Re: [PATCH v2 2/5] powerpc: Fix vDSO clock_getres()

Le 21/05/2019 à 18:08, Vincenzo Frascino a écrit :

Hi Christophe,

I did not see this patch in 5.2-rc1 and I was wondering if there is anything I
can do to help with upstraming it.

As far as I can see you series still has status 'new' in patchwork so I 
guess Michael didn't have time to look at it 
(https://patchwork.ozlabs.org/patch/1086410/)

Please let me know.

You series involves several arches, how do you plan to handle it ? Do 
you expect each arch maintainer to take each patch independentely, or do 
you expect acks from arch maintainers in order to merge the entire 
series in a given tree (which one ?)

Christophe

Thanks,
Vincenzo

On 23/04/2019 17:33, Christophe Leroy wrote:

quoted

Le 16/04/2019 à 18:14, Vincenzo Frascino a écrit :

quoted

clock_getres in the vDSO library has to preserve the same behaviour
of posix_get_hrtimer_res().

In particular, posix_get_hrtimer_res() does:
      sec = 0;
      ns = hrtimer_resolution;
and hrtimer_resolution depends on the enablement of the high
resolution timers that can happen either at compile or at run time.

Fix the powerpc vdso implementation of clock_getres keeping a copy of
hrtimer_resolution in vdso data and using that directly.

Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <redacted>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com>

Reviewed-by: Christophe Leroy <redacted>

quoted

---
   arch/powerpc/include/asm/vdso_datapage.h  | 2 ++
   arch/powerpc/kernel/asm-offsets.c         | 2 +-
   arch/powerpc/kernel/time.c                | 1 +
   arch/powerpc/kernel/vdso32/gettimeofday.S | 7 +++++--
   arch/powerpc/kernel/vdso64/gettimeofday.S | 7 +++++--
   5 files changed, 14 insertions(+), 5 deletions(-)

diff --git a/arch/powerpc/include/asm/vdso_datapage.h b/arch/powerpc/include/asm/vdso_datapage.h
index bbc06bd72b1f..4333b9a473dc 100644
--- a/arch/powerpc/include/asm/vdso_datapage.h
+++ b/arch/powerpc/include/asm/vdso_datapage.h

@@ -86,6 +86,7 @@ struct vdso_data {
   	__s32 wtom_clock_nsec;			/* Wall to monotonic clock nsec */
   	__s64 wtom_clock_sec;			/* Wall to monotonic clock sec */
   	struct timespec stamp_xtime;		/* xtime as at tb_orig_stamp */
+	__u32 hrtimer_res;			/* hrtimer resolution */
      	__u32 syscall_map_64[SYSCALL_MAP_SIZE]; /* map of syscalls  */
      	__u32 syscall_map_32[SYSCALL_MAP_SIZE]; /* map of syscalls */
   };

@@ -107,6 +108,7 @@ struct vdso_data {
   	__s32 wtom_clock_nsec;
   	struct timespec stamp_xtime;	/* xtime as at tb_orig_stamp */
   	__u32 stamp_sec_fraction;	/* fractional seconds of stamp_xtime */
+	__u32 hrtimer_res;		/* hrtimer resolution */
      	__u32 syscall_map_32[SYSCALL_MAP_SIZE]; /* map of syscalls */
   	__u32 dcache_block_size;	/* L1 d-cache block size     */
   	__u32 icache_block_size;	/* L1 i-cache block size     */

diff --git a/arch/powerpc/kernel/asm-offsets.c b/arch/powerpc/kernel/asm-offsets.c
index 86a61e5f8285..52e4b98a8492 100644
--- a/arch/powerpc/kernel/asm-offsets.c
+++ b/arch/powerpc/kernel/asm-offsets.c

