISR_EL1 > + str x2, [x1, #(VCPU_FAULT_DISR - VCPU_CONTEXT)] > + cbz x2, 1f > + msr_s SYS_DISR_EL1, xzr > + orr x0, x0, #(1<<ARM_EXIT_WITH_SERROR_BIT) > +1: ret > +alternative_else > // If we have a pending asynchronous abort, now is the > // time to find out. From your VAXorcist book, page 666: > // "Threaten me not, oh Evil one! For I speak with > @@ -134,7 +145,9 @@ ENTRY(__guest_exit) > mov x5, x0 > > dsb sy // Synchronize against in-flight ld/st > + nop > msr daifclr, #4 // Unmask aborts > +alternative_endif > > // This is our single instruction exception window. A pending > // SError is guaranteed to occur at the earliest when we unmask > -- > 2.13.3 > _______________________________________________ kvmarm mailing list kvmarm@xxxxxxxxxxxxxxxxxxxxx https://lists.cs.columbia.edu/mailman/listinfo/kvmarm