Re: [PATCH 07/11] KVM: arm64: Inject AArch64 exceptions from HYP

[James Morse <james.morse@arm.com>]

Hi Marc,

On 26/10/2020 13:34, Marc Zyngier wrote:
> Move the AArch64 exception injection code from EL1 to HYP, leaving
> only the ESR_EL1 updates to EL1. In order to come with the differences

(cope with the differences?)


> between VHE and nVHE, two set of system register accessors are provided.
> 
> SPSR, ELR, PC and PSTATE are now completely handled in the hypervisor.


> diff --git a/arch/arm64/kvm/hyp/exception.c b/arch/arm64/kvm/hyp/exception.c
> index 6533a9270850..cd6e643639e8 100644
> --- a/arch/arm64/kvm/hyp/exception.c
> +++ b/arch/arm64/kvm/hyp/exception.c
> @@ -11,7 +11,167 @@
>   */
>  
>  #include <hyp/adjust_pc.h>
> +#include <linux/kvm_host.h>
> +#include <asm/kvm_emulate.h>
> +
> +#if defined (__KVM_NVHE_HYPERVISOR__)
> +/*
> + * System registers are never loaded on the CPU until we actually
> + * restore them.
> + */
> +static inline u64 __vcpu_read_sys_reg(const struct kvm_vcpu *vcpu, int reg)
> +{
> +	return __vcpu_sys_reg(vcpu, reg);
> +}
> +
> +static inline void __vcpu_write_sys_reg(struct kvm_vcpu *vcpu, u64 val, int reg)
> +{
> +	 __vcpu_sys_reg(vcpu, reg) = val;
> +}
> +
> +static void __vcpu_write_spsr(struct kvm_vcpu *vcpu, u64 val)
> +{
> +	write_sysreg_el1(val, SYS_SPSR);
> +}
> +#elif defined (__KVM_VHE_HYPERVISOR__)
> +/* On VHE, all the registers are already loaded on the CPU */
> +static inline u64 __vcpu_read_sys_reg(const struct kvm_vcpu *vcpu, int reg)
> +{
> +	u64 val;

> +	if (__vcpu_read_sys_reg_from_cpu(reg, &val))
> +		return val;

As has_vhe()'s behaviour changes based on these KVM preprocessor symbols, would:
|	if (has_vhe() && __vcpu_read_sys_reg_from_cpu(reg, &val))
|		return val;

let you do both of these with only one copy of the function?


> +	return __vcpu_sys_reg(vcpu, reg);
> +}
> +
> +static inline void __vcpu_write_sys_reg(struct kvm_vcpu *vcpu, u64 val, int reg)
> +{
> +	if (__vcpu_write_sys_reg_to_cpu(val, reg))
> +		return;
> +
> +	 __vcpu_sys_reg(vcpu, reg) = val;
> +}


> +static void __vcpu_write_spsr(struct kvm_vcpu *vcpu, u64 val)
> +{
> +	write_sysreg_el1(val, SYS_SPSR);
> +}

This one doesn't look like it needs duplicating.


> +#else
> +#error Hypervisor code only!
> +#endif


Thanks,

James
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