Subject: Re: [PATCH 6/9] iommu/arm-smmu-v3: Directly encode simple commands

From: Pranjal Shrivastava <[email-masked]>
Date: Fri, 8 May 2026 11:33:32 +0000

On Fri, May 01, 2026 at 11:29:15AM -0300, Jason Gunthorpe wrote:
> Add make functions to build commands for
> 
>  CMDQ_OP_TLBI_EL2_ALL
>  CMDQ_OP_TLBI_NSNH_ALL
>  CMDQ_OP_CFGI_ALL
>  CMDQ_OP_PREFETCH_CFG
>  CMDQ_OP_CFGI_STE
>  CMDQ_OP_CFGI_CD
>  CMDQ_OP_RESUME
>  CMDQ_OP_PRI_RESP
> 
> Convert all of these call sites to use the make function instead of
> going through arm_smmu_cmdq_build_cmd(). Use a #define so the general
> pattern is always:
> 
>    arm_smmu_cmdq_issue_cmd(smmu, arm_smmu_make_cmd_XX(..));
> 
> Add arm_smmu_cmdq_batch_add_cmd() which takes struct arm_smmu_cmd
> directly to match the new flow.
> 
> Signed-off-by: Jason Gunthorpe <[email-masked]>
> ---
>  drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 213 +++++++-------------
>  drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h | 109 +++++++---
>  2 files changed, 151 insertions(+), 171 deletions(-)
>

[----- >8 ------]

>  
> -static int __arm_smmu_cmdq_issue_cmd(struct arm_smmu_device *smmu,
> -				     struct arm_smmu_cmd *cmd,
> -				     bool sync)
> +static int arm_smmu_cmdq_issue_cmd_p(struct arm_smmu_device *smmu,
> +				     struct arm_smmu_cmd *cmd, bool sync)

Nit: I'm not sure why we need to rename this? We can still define the 
rest of the helpers like:

#define arm_smmu_cmdq_issue_cmd(smmu, cmd)                      \
	({                                                      \
		struct arm_smmu_cmd __cmd = cmd;                \
		__arm_smmu_cmdq_issue_cmd(smmu, &__cmd, false); \
	})

>  {
>  	return arm_smmu_cmdq_issue_cmdlist(
>  		smmu, arm_smmu_get_cmdq(smmu, cmd), cmd, 1, sync);
>  }
>  
> -static int arm_smmu_cmdq_issue_cmd(struct arm_smmu_device *smmu,
> -				   struct arm_smmu_cmd *cmd)
> -{
> -	return __arm_smmu_cmdq_issue_cmd(smmu, cmd, false);
> -}
> +#define arm_smmu_cmdq_issue_cmd(smmu, cmd)                      \
> +	({                                                      \
> +		struct arm_smmu_cmd __cmd = cmd;                \
> +		arm_smmu_cmdq_issue_cmd_p(smmu, &__cmd, false); \
> +	})
> 
> -static int arm_smmu_cmdq_issue_cmd_with_sync(struct arm_smmu_device *smmu,
> -					     struct arm_smmu_cmd *cmd)
> -{
> -	return __arm_smmu_cmdq_issue_cmd(smmu, cmd, true);
> -}
> +#define arm_smmu_cmdq_issue_cmd_with_sync(smmu, cmd)           \
> +	({                                                     \
> +		struct arm_smmu_cmd __cmd = cmd;               \
> +		arm_smmu_cmdq_issue_cmd_p(smmu, &__cmd, true); \
> +	})
>  
>  static void arm_smmu_cmdq_batch_init_cmd(struct arm_smmu_device *smmu,
>  					 struct arm_smmu_cmdq_batch *cmds,
> @@ -962,14 +924,41 @@ static void arm_smmu_cmdq_batch_init(struct arm_smmu_device *smmu,
>  	arm_smmu_cmdq_batch_init_cmd(smmu, cmds, &cmd);
>  }
>  
> +static void arm_smmu_cmdq_batch_add_cmd_p(struct arm_smmu_device *smmu,
> +					  struct arm_smmu_cmdq_batch *cmds,
> +					  struct arm_smmu_cmd *cmd)

Nit: Same here, why not  __arm_smmu_cmdq_batch_add_cmd? I understand
that _p just means we'll aceept ptr.. but the name's kinda wonky.

