Re: [PATCH v5 04/17] powerpc/vas: Add platform specific user window operations

[Nicholas Piggin <npiggin@gmail.com>]

Excerpts from Haren Myneni's message of June 13, 2021 8:57 pm:
> 
> PowerNV uses registers to open/close VAS windows, and getting the
> paste address. Whereas the hypervisor calls are used on PowerVM.
> 
> This patch adds the platform specific user space window operations
> and register with the common VAS user space interface.
> 
> Signed-off-by: Haren Myneni <haren@linux.ibm.com>
> ---
>  arch/powerpc/include/asm/vas.h              | 14 +++++-
>  arch/powerpc/platforms/book3s/vas-api.c     | 53 +++++++++++++--------
>  arch/powerpc/platforms/powernv/vas-window.c | 45 ++++++++++++++++-
>  3 files changed, 89 insertions(+), 23 deletions(-)
> 
> diff --git a/arch/powerpc/include/asm/vas.h b/arch/powerpc/include/asm/vas.h
> index bab7891d43f5..85318d7446c7 100644
> --- a/arch/powerpc/include/asm/vas.h
> +++ b/arch/powerpc/include/asm/vas.h
> @@ -5,6 +5,7 @@
>  
>  #ifndef _ASM_POWERPC_VAS_H
>  #define _ASM_POWERPC_VAS_H
> +#include <uapi/asm/vas-api.h>
>  
>  struct vas_window;
>  
> @@ -48,6 +49,16 @@ enum vas_cop_type {
>  	VAS_COP_TYPE_MAX,
>  };
>  
> +/*
> + * User space window operations used for powernv and powerVM
> + */
> +struct vas_user_win_ops {
> +	struct vas_window * (*open_win)(struct vas_tx_win_open_attr *,
> +				enum vas_cop_type);
> +	u64 (*paste_addr)(struct vas_window *);
> +	int (*close_win)(struct vas_window *);
> +};

This looks better, but rather than pull in uapi and the user API 
structure here, could you just pass in vas_id and flags after the common 
code does the user copy and verifies the version and other details?

I think it's generally good practice to limit the data that the usre
can influence as much as possible. Sorry for not picking up on that
earlier.

