linux-kernel - [PATCH v2 6/9] powerpc/mem: flush_dcache_icache

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Message-Id: <79ed5d7914f497cd5fcd681ca2f4d50a91719455.1617895813.git.christophe.leroy@csgroup.eu>
Date:   Thu,  8 Apr 2021 15:30:30 +0000 (UTC)
From:   Christophe Leroy <christophe.leroy@...roup.eu>
To:     Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>
Cc:     linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: [PATCH v2 6/9] powerpc/mem: flush_dcache_icache_phys() is for HIGHMEM
 pages only

__flush_dcache_icache() is usable for non HIGHMEM pages on
every platform.

It is only for HIGHMEM pages that BOOKE needs kmap() and
BOOK3S needs flush_dcache_icache_phys().

So make flush_dcache_icache_phys() dependent on CONFIG_HIGHMEM and
call it only when it is a HIGHMEM page.

We could make flush_dcache_icache_phys() available at all time,
but as it is declared NOKPROBE_SYMBOL(), GCC doesn't optimise
it out when it is not used.

So define a stub for !CONFIG_HIGHMEM in order to remove the #ifdef in
flush_dcache_icache_page() and use IS_ENABLED() instead.

Signed-off-by: Christophe Leroy <christophe.leroy@...roup.eu>
---
 arch/powerpc/mm/cacheflush.c | 17 +++++++++--------
 1 file changed, 9 insertions(+), 8 deletions(-)

diff --git a/arch/powerpc/mm/cacheflush.c b/arch/powerpc/mm/cacheflush.c
index 3268a3e55c3f..2d92cb6bc423 100644
--- a/arch/powerpc/mm/cacheflush.c
+++ b/arch/powerpc/mm/cacheflush.c
@@ -76,7 +76,7 @@ void flush_icache_range(unsigned long start, unsigned long stop)
 }
 EXPORT_SYMBOL(flush_icache_range);
 
-#if !defined(CONFIG_PPC_8xx) && !defined(CONFIG_PPC64)
+#ifdef CONFIG_HIGHMEM
 /**
  * flush_dcache_icache_phys() - Flush a page by it's physical address
  * @physaddr: the physical address of the page
@@ -115,7 +115,11 @@ static void flush_dcache_icache_phys(unsigned long physaddr)
 		: "ctr", "memory");
 }
 NOKPROBE_SYMBOL(flush_dcache_icache_phys)
-#endif // !defined(CONFIG_PPC_8xx) && !defined(CONFIG_PPC64)
+#else
+static void flush_dcache_icache_phys(unsigned long physaddr)
+{
+}
+#endif
 
 /*
  * This is called when a page has been modified by the kernel.
@@ -185,18 +189,15 @@ void flush_dcache_icache_page(struct page *page)
 	if (PageCompound(page))
 		return flush_dcache_icache_hugepage(page);
 
-#if defined(CONFIG_PPC_8xx) || defined(CONFIG_PPC64)
-	/* On 8xx there is no need to kmap since highmem is not supported */
-	__flush_dcache_icache(page_address(page));
-#else
-	if (IS_ENABLED(CONFIG_BOOKE) || sizeof(phys_addr_t) > sizeof(void *)) {
+	if (!PageHighMem(page)) {
+		__flush_dcache_icache(lowmem_page_address(page));
+	} else if (IS_ENABLED(CONFIG_BOOKE) || sizeof(phys_addr_t) > sizeof(void *)) {
 		void *start = kmap_atomic(page);
 		__flush_dcache_icache(start);
 		kunmap_atomic(start);
 	} else {
 		flush_dcache_icache_phys(page_to_phys(page));
 	}
-#endif
 }
 EXPORT_SYMBOL(flush_dcache_icache_page);
 
-- 
2.25.0