linux-kernel - Re: [PATCH v2] iommu/arm-smmu-v3: Avoid ILLEGAL setting of STE.S1STALLD and CD.S

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Message-ID: <7eb1db90-9a30-b70c-c3d1-71bbca41502d@huawei.com>
Date:   Fri, 20 Oct 2017 15:00:01 +0800
From:   Yisheng Xie <xieyisheng1@...wei.com>
To:     <will.deacon@....com>, <jean-philippe.brucker@....com>,
        <robin.murphy@....com>, <joro@...tes.org>
CC:     <linux-arm-kernel@...ts.infradead.org>,
        <iommu@...ts.linux-foundation.org>, <linux-kernel@...r.kernel.org>,
        <liubo95@...wei.com>, <chenjiankang1@...wei.com>
Subject: Re: [PATCH v2] iommu/arm-smmu-v3: Avoid ILLEGAL setting of
 STE.S1STALLD and CD.S

Hi Will & Jean,

Any comment about this version?

Thanks
Yisheng Xie

On 2017/9/21 20:36, Yisheng Xie wrote:
> According to Spec, it is ILLEGAL to set STE.S1STALLD if STALL_MODEL
> is not 0b00, which means we should not disable stall mode if stall
> or terminate mode is not configuable.
> 
> Meanwhile, it is also ILLEGAL when STALL_MODEL==0b10 && CD.S==0 which
> means if stall mode is force we should always set CD.S.
> 
> As Jean-Philippe's suggestion, this patch introduce a feature bit
> ARM_SMMU_FEAT_STALL_FORCE, which means smmu only supports stall force.
> Therefore, we can avoid the ILLEGAL setting of STE.S1STALLD.by checking
> ARM_SMMU_FEAT_STALL_FORCE.
> 
> This patch keeps the ARM_SMMU_FEAT_STALLS as the meaning of stall supported
> (force or configuable) to easy to expand the future function, i.e. we can
> only use ARM_SMMU_FEAT_STALLS to check whether we should register fault
> handle or enable master can_stall, etc to supporte platform SVM.
> 
> The feature bit, STE.S1STALLD and CD.S setting will be like:
> 
> STALL_MODEL  FEATURE                                         S1STALLD CD.S
> 0b00         ARM_SMMU_FEAT_STALLS                                 0b1 0b0
> 0b01         !ARM_SMMU_FEAT_STALLS && !ARM_SMMU_FEAT_STALL_FORCE  0b0 0b0
> 0b10         ARM_SMMU_FEAT_STALLS && ARM_SMMU_FEAT_STALL_FORCE    0b0 0b1
> 
> after apply this patch.
> 
> Signed-off-by: Yisheng Xie <xieyisheng1@...wei.com>
> ---
> v2:
>  * Keep the feature bits backward compatible and add new one at the end
>  * Avoid ILLEGAL of CD.S - both as Jean's suggestion.
> 
>  drivers/iommu/arm-smmu-v3.c | 15 ++++++++++++---
>  1 file changed, 12 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/iommu/arm-smmu-v3.c b/drivers/iommu/arm-smmu-v3.c
> index e67ba6c..22a6b08 100644
> --- a/drivers/iommu/arm-smmu-v3.c
> +++ b/drivers/iommu/arm-smmu-v3.c
> @@ -316,6 +316,7 @@
>  #define ARM64_TCR_TBI0_MASK		0x1UL
>  
>  #define CTXDESC_CD_0_AA64		(1UL << 41)
> +#define CTXDESC_CD_0_S			(1UL << 44)
>  #define CTXDESC_CD_0_R			(1UL << 45)
>  #define CTXDESC_CD_0_A			(1UL << 46)
>  #define CTXDESC_CD_0_ASET_SHIFT		47
> @@ -604,6 +605,7 @@ struct arm_smmu_device {
>  #define ARM_SMMU_FEAT_TRANS_S2		(1 << 10)
>  #define ARM_SMMU_FEAT_STALLS		(1 << 11)
>  #define ARM_SMMU_FEAT_HYP		(1 << 12)
> +#define ARM_SMMU_FEAT_STALL_FORCE	(1 << 13)
>  	u32				features;
>  
>  #define ARM_SMMU_OPT_SKIP_PREFETCH	(1 << 0)
> @@ -996,6 +998,11 @@ static void arm_smmu_write_ctx_desc(struct arm_smmu_device *smmu,
>  	      CTXDESC_CD_0_R | CTXDESC_CD_0_A | CTXDESC_CD_0_ASET_PRIVATE |
>  	      CTXDESC_CD_0_AA64 | (u64)cfg->cd.asid << CTXDESC_CD_0_ASID_SHIFT |
>  	      CTXDESC_CD_0_V;
> +
> +	/* STALL_MODEL==0b10 && CD.S==0 is ILLEGAL */
> +	if (smmu->features & ARM_SMMU_FEAT_STALL_FORCE)
> +		val |= CTXDESC_CD_0_S;
> +
>  	cfg->cdptr[0] = cpu_to_le64(val);
>  
>  	val = cfg->cd.ttbr & CTXDESC_CD_1_TTB0_MASK << CTXDESC_CD_1_TTB0_SHIFT;
> @@ -1112,7 +1119,8 @@ static void arm_smmu_write_strtab_ent(struct arm_smmu_device *smmu, u32 sid,
>  #endif
>  			 STRTAB_STE_1_STRW_NSEL1 << STRTAB_STE_1_STRW_SHIFT);
>  
> -		if (smmu->features & ARM_SMMU_FEAT_STALLS)
> +		if (smmu->features & ARM_SMMU_FEAT_STALLS &&
> +		   !(smmu->features & ARM_SMMU_FEAT_STALL_FORCE))
>  			dst[1] |= cpu_to_le64(STRTAB_STE_1_S1STALLD);
>  
>  		val |= (ste->s1_cfg->cdptr_dma & STRTAB_STE_0_S1CTXPTR_MASK
> @@ -2536,9 +2544,10 @@ static int arm_smmu_device_hw_probe(struct arm_smmu_device *smmu)
>  			 coherent ? "true" : "false");
>  
>  	switch (reg & IDR0_STALL_MODEL_MASK << IDR0_STALL_MODEL_SHIFT) {
> -	case IDR0_STALL_MODEL_STALL:
> -		/* Fallthrough */
>  	case IDR0_STALL_MODEL_FORCE:
> +		smmu->features |= ARM_SMMU_FEAT_STALL_FORCE;
> +		/* Fallthrough */
> +	case IDR0_STALL_MODEL_STALL:
>  		smmu->features |= ARM_SMMU_FEAT_STALLS;
>  	}
>  
>