2023-02-02 15:31:29

by Peter Zijlstra

Subject: [PATCH v2 10/10] s390/cpum_sf: Convert to cmpxchg128()

Now that there is a cross arch u128 and cmpxchg128(), use those
instead of the custom CDSG helper.

Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
---
arch/s390/include/asm/cpu_mf.h | 2 +-
arch/s390/kernel/perf_cpum_sf.c | 22 ++++++----------------
2 files changed, 7 insertions(+), 17 deletions(-)

--- a/arch/s390/include/asm/cpu_mf.h
+++ b/arch/s390/include/asm/cpu_mf.h
@@ -141,7 +141,7 @@ union hws_trailer_header {
unsigned int dsdes:16; /* 48-63: size of diagnostic SDE */
unsigned long long overflow; /* 64 - Overflow Count */
};
- __uint128_t val;
+ u128 val;
};

struct hws_trailer_entry {
--- a/arch/s390/kernel/perf_cpum_sf.c
+++ b/arch/s390/kernel/perf_cpum_sf.c
@@ -1228,16 +1228,6 @@ static void hw_collect_samples(struct pe
}
}

-static inline __uint128_t __cdsg(__uint128_t *ptr, __uint128_t old, __uint128_t new)
-{
- asm volatile(
- " cdsg %[old],%[new],%[ptr]\n"
- : [old] "+d" (old), [ptr] "+QS" (*ptr)
- : [new] "d" (new)
- : "memory", "cc");
- return old;
-}
-
/* hw_perf_event_update() - Process sampling buffer
* @event: The perf event
* @flush_all: Flag to also flush partially filled sample-data-blocks
@@ -1307,14 +1297,14 @@ static void hw_perf_event_update(struct

/* Reset trailer (using compare-double-and-swap) */
/* READ_ONCE() 16 byte header */
- prev.val = __cdsg(&te->header.val, 0, 0);
+ prev.val = cmpxchg128(&te->header.val, 0, 0);
do {
old.val = prev.val;
new.val = prev.val;
new.f = 0;
new.a = 1;
new.overflow = 0;
- prev.val = __cdsg(&te->header.val, old.val, new.val);
+ prev.val = cmpxchg128(&te->header.val, old.val, new.val);
} while (prev.val != old.val);

/* Advance to next sample-data-block */
@@ -1496,7 +1486,7 @@ static bool aux_set_alert(struct aux_buf

te = aux_sdb_trailer(aux, alert_index);
/* READ_ONCE() 16 byte header */
- prev.val = __cdsg(&te->header.val, 0, 0);
+ prev.val = cmpxchg128(&te->header.val, 0, 0);
do {
old.val = prev.val;
new.val = prev.val;
@@ -1511,7 +1501,7 @@ static bool aux_set_alert(struct aux_buf
}
new.a = 1;
new.overflow = 0;
- prev.val = __cdsg(&te->header.val, old.val, new.val);
+ prev.val = cmpxchg128(&te->header.val, old.val, new.val);
} while (prev.val != old.val);
return true;
}
@@ -1575,7 +1565,7 @@ static bool aux_reset_buffer(struct aux_
for (i = 0; i < range_scan; i++, idx++) {
te = aux_sdb_trailer(aux, idx);
/* READ_ONCE() 16 byte header */
- prev.val = __cdsg(&te->header.val, 0, 0);
+ prev.val = cmpxchg128(&te->header.val, 0, 0);
do {
old.val = prev.val;
new.val = prev.val;
@@ -1586,7 +1576,7 @@ static bool aux_reset_buffer(struct aux_
new.a = 1;
else
new.a = 0;
- prev.val = __cdsg(&te->header.val, old.val, new.val);
+ prev.val = cmpxchg128(&te->header.val, old.val, new.val);
} while (prev.val != old.val);
*overflow += orig_overflow;
}

2023-02-02 17:06:50

by Heiko Carstens

Subject: Re: [PATCH v2 10/10] s390/cpum_sf: Convert to cmpxchg128()

On Thu, Feb 02, 2023 at 03:50:40PM +0100, Peter Zijlstra wrote:
> Now that there is a cross arch u128 and cmpxchg128(), use those
> instead of the custom CDSG helper.
>
> Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
> ---
> arch/s390/include/asm/cpu_mf.h | 2 +-
> arch/s390/kernel/perf_cpum_sf.c | 22 ++++++----------------
> 2 files changed, 7 insertions(+), 17 deletions(-)

Acked-by: Heiko Carstens <[email protected]>