If that's changed, then

Reviewed-by: Nicholas Piggin <npiggin@gmail.com>

Thanks,
Nick

> +
>  /*
>   * Receive window attributes specified by the (in-kernel) owner of window.
>   */
> @@ -175,7 +186,8 @@ void vas_unregister_api_powernv(void);
>   * used for others in future.
>   */
>  int vas_register_coproc_api(struct module *mod, enum vas_cop_type cop_type,
> -				const char *name);
> +			    const char *name,
> +			    const struct vas_user_win_ops *vops);
>  void vas_unregister_coproc_api(void);
>  
>  #endif /* __ASM_POWERPC_VAS_H */
> diff --git a/arch/powerpc/platforms/book3s/vas-api.c b/arch/powerpc/platforms/book3s/vas-api.c
> index 72c126d87216..7cfc4b435ae8 100644
> --- a/arch/powerpc/platforms/book3s/vas-api.c
> +++ b/arch/powerpc/platforms/book3s/vas-api.c
> @@ -42,6 +42,7 @@ static struct coproc_dev {
>  	dev_t devt;
>  	struct class *class;
>  	enum vas_cop_type cop_type;
> +	const struct vas_user_win_ops *vops;
>  } coproc_device;
>  
>  struct coproc_instance {
> @@ -72,11 +73,10 @@ static int coproc_open(struct inode *inode, struct file *fp)
>  static int coproc_ioc_tx_win_open(struct file *fp, unsigned long arg)
>  {
>  	void __user *uptr = (void __user *)arg;
> -	struct vas_tx_win_attr txattr = {};
>  	struct vas_tx_win_open_attr uattr;
>  	struct coproc_instance *cp_inst;
>  	struct vas_window *txwin;
> -	int rc, vasid;
> +	int rc;
>  
>  	cp_inst = fp->private_data;
>  
> @@ -93,27 +93,20 @@ static int coproc_ioc_tx_win_open(struct file *fp, unsigned long arg)
>  	}
>  
>  	if (uattr.version != 1) {
> -		pr_err("Invalid version\n");
> +		pr_err("Invalid window open API version\n");
>  		return -EINVAL;
>  	}
>  
> -	vasid = uattr.vas_id;
> -
> -	vas_init_tx_win_attr(&txattr, cp_inst->coproc->cop_type);
> -
> -	txattr.lpid = mfspr(SPRN_LPID);
> -	txattr.pidr = mfspr(SPRN_PID);
> -	txattr.user_win = true;
> -	txattr.rsvd_txbuf_count = false;
> -	txattr.pswid = false;
> -
> -	pr_devel("Pid %d: Opening txwin, PIDR %ld\n", txattr.pidr,
> -				mfspr(SPRN_PID));
> +	if (!cp_inst->coproc->vops && !cp_inst->coproc->vops->open_win) {
> +		pr_err("VAS API is not registered\n");
> +		return -EACCES;
> +	}
>  
> -	txwin = vas_tx_win_open(vasid, cp_inst->coproc->cop_type, &txattr);
> +	txwin = cp_inst->coproc->vops->open_win(&uattr,
> +						cp_inst->coproc->cop_type);
>  	if (IS_ERR(txwin)) {
> -		pr_err("%s() vas_tx_win_open() failed, %ld\n", __func__,
> -					PTR_ERR(txwin));
> +		pr_err("%s() VAS window open failed, %ld\n", __func__,
> +				PTR_ERR(txwin));
>  		return PTR_ERR(txwin);
>  	}
>  
> @@ -125,9 +118,15 @@ static int coproc_ioc_tx_win_open(struct file *fp, unsigned long arg)
>  static int coproc_release(struct inode *inode, struct file *fp)
>  {
>  	struct coproc_instance *cp_inst = fp->private_data;
> +	int rc;
>  
>  	if (cp_inst->txwin) {
> -		vas_win_close(cp_inst->txwin);
> +		if (cp_inst->coproc->vops &&
> +			cp_inst->coproc->vops->close_win) {
> +			rc = cp_inst->coproc->vops->close_win(cp_inst->txwin);
> +			if (rc)
> +				return rc;
> +		}
>  		cp_inst->txwin = NULL;
>  	}
>  
> @@ -168,7 +167,17 @@ static int coproc_mmap(struct file *fp, struct vm_area_struct *vma)
>  		return -EINVAL;
>  	}
>  
> -	vas_win_paste_addr(txwin, &paste_addr, NULL);
> +	if (!cp_inst->coproc->vops && !cp_inst->coproc->vops->paste_addr) {
> +		pr_err("%s(): VAS API is not registered\n", __func__);
> +		return -EACCES;
> +	}
> +
> +	paste_addr = cp_inst->coproc->vops->paste_addr(txwin);
> +	if (!paste_addr) {
> +		pr_err("%s(): Window paste address failed\n", __func__);
> +		return -EINVAL;
> +	}
> +
>  	pfn = paste_addr >> PAGE_SHIFT;
>  
>  	/* flags, page_prot from cxl_mmap(), except we want cachable */
> @@ -208,7 +217,8 @@ static struct file_operations coproc_fops = {
>   * extended to other coprocessor types later.
>   */
>  int vas_register_coproc_api(struct module *mod, enum vas_cop_type cop_type,
> -				const char *name)
> +			    const char *name,
> +			    const struct vas_user_win_ops *vops)
>  {
>  	int rc = -EINVAL;
>  	dev_t devno;
> @@ -230,6 +240,7 @@ int vas_register_coproc_api(struct module *mod, enum vas_cop_type cop_type,
>  	}
>  	coproc_device.class->devnode = coproc_devnode;
>  	coproc_device.cop_type = cop_type;
> +	coproc_device.vops = vops;
>  
>  	coproc_fops.owner = mod;
>  	cdev_init(&coproc_device.cdev, &coproc_fops);
> diff --git a/arch/powerpc/platforms/powernv/vas-window.c b/arch/powerpc/platforms/powernv/vas-window.c
> index 41712b4b268e..5162e95c4090 100644
> --- a/arch/powerpc/platforms/powernv/vas-window.c
> +++ b/arch/powerpc/platforms/powernv/vas-window.c
> @@ -16,6 +16,7 @@
>  #include <linux/mmu_context.h>
>  #include <asm/switch_to.h>
>  #include <asm/ppc-opcode.h>
> +#include <asm/vas.h>
>  #include "vas.h"
>  #include "copy-paste.h"
>  
> @@ -1443,6 +1444,48 @@ struct vas_window *vas_pswid_to_window(struct vas_instance *vinst,
>  	return window;
>  }
>  
> +static struct vas_window *vas_user_win_open(struct vas_tx_win_open_attr *uattr,
> +				enum vas_cop_type cop_type)
> +{
> +	struct vas_tx_win_attr txattr = {};
> +
> +	vas_init_tx_win_attr(&txattr, cop_type);
> +
> +	txattr.lpid = mfspr(SPRN_LPID);
> +	txattr.pidr = mfspr(SPRN_PID);
> +	txattr.user_win = true;
> +	txattr.rsvd_txbuf_count = false;
> +	txattr.pswid = false;
> +
> +	pr_devel("Pid %d: Opening txwin, PIDR %ld\n", txattr.pidr,
> +				mfspr(SPRN_PID));
> +
> +	return vas_tx_win_open(uattr->vas_id, cop_type, &txattr);
> +}
> +
> +static u64 vas_user_win_paste_addr(struct vas_window *win)
> +{
> +	u64 paste_addr;
> +
> +	vas_win_paste_addr(win, &paste_addr, NULL);
> +
> +	return paste_addr;
> +}
> +
> +static int vas_user_win_close(struct vas_window *txwin)
> +{
> +
> +	vas_win_close(txwin);
> +
> +	return 0;
> +}
> +
> +static const struct vas_user_win_ops vops =  {
> +	.open_win	=	vas_user_win_open,
> +	.paste_addr	=	vas_user_win_paste_addr,
> +	.close_win	=	vas_user_win_close,
> +};
> +
>  /*
>   * Supporting only nx-gzip coprocessor type now, but this API code
>   * extended to other coprocessor types later.
> @@ -1451,7 +1494,7 @@ int vas_register_api_powernv(struct module *mod, enum vas_cop_type cop_type,
>  			     const char *name)
>  {
>  
> -	return vas_register_coproc_api(mod, cop_type, name);
> +	return vas_register_coproc_api(mod, cop_type, name, &vops);
>  }
>  EXPORT_SYMBOL_GPL(vas_register_api_powernv);
>  
> -- 
> 2.18.2
> 
> 
>