> +{
> +	bool force_sync = (cmds->num == CMDQ_BATCH_ENTRIES - 1) &&
> +			  (smmu->options & ARM_SMMU_OPT_CMDQ_FORCE_SYNC);
> +	bool unsupported_cmd;
> +
> +	unsupported_cmd = !arm_smmu_cmdq_supports_cmd(cmds->cmdq, cmd);
> +	if (force_sync || unsupported_cmd) {
> +		arm_smmu_cmdq_issue_cmdlist(smmu, cmds->cmdq, cmds->cmds,
> +					    cmds->num, true);
> +		arm_smmu_cmdq_batch_init_cmd(smmu, cmds, cmd);
> +	}
> +
> +	if (cmds->num == CMDQ_BATCH_ENTRIES) {
> +		arm_smmu_cmdq_issue_cmdlist(smmu, cmds->cmdq, cmds->cmds,
> +					    cmds->num, false);
> +		arm_smmu_cmdq_batch_init_cmd(smmu, cmds, cmd);
> +	}
> +
> +	cmds->cmds[cmds->num++] = *cmd;
> +}
> +
> +#define arm_smmu_cmdq_batch_add_cmd(smmu, cmds, cmd)               \
> +	({                                                         \
> +		struct arm_smmu_cmd __cmd = cmd;                   \
> +		arm_smmu_cmdq_batch_add_cmd_p(smmu, cmds, &__cmd); \
> +	})
> +
>

[----- >8 -----]

>  
>  static irqreturn_t arm_smmu_priq_thread(int irq, void *dev)
> @@ -3464,7 +3405,7 @@ static void arm_smmu_inv_flush_iotlb_tag(struct arm_smmu_inv *inv)
>  
>  	cmd.opcode = inv->nsize_opcode;
>  	arm_smmu_cmdq_build_cmd(&hw_cmd, &cmd);
> -	arm_smmu_cmdq_issue_cmd_with_sync(inv->smmu, &hw_cmd);
> +	arm_smmu_cmdq_issue_cmd_with_sync(inv->smmu, hw_cmd);

Nit: are we passing it by value here? This would be a 16-byte stack
copy? As with the macro expansion this looks like:

{
	struct arm_smmu_cmd __cmd = hw_cmd; // <-- Redundant 16-byte copy
	arm_smmu_cmdq_issue_cmd_p(inv->smmu, &__cmd, true);
}

Why not use arm_smmu_cmdq_issue_cmd_p(inv->smmu, &hw_cmd, true) ?
Although, I see this is eventually cleaned up in Patch 9.

>  }
>  
>  /* Should be installed after arm_smmu_install_ste_for_dev() */
> @@ -4827,8 +4768,6 @@ static int arm_smmu_device_reset(struct arm_smmu_device *smmu)
>  {
>  	int ret;
>  	u32 reg, enables;
> -	struct arm_smmu_cmdq_ent ent;

Ah, we remove this unitialized thing here. I guess we should still init
it in the previous patch for consistency.

[---- >8 ----]

>  #define CMDQ_RESUME_0_RESP_TERM		0UL
>  #define CMDQ_RESUME_0_RESP_RETRY	1UL
>  #define CMDQ_RESUME_0_RESP_ABORT	2UL
> @@ -475,6 +481,77 @@ enum arm_smmu_cmdq_opcode {
>  	CMDQ_OP_CMD_SYNC = 0x46,
>  };
>  
> +static inline struct arm_smmu_cmd
> +arm_smmu_make_cmd_op(enum arm_smmu_cmdq_opcode op)
> +{
> +	struct arm_smmu_cmd cmd = {};
> +
> +	cmd.data[0] = FIELD_PREP(CMDQ_0_OP, op);
> +	return cmd;
> +}
> +
> +static inline struct arm_smmu_cmd arm_smmu_make_cmd_cfgi_all(void)
> +{
> +	struct arm_smmu_cmd cmd = arm_smmu_make_cmd_op(CMDQ_OP_CFGI_ALL);
> +
> +	cmd.data[1] |= FIELD_PREP(CMDQ_CFGI_1_RANGE, 31);

Maybe this is a good opportunity to define "31"? We already have a 
similar definition for TLBI: #define CMDQ_TLBI_RANGE_NUM_MAX 31

Perhaps we could have: #define CMDQ_CFGI_RANGE_ALL 31

With the above nits:

Reviewed-by: Pranjal Shrivastava <[email-masked]>

Thanks,
Praan