[PATCH v4 6/8] KVM: PPC: Ultravisor: Restrict LDBAR access

[Michael Ellerman]

Claudio Carvalho <cclaudio at linux.ibm.com> writes:
> When the ultravisor firmware is available, it takes control over the
> LDBAR register. In this case, thread-imc updates and save/restore
> operations on the LDBAR register are handled by ultravisor.

Please roll up the replies to Alexey's question about LDBAR into the
change log.

> diff --git a/arch/powerpc/kvm/book3s_hv_rmhandlers.S b/arch/powerpc/kvm/book3s_hv_rmhandlers.S
> index f9b2620fbecd..cffb365d9d02 100644
> --- a/arch/powerpc/kvm/book3s_hv_rmhandlers.S
> +++ b/arch/powerpc/kvm/book3s_hv_rmhandlers.S
> @@ -375,8 +375,10 @@ BEGIN_FTR_SECTION
>  	mtspr	SPRN_RPR, r0
>  	ld	r0, KVM_SPLIT_PMMAR(r6)
>  	mtspr	SPRN_PMMAR, r0
> +BEGIN_FW_FTR_SECTION_NESTED(70)
>  	ld	r0, KVM_SPLIT_LDBAR(r6)
>  	mtspr	SPRN_LDBAR, r0
> +END_FW_FTR_SECTION_NESTED(FW_FEATURE_ULTRAVISOR, 0, 70)

That's in Power8 code isn't it? Which will never have an ultravisor.

> diff --git a/arch/powerpc/platforms/powernv/opal-imc.c b/arch/powerpc/platforms/powernv/opal-imc.c
> index 1b6932890a73..5fe2d4526cbc 100644
> --- a/arch/powerpc/platforms/powernv/opal-imc.c
> +++ b/arch/powerpc/platforms/powernv/opal-imc.c
> @@ -254,6 +254,10 @@ static int opal_imc_counters_probe(struct platform_device *pdev)
>  	bool core_imc_reg = false, thread_imc_reg = false;
>  	u32 type;
>  
> +	/* Disable IMC devices, when Ultravisor is enabled. */
> +	if (firmware_has_feature(FW_FEATURE_ULTRAVISOR))
> +		return -EACCES;

I don't mind taking this change. But at the same time should the IMC
stuff just be omitted from the device tree when we're in ultravisor mode?

cheers