Re: [PATCH] scsi: libsas: Add SMP request allocation handler callback

[Damien Le Moal <dlemoal@kernel.org>]

On 3/25/24 22:17, Yihang Li wrote:
> This series [1] reducing the kmalloc() minimum alignment on arm64 to 8
> (from 128).

And ? What is the point you are trying to convey here ?

> The hisi_sas has special requirements on the memory address alignment
> (must be 16-byte-aligned) of the command request frame, so add a SMP
> request allocation callback and fill it in for the hisi_sas driver.

128 is aligned to 16. So what is the problem you are trying to solve here ?
Can you clarify ? I suspect this is all about memory allocation optimization ?

> 
> Link: https://lkml.kernel.org/r/20230612153201.554742-1-catalin.marinas@arm.com [1]
> Signed-off-by: Yihang Li <liyihang9@huawei.com>
> ---
>  drivers/scsi/hisi_sas/hisi_sas_main.c | 14 ++++++++++++
>  drivers/scsi/libsas/sas_expander.c    | 31 ++++++++++++++++++---------
>  include/scsi/libsas.h                 |  3 +++
>  3 files changed, 38 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/scsi/hisi_sas/hisi_sas_main.c b/drivers/scsi/hisi_sas/hisi_sas_main.c
> index 097dfe4b620d..40329558d435 100644
> --- a/drivers/scsi/hisi_sas/hisi_sas_main.c
> +++ b/drivers/scsi/hisi_sas/hisi_sas_main.c
> @@ -2031,6 +2031,19 @@ static int hisi_sas_write_gpio(struct sas_ha_struct *sha, u8 reg_type,
>  				reg_index, reg_count, write_data);
>  }
>  
> +static void *hisi_sas_alloc_smp_req(int size)
> +{
> +	u8 *p;
> +
> +	/* The address must be 16-byte-aligned. */

ARCH_DMA_MINALIGN is not always 16, right ?

> +	size = ALIGN(size, ARCH_DMA_MINALIGN);
> +	p = kzalloc(size, GFP_KERNEL);
> +	if (p)
> +		p[0] = SMP_REQUEST;
> +
> +	return p;
> +}
> +
>  static void hisi_sas_phy_disconnected(struct hisi_sas_phy *phy)
>  {
>  	struct asd_sas_phy *sas_phy = &phy->sas_phy;
> @@ -2130,6 +2143,7 @@ static struct sas_domain_function_template hisi_sas_transport_ops = {
>  	.lldd_write_gpio	= hisi_sas_write_gpio,
>  	.lldd_tmf_aborted	= hisi_sas_tmf_aborted,
>  	.lldd_abort_timeout	= hisi_sas_internal_abort_timeout,
> +	.lldd_alloc_smp_req	= hisi_sas_alloc_smp_req,

Why this complexity ? Why not simply modify alloc_smp_req() to have the required
alignment ? This will avoid a costly indirect function call.

