Re: [PATCH v3 7/9] KVM: PPC: Ultravisor: Restrict LDBAR access

From: Madhavan Srinivasan <maddy@linux.vnet.ibm.com>
To: Claudio Carvalho <cclaudio@linux.ibm.com>, linuxppc-dev@ozlabs.org
Cc: Thiago Bauermann <bauermann@linux.ibm.com>,
	Michael Anderson <andmike@linux.ibm.com>,
	Ram Pai <linuxram@us.ibm.com>,
	kvm-ppc@vger.kernel.org, Bharata B Rao <bharata@linux.ibm.com>,
	Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>,
	Anshuman Khandual <khandual@linux.vnet.ibm.com>
Subject: Re: [PATCH v3 7/9] KVM: PPC: Ultravisor: Restrict LDBAR access
Date: Fri, 7 Jun 2019 10:18:29 +0530	[thread overview]
Message-ID: <be82d6c0-826b-a8e8-8d8c-2518404e33a7@linux.vnet.ibm.com> (raw)
In-Reply-To: <20190606173614.32090-8-cclaudio@linux.ibm.com>

On 06/06/19 11:06 PM, 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>
> Signed-off-by: Ram Pai <linuxram@us.ibm.com>
> ---
>   arch/powerpc/kvm/book3s_hv_rmhandlers.S   | 2 ++
>   arch/powerpc/platforms/powernv/idle.c     | 6 ++++--
>   arch/powerpc/platforms/powernv/opal-imc.c | 7 +++++++
>   3 files changed, 13 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 c9133f7908ca..fd62435e3267 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..e9b641d313fb 100644
> --- a/arch/powerpc/platforms/powernv/opal-imc.c
> +++ b/arch/powerpc/platforms/powernv/opal-imc.c
> @@ -254,6 +254,13 @@ static int opal_imc_counters_probe(struct platform_device *pdev)
>   	bool core_imc_reg = false, thread_imc_reg = false;
>   	u32 type;
>
> +	/*
> +	 * When the Ultravisor is enabled, it is responsible for thread-imc
> +	 * updates
> +	 */

Would prefer the comment to be "Disable IMC devices, when Ultravisor is 
enabled"
Rest looks good.
Acked-by: Madhavan Srinivasan <maddy@linux.vnet.ibm.com>

> +	if (firmware_has_feature(FW_FEATURE_ULTRAVISOR))
> +		return -EACCES;
> +
>   	/*
>   	 * Check whether this is kdump kernel. If yes, force the engines to
>   	 * stop and return.