Re: [PATCH v5 2/8] KVM: arm64: Make vcpu_{read,write}_sys_reg available to HYP code

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Low] The WARN_ON_ONCE checks in __vcpu_read_sysreg_vhe and __vcpu_write_sysreg_vhe contain impossible conditions.
--

--- Patch [2]: [PATCH v5 2/8] KVM: arm64: Make vcpu_{read,write}_sys_reg available to HYP code ---
commit fbd97ecacd267a88fbcb547ae114d7b3bbe56fb4
Author: Fuad Tabba <fuad.tabba@linux.dev>

KVM: arm64: Make vcpu_{read,write}_sys_reg available to HYP code

This patch renames the host-only implementations to
__vcpu_{read,write}_sysreg_vhe() and turns vcpu_{read,write}_sys_reg() into
context-dispatching wrappers. This allows helpers built on them to be shared
with hyp code.

> diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
> index 08ba882799d48..c6a416974a61f 100644
> --- a/arch/arm64/kvm/sys_regs.c
> +++ b/arch/arm64/kvm/sys_regs.c
> @@ -291,7 +291,7 @@ static void write_sr_to_cpu(enum vcpu_sysreg reg, u64 val)
>  	}
>  }
>  
> -u64 vcpu_read_sys_reg(const struct kvm_vcpu *vcpu, enum vcpu_sysreg reg)
> +u64 __vcpu_read_sysreg_vhe(const struct kvm_vcpu *vcpu, enum vcpu_sysreg reg)
>  {
>  	struct sr_loc loc = {};
>  

[Severity: Low]
Since the new vcpu_read_sys_reg() wrapper in kvm_emulate.h explicitly checks
has_vhe(), does this make the WARN_ON_ONCE(!has_vhe() ...) check inside this
function dead code?

Specifically, just below this declaration:

	locate_register(vcpu, reg, &loc);
	WARN_ON_ONCE(!has_vhe() && loc.loc != SR_LOC_MEMORY);

Is it worth removing the check now that the caller guarantees has_vhe()
is true?

[ ... ]

> @@ -338,7 +338,7 @@ u64 vcpu_read_sys_reg(const struct kvm_vcpu *vcpu, enum vcpu_sysreg reg)
>  	return __vcpu_sys_reg(vcpu, reg);
>  }
>  
> -void vcpu_write_sys_reg(struct kvm_vcpu *vcpu, u64 val, enum vcpu_sysreg reg)
> +void __vcpu_write_sysreg_vhe(struct kvm_vcpu *vcpu, u64 val, enum vcpu_sysreg reg)
>  {
>  	struct sr_loc loc = {};
>  

[Severity: Low]
Similarly, does the WARN_ON_ONCE(!has_vhe() ...) check inside this function
become unreachable now that the wrapper only calls this when has_vhe()
is true?

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260714101601.4142645-1-fuad.tabba@linux.dev?part=2