>  };
>  
>  void hisi_sas_init_mem(struct hisi_hba *hisi_hba)
> diff --git a/drivers/scsi/libsas/sas_expander.c b/drivers/scsi/libsas/sas_expander.c
> index a2204674b680..0fd0507f7fc6 100644
> --- a/drivers/scsi/libsas/sas_expander.c
> +++ b/drivers/scsi/libsas/sas_expander.c
> @@ -141,6 +141,17 @@ static inline void *alloc_smp_req(int size)
>  	return p;
>  }
>  
> +static void *sas_alloc_smp_req(struct domain_device *dev, int size)
> +{
> +	struct sas_internal *i =
> +		to_sas_internal(dev->port->ha->shost->transportt);
> +
> +	if (i->dft->lldd_alloc_smp_req)
> +		return i->dft->lldd_alloc_smp_req(size);
> +
> +	return alloc_smp_req(size);
> +}
> +
>  static inline void *alloc_smp_resp(int size)
>  {
>  	return kzalloc(size, GFP_KERNEL);
> @@ -377,7 +388,7 @@ int sas_ex_phy_discover(struct domain_device *dev, int single)
>  	u8   *disc_req;
>  	struct smp_disc_resp *disc_resp;
>  
> -	disc_req = alloc_smp_req(DISCOVER_REQ_SIZE);
> +	disc_req = sas_alloc_smp_req(dev, DISCOVER_REQ_SIZE);
>  	if (!disc_req)
>  		return -ENOMEM;
>  
> @@ -440,7 +451,7 @@ static int sas_ex_general(struct domain_device *dev)
>  	int res;
>  	int i;
>  
> -	rg_req = alloc_smp_req(RG_REQ_SIZE);
> +	rg_req = sas_alloc_smp_req(dev, RG_REQ_SIZE);
>  	if (!rg_req)
>  		return -ENOMEM;
>  
> @@ -519,7 +530,7 @@ static int sas_ex_manuf_info(struct domain_device *dev)
>  	u8 *mi_resp;
>  	int res;
>  
> -	mi_req = alloc_smp_req(MI_REQ_SIZE);
> +	mi_req = sas_alloc_smp_req(dev, MI_REQ_SIZE);
>  	if (!mi_req)
>  		return -ENOMEM;
>  
> @@ -560,7 +571,7 @@ int sas_smp_phy_control(struct domain_device *dev, int phy_id,
>  	u8 *pc_resp;
>  	int res;
>  
> -	pc_req = alloc_smp_req(PC_REQ_SIZE);
> +	pc_req = sas_alloc_smp_req(dev, PC_REQ_SIZE);
>  	if (!pc_req)
>  		return -ENOMEM;
>  
> @@ -642,7 +653,7 @@ int sas_smp_get_phy_events(struct sas_phy *phy)
>  	struct sas_rphy *rphy = dev_to_rphy(phy->dev.parent);
>  	struct domain_device *dev = sas_find_dev_by_rphy(rphy);
>  
> -	req = alloc_smp_req(RPEL_REQ_SIZE);
> +	req = sas_alloc_smp_req(dev, RPEL_REQ_SIZE);
>  	if (!req)
>  		return -ENOMEM;
>  
> @@ -682,7 +693,7 @@ int sas_get_report_phy_sata(struct domain_device *dev, int phy_id,
>  			    struct smp_rps_resp *rps_resp)
>  {
>  	int res;
> -	u8 *rps_req = alloc_smp_req(RPS_REQ_SIZE);
> +	u8 *rps_req = sas_alloc_smp_req(dev, RPS_REQ_SIZE);
>  	u8 *resp = (u8 *)rps_resp;
>  
>  	if (!rps_req)
> @@ -1344,7 +1355,7 @@ static int sas_configure_present(struct domain_device *dev, int phy_id,
>  	*present = 0;
>  	*index = 0;
>  
> -	rri_req = alloc_smp_req(RRI_REQ_SIZE);
> +	rri_req = sas_alloc_smp_req(dev, RRI_REQ_SIZE);
>  	if (!rri_req)
>  		return -ENOMEM;
>  
> @@ -1412,7 +1423,7 @@ static int sas_configure_set(struct domain_device *dev, int phy_id,
>  	u8 *cri_req;
>  	u8 *cri_resp;
>  
> -	cri_req = alloc_smp_req(CRI_REQ_SIZE);
> +	cri_req = sas_alloc_smp_req(dev, CRI_REQ_SIZE);
>  	if (!cri_req)
>  		return -ENOMEM;
>  
> @@ -1627,7 +1638,7 @@ static int sas_get_phy_discover(struct domain_device *dev,
>  	int res;
>  	u8 *disc_req;
>  
> -	disc_req = alloc_smp_req(DISCOVER_REQ_SIZE);
> +	disc_req = sas_alloc_smp_req(dev, DISCOVER_REQ_SIZE);
>  	if (!disc_req)
>  		return -ENOMEM;
>  
> @@ -1723,7 +1734,7 @@ static int sas_get_ex_change_count(struct domain_device *dev, int *ecc)
>  	u8  *rg_req;
>  	struct smp_rg_resp  *rg_resp;
>  
> -	rg_req = alloc_smp_req(RG_REQ_SIZE);
> +	rg_req = sas_alloc_smp_req(dev, RG_REQ_SIZE);
>  	if (!rg_req)
>  		return -ENOMEM;
>  
> diff --git a/include/scsi/libsas.h b/include/scsi/libsas.h
> index f5257103fdb6..2e6e5f6e50db 100644
> --- a/include/scsi/libsas.h
> +++ b/include/scsi/libsas.h
> @@ -670,6 +670,9 @@ struct sas_domain_function_template {
>  	/* GPIO support */
>  	int (*lldd_write_gpio)(struct sas_ha_struct *, u8 reg_type,
>  			       u8 reg_index, u8 reg_count, u8 *write_data);
> +
> +	/* Allocation for SMP request */
> +	void *(*lldd_alloc_smp_req)(int size);
>  };
>  
>  extern int sas_register_ha(struct sas_ha_struct *);

-- 
Damien Le Moal
Western Digital Research