Re: [PATCH] powerpc/book3s64/radix: make tlb_single_page_flush_ceiling a debugfs entry

[Christophe Leroy <christophe.leroy@csgroup.eu>]

Le 10/08/2021 à 06:53, Aneesh Kumar K.V a écrit :
> Similar to x86/s390 add a debugfs file to tune tlb_single_page_flush_ceiling.
> 
> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
> ---
>   arch/powerpc/mm/book3s64/radix_tlb.c | 48 ++++++++++++++++++++++++++++
>   1 file changed, 48 insertions(+)
> 
> diff --git a/arch/powerpc/mm/book3s64/radix_tlb.c b/arch/powerpc/mm/book3s64/radix_tlb.c
> index aefc100d79a7..5cca0fe130e7 100644
> --- a/arch/powerpc/mm/book3s64/radix_tlb.c
> +++ b/arch/powerpc/mm/book3s64/radix_tlb.c
> @@ -17,6 +17,7 @@
>   #include <asm/trace.h>
>   #include <asm/cputhreads.h>
>   #include <asm/plpar_wrappers.h>
> +#include <asm/debugfs.h>
>   
>   #include "internal.h"
>   
> @@ -1524,3 +1525,50 @@ void do_h_rpt_invalidate_prt(unsigned long pid, unsigned long lpid,
>   EXPORT_SYMBOL_GPL(do_h_rpt_invalidate_prt);
>   
>   #endif /* CONFIG_KVM_BOOK3S_HV_POSSIBLE */
> +
> +static ssize_t tlbflush_read_file(struct file *file, char __user *user_buf,
> +			     size_t count, loff_t *ppos)
> +{
> +	char buf[32];
> +	unsigned int len;
> +
> +	len = sprintf(buf, "%ld\n", tlb_single_page_flush_ceiling);
> +	return simple_read_from_buffer(user_buf, count, ppos, buf, len);
> +}
> +
> +static ssize_t tlbflush_write_file(struct file *file,
> +		 const char __user *user_buf, size_t count, loff_t *ppos)
> +{
> +	char buf[32];
> +	ssize_t len;
> +	int ceiling;
> +
> +	len = min(count, sizeof(buf) - 1);
> +	if (copy_from_user(buf, user_buf, len))
> +		return -EFAULT;
> +
> +	buf[len] = '\0';
> +	if (kstrtoint(buf, 0, &ceiling))
> +		return -EINVAL;
> +
> +	if (ceiling < 0)
> +		return -EINVAL;
> +
> +	tlb_single_page_flush_ceiling = ceiling;
> +	return count;
> +}
> +
> +static const struct file_operations fops_tlbflush = {
> +	.read = tlbflush_read_file,
> +	.write = tlbflush_write_file,
> +	.llseek = default_llseek,
> +};
> +
> +static int __init create_tlb_single_page_flush_ceiling(void)
> +{
> +	debugfs_create_file("tlb_single_page_flush_ceiling", S_IRUSR | S_IWUSR,
> +			    powerpc_debugfs_root, NULL, &fops_tlbflush);

Could you just use debugfs_create_u32() instead of re-implementing simple read and write ?

Or at least use DEFINE_DEBUGFS_ATTRIBUTE() if you need something a bit more elaborated ?

> +	return 0;
> +}
> +late_initcall(create_tlb_single_page_flush_ceiling);
> +
>