@@ -383,6 +383,7 @@ int main(void)
   	OFFSET(WTOM_CLOCK_NSEC, vdso_data, wtom_clock_nsec);
   	OFFSET(STAMP_XTIME, vdso_data, stamp_xtime);
   	OFFSET(STAMP_SEC_FRAC, vdso_data, stamp_sec_fraction);
+	OFFSET(CLOCK_REALTIME_RES, vdso_data, hrtimer_res);
   	OFFSET(CFG_ICACHE_BLOCKSZ, vdso_data, icache_block_size);
   	OFFSET(CFG_DCACHE_BLOCKSZ, vdso_data, dcache_block_size);
   	OFFSET(CFG_ICACHE_LOGBLOCKSZ, vdso_data, icache_log_block_size);

@@ -413,7 +414,6 @@ int main(void)
   	DEFINE(CLOCK_REALTIME_COARSE, CLOCK_REALTIME_COARSE);
   	DEFINE(CLOCK_MONOTONIC_COARSE, CLOCK_MONOTONIC_COARSE);
   	DEFINE(NSEC_PER_SEC, NSEC_PER_SEC);
-	DEFINE(CLOCK_REALTIME_RES, MONOTONIC_RES_NSEC);
   
   #ifdef CONFIG_BUG
   	DEFINE(BUG_ENTRY_SIZE, sizeof(struct bug_entry));

diff --git a/arch/powerpc/kernel/time.c b/arch/powerpc/kernel/time.c
index bc0503ef9c9c..62c04a6746d8 100644
--- a/arch/powerpc/kernel/time.c
+++ b/arch/powerpc/kernel/time.c

@@ -955,6 +955,7 @@ void update_vsyscall(struct timekeeper *tk)
   	vdso_data->wtom_clock_nsec = tk->wall_to_monotonic.tv_nsec;
   	vdso_data->stamp_xtime = xt;
   	vdso_data->stamp_sec_fraction = frac_sec;
+	vdso_data->hrtimer_res = hrtimer_resolution;
   	smp_wmb();
   	++(vdso_data->tb_update_count);
   }

diff --git a/arch/powerpc/kernel/vdso32/gettimeofday.S b/arch/powerpc/kernel/vdso32/gettimeofday.S
index afd516b572f8..2b5f9e83c610 100644
--- a/arch/powerpc/kernel/vdso32/gettimeofday.S
+++ b/arch/powerpc/kernel/vdso32/gettimeofday.S

@@ -160,12 +160,15 @@ V_FUNCTION_BEGIN(__kernel_clock_getres)
   	cror	cr0*4+eq,cr0*4+eq,cr1*4+eq
   	bne	cr0,99f
   
+	mflr	r12
+  .cfi_register lr,r12
+	bl	__get_datapage@local
+	lwz	r5,CLOCK_REALTIME_RES(r3)
+	mtlr	r12
   	li	r3,0
   	cmpli	cr0,r4,0
   	crclr	cr0*4+so
   	beqlr
-	lis	r5,CLOCK_REALTIME_RES@h
-	ori	r5,r5,CLOCK_REALTIME_RES@l
   	stw	r3,TSPC32_TV_SEC(r4)
   	stw	r5,TSPC32_TV_NSEC(r4)
   	blr

diff --git a/arch/powerpc/kernel/vdso64/gettimeofday.S b/arch/powerpc/kernel/vdso64/gettimeofday.S
index 1f324c28705b..f07730f73d5e 100644
--- a/arch/powerpc/kernel/vdso64/gettimeofday.S
+++ b/arch/powerpc/kernel/vdso64/gettimeofday.S

@@ -190,12 +190,15 @@ V_FUNCTION_BEGIN(__kernel_clock_getres)
   	cror	cr0*4+eq,cr0*4+eq,cr1*4+eq
   	bne	cr0,99f
   
+	mflr	r12
+  .cfi_register lr,r12
+	bl	V_LOCAL_FUNC(__get_datapage)
+	lwz	r5,CLOCK_REALTIME_RES(r3)
+	mtlr	r12
   	li	r3,0
   	cmpldi	cr0,r4,0
   	crclr	cr0*4+so
   	beqlr
-	lis	r5,CLOCK_REALTIME_RES@h
-	ori	r5,r5,CLOCK_REALTIME_RES@l
   	std	r3,TSPC64_TV_SEC(r4)
   	std	r5,TSPC64_TV_NSEC(r4)
   	blr