On Fri, Jul 17, 2020 at 02:52:33PM -0600, Rob Herring wrote:
> diff --git a/arch/arm64/include/asm/kvm_hyp.h b/arch/arm64/include/asm/kvm_hyp.h
> index ce3080834bfa..ce5b0d9b12bf 100644
> --- a/arch/arm64/include/asm/kvm_hyp.h
> +++ b/arch/arm64/include/asm/kvm_hyp.h
> @@ -46,6 +46,17 @@
> #define read_sysreg_el2(r) read_sysreg_elx(r, _EL2, _EL1)
> #define write_sysreg_el2(v,r) write_sysreg_elx(v, r, _EL2, _EL1)
>
> +static inline u64 __hyp_text read_sysreg_par(void)
> +{
> + u64 par;
> + if (cpus_have_const_cap(ARM64_WORKAROUND_1508412))
> + dmb(sy);
> + par = read_sysreg(par_el1);
> + if (cpus_have_const_cap(ARM64_WORKAROUND_1508412))
> + dmb(sy);
> + return par;
> +}
Even if that's not always called on a critical path, I agree with Andrew
that we could use alternatives here for dmb(sy).
> diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
> index baf5ce9225ce..3f798e0f1419 100644
> --- a/arch/arm64/kvm/sys_regs.c
> +++ b/arch/arm64/kvm/sys_regs.c
> @@ -94,10 +94,16 @@ static bool __vcpu_read_sys_reg_from_cpu(int reg, u64 *val)
> case TPIDR_EL1: *val = read_sysreg_s(SYS_TPIDR_EL1); break;
> case AMAIR_EL1: *val = read_sysreg_s(SYS_AMAIR_EL12); break;
> case CNTKCTL_EL1: *val = read_sysreg_s(SYS_CNTKCTL_EL12); break;
> - case PAR_EL1: *val = read_sysreg_s(SYS_PAR_EL1); break;
> case DACR32_EL2: *val = read_sysreg_s(SYS_DACR32_EL2); break;
> case IFSR32_EL2: *val = read_sysreg_s(SYS_IFSR32_EL2); break;
> case DBGVCR32_EL2: *val = read_sysreg_s(SYS_DBGVCR32_EL2); break;
> + case PAR_EL1:
> + if (cpus_have_const_cap(ARM64_WORKAROUND_1508412))
> + dmb(sy);
> + *val = read_sysreg_s(SYS_PAR_EL1);
> + if (cpus_have_const_cap(ARM64_WORKAROUND_1508412))
> + dmb(sy);
> + break;
> default: return false;
> }
Can't we use read_sysreg_par() directly here?
> diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c
> index 8afb238ff335..98609532e61a 100644
> --- a/arch/arm64/mm/fault.c
> +++ b/arch/arm64/mm/fault.c
> @@ -260,7 +260,17 @@ static bool __kprobes is_spurious_el1_translation_fault(unsigned long addr,
> local_irq_save(flags);
> asm volatile("at s1e1r, %0" :: "r" (addr));
> isb();
> + /*
> + * Arm Erratum 1508412 requires dmb(sy) before and after reads of
> + * PAR_EL1.
> + * As this location is not a hot path, just condition it on the config
> + * option.
> + */
> + if (IS_ENABLED(CONFIG_ARM64_ERRATUM_1508412))
> + dmb(sy);
> par = read_sysreg(par_el1);
> + if (IS_ENABLED(CONFIG_ARM64_ERRATUM_1508412))
> + dmb(sy);
> local_irq_restore(flags);
Why not read_sysreg_par()?
--
Catalin
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