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

[janani <janani@linux.ibm.com>]

On 2019-06-28 15:08, Claudio Carvalho wrote:
> 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.
> 
> Signed-off-by: Claudio Carvalho <cclaudio@linux.ibm.com>
> Reviewed-by: Ram Pai <linuxram@us.ibm.com>
> Reviewed-by: Ryan Grimm <grimm@linux.ibm.com>
> Acked-by: Madhavan Srinivasan <maddy@linux.vnet.ibm.com>
> Acked-by: Paul Mackerras <paulus@ozlabs.org>
  Reviewed-by: Janani Janakiraman <janani@linux.ibm.com>
> ---
>  arch/powerpc/kvm/book3s_hv_rmhandlers.S   | 2 ++
>  arch/powerpc/platforms/powernv/idle.c     | 6 ++++--
>  arch/powerpc/platforms/powernv/opal-imc.c | 4 ++++
>  3 files changed, 10 insertions(+), 2 deletions(-)
> 
> 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)
>  	isync
>  FTR_SECTION_ELSE
>  	/* On P9 we use the split_info for coordinating LPCR changes */
> diff --git a/arch/powerpc/platforms/powernv/idle.c
> b/arch/powerpc/platforms/powernv/idle.c
> index 77f2e0a4ee37..5593a2d55959 100644
> --- a/arch/powerpc/platforms/powernv/idle.c
> +++ b/arch/powerpc/platforms/powernv/idle.c
> @@ -679,7 +679,8 @@ static unsigned long power9_idle_stop(unsigned
> long psscr, bool mmu_on)
>  		sprs.ptcr	= mfspr(SPRN_PTCR);
>  		sprs.rpr	= mfspr(SPRN_RPR);
>  		sprs.tscr	= mfspr(SPRN_TSCR);
> -		sprs.ldbar	= mfspr(SPRN_LDBAR);
> +		if (!firmware_has_feature(FW_FEATURE_ULTRAVISOR))
> +			sprs.ldbar	= mfspr(SPRN_LDBAR);
> 
>  		sprs_saved = true;
> 
> @@ -762,7 +763,8 @@ static unsigned long power9_idle_stop(unsigned
> long psscr, bool mmu_on)
>  	mtspr(SPRN_PTCR,	sprs.ptcr);
>  	mtspr(SPRN_RPR,		sprs.rpr);
>  	mtspr(SPRN_TSCR,	sprs.tscr);
> -	mtspr(SPRN_LDBAR,	sprs.ldbar);
> +	if (!firmware_has_feature(FW_FEATURE_ULTRAVISOR))
> +		mtspr(SPRN_LDBAR,	sprs.ldbar);
> 
>  	if (pls >= pnv_first_tb_loss_level) {
>  		/* TB loss */
> 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;
> +
>  	/*
>  	 * Check whether this is kdump kernel. If yes, force the engines to
>  	 * stop and return.