[PATCH] parisc: Avoid calling SMP cache flush functions on cache-less machines

[PATCH] parisc: Avoid calling SMP cache flush functions on cache-less machines

[Helge Deller]

At least the qemu virtual machine does not provide D- and I-caches,
so skip triggering SMP irqs to flush caches on such machines.

Signed-off-by: Helge Deller <deller@gmx.de>
---
 arch/parisc/kernel/cache.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/arch/parisc/kernel/cache.c b/arch/parisc/kernel/cache.c
index 81f36d6407f0..29839550146b 100644
--- a/arch/parisc/kernel/cache.c
+++ b/arch/parisc/kernel/cache.c
@@ -62,12 +62,14 @@ static struct pdc_btlb_info btlb_info __ro_after_init;
 void
 flush_data_cache(void)
 {
-	on_each_cpu(flush_data_cache_local, NULL, 1);
+	if (cache_info.dc_size)
+		on_each_cpu(flush_data_cache_local, NULL, 1);
 }
 void
 flush_instruction_cache(void)
 {
-	on_each_cpu(flush_instruction_cache_local, NULL, 1);
+	if (cache_info.ic_size)
+		on_each_cpu(flush_instruction_cache_local, NULL, 1);
 }
 #endif

@@ -524,7 +526,8 @@ static void cacheflush_h_tmp_function(void *dummy)

 void flush_cache_all(void)
 {
-	on_each_cpu(cacheflush_h_tmp_function, NULL, 1);
+	if (cache_info.dc_size | cache_info.ic_size)
+		on_each_cpu(cacheflush_h_tmp_function, NULL, 1);
 }

 static inline unsigned long mm_total_size(struct mm_struct *mm)
--
2.34.1

Re: [PATCH] parisc: Avoid calling SMP cache flush functions on cache-less machines

[Sven Schnelle]

Hi Helge,

Helge Deller <deller@gmx.de> writes:

> At least the qemu virtual machine does not provide D- and I-caches,
> so skip triggering SMP irqs to flush caches on such machines.
>
> Signed-off-by: Helge Deller <deller@gmx.de>

Not sure about the real performance benefit on hppa, but maybe use
static branches?