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s390/sthyi: add cache to store hypervisor info

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STHYI requires extensive locking in the higher hypervisors and is
very computational/memory expensive. Therefore we cache the retrieved
hypervisor info whose valid period is 1s with mutex to allow concurrent
access. rw semaphore can't benefit here due to cache line bounce.

Signed-off-by: QingFeng Hao <haoqf@linux.vnet.ibm.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
This commit is contained in:
QingFeng Hao
2017-09-29 12:41:51 +02:00
committed by Martin Schwidefsky
parent b7c92f1a4e
commit 9fb6c9b3fe
4 changed files with 71 additions and 26 deletions
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84
arch/s390/kernel/sthyi.c
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@@ -11,7 +11,6 @@
#include <linux/errno.h>
#include <linux/pagemap.h>
#include <linux/vmalloc.h>
#include <linux/ratelimit.h>
#include <asm/asm-offsets.h>
#include <asm/sclp.h>
@@ -139,6 +138,21 @@ struct lpar_cpu_inf {
struct cpu_inf ifl;
};
/*
* STHYI requires extensive locking in the higher hypervisors
* and is very computational/memory expensive. Therefore we
* cache the retrieved data whose valid period is 1s.
*/
#define CACHE_VALID_JIFFIES HZ
struct sthyi_info {
void *info;
unsigned long end;
};
static DEFINE_MUTEX(sthyi_mutex);
static struct sthyi_info sthyi_cache;
static inline u64 cpu_id(u8 ctidx, void *diag224_buf)
{
return *((u64 *)(diag224_buf + (ctidx + 1) * DIAG204_CPU_NAME_LEN));
@@ -395,6 +409,47 @@ static int sthyi(u64 vaddr, u64 *rc)
return cc;
}
static int fill_dst(void *dst, u64 *rc)
{
struct sthyi_sctns *sctns = (struct sthyi_sctns *)dst;
/*
* If the facility is on, we don't want to emulate the instruction.
* We ask the hypervisor to provide the data.
*/
if (test_facility(74))
return sthyi((u64)dst, rc);
fill_hdr(sctns);
fill_stsi(sctns);
fill_diag(sctns);
*rc = 0;
return 0;
}
static int sthyi_init_cache(void)
{
if (sthyi_cache.info)
return 0;
sthyi_cache.info = (void *)get_zeroed_page(GFP_KERNEL);
if (!sthyi_cache.info)
return -ENOMEM;
sthyi_cache.end = jiffies - 1; /* expired */
return 0;
}
static int sthyi_update_cache(u64 *rc)
{
int r;
memset(sthyi_cache.info, 0, PAGE_SIZE);
r = fill_dst(sthyi_cache.info, rc);
if (r)
return r;
sthyi_cache.end = jiffies + CACHE_VALID_JIFFIES;
return r;
}
/*
* sthyi_fill - Fill page with data returned by the STHYI instruction
*
@@ -409,20 +464,23 @@ static int sthyi(u64 vaddr, u64 *rc)
*/
int sthyi_fill(void *dst, u64 *rc)
{
struct sthyi_sctns *sctns = (struct sthyi_sctns *)dst;
int r;
/*
* If the facility is on, we don't want to emulate the instruction.
* We ask the hypervisor to provide the data.
*/
if (test_facility(74))
return sthyi((u64)dst, rc);
fill_hdr(sctns);
fill_stsi(sctns);
fill_diag(sctns);
mutex_lock(&sthyi_mutex);
r = sthyi_init_cache();
if (r)
goto out;
if (time_is_before_jiffies(sthyi_cache.end)) {
/* cache expired */
r = sthyi_update_cache(rc);
if (r)
goto out;
}
*rc = 0;
return 0;
memcpy(dst, sthyi_cache.info, PAGE_SIZE);
out:
mutex_unlock(&sthyi_mutex);
return r;
}
EXPORT_SYMBOL_GPL(sthyi_fill);