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

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

[Aneesh Kumar K.V]

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);
+	return 0;
+}
+late_initcall(create_tlb_single_page_flush_ceiling);
+
-- 
2.31.1

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

[Christophe Leroy]

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);
> +
> 

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

[Michael Ellerman]

Christophe Leroy <christophe.leroy@csgroup.eu> writes:
> 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 @@
...
>> +
>> +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 ?

Yeah AFAICS that should work fine.

It could probably even be a u16?

cheers

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

[Aneesh Kumar K.V]

On 8/12/21 12:58 PM, Michael Ellerman wrote:
> Christophe Leroy <christophe.leroy@csgroup.eu> writes:
>> 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 @@
> ...
>>> +
>>> +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 ?
> 
> Yeah AFAICS that should work fine.
> 
> It could probably even be a u16?
> 

I was looking at switching all that to u64. Should i fallback to u16, 
considering a tlb_signle_page_flush_ceiling value larger that 2**16 
doesn't make sense?

-aneesh

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

[Michael Ellerman]

"Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com> writes:
> On 8/12/21 12:58 PM, Michael Ellerman wrote:
>> Christophe Leroy <christophe.leroy@csgroup.eu> writes:
>>> 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 @@
>> ...
>>>> +
>>>> +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 ?
>> 
>> Yeah AFAICS that should work fine.
>> 
>> It could probably even be a u16?
>
> I was looking at switching all that to u64. Should i fallback to u16, 
> considering a tlb_signle_page_flush_ceiling value larger that 2**16 
> doesn't make sense?

Hmm, if we make it u16 and someone writes a value >= 2^16 it just
truncates the value to 0, which is a bit unfortunate.

So maybe just make it u32, that way if someone writes a stupidly large
value it stays large.

cheers