linux-kernel - [PATCH 1/6] powerpc/mm/32: Use pfn_valid to check if pointer is in RAM

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Date:   Tue, 20 Feb 2018 17:14:19 +0100
From:   Jonathan Neuschäfer <j.neuschaefer@....net>
To:     linuxppc-dev@...ts.ozlabs.org
Cc:     linux-kernel@...r.kernel.org,
        Michael Ellerman <mpe@...erman.id.au>, linux-mm@...ck.org,
        Joel Stanley <joel@....id.au>,
        Jonathan Neuschäfer <j.neuschaefer@....net>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Christophe Leroy <christophe.leroy@....fr>,
        Balbir Singh <bsingharora@...il.com>,
        Guenter Roeck <linux@...ck-us.net>
Subject: [PATCH 1/6] powerpc/mm/32: Use pfn_valid to check if pointer is in RAM

The Nintendo Wii has a memory layout that places two chunks of RAM at
non-adjacent addresses, and MMIO between them. Currently, the allocation
of these MMIO areas is made possible by declaring the MMIO hole as
reserved memory and allowing reserved memory to be allocated (cf.
wii_memory_fixups).

This patch is the first step towards proper support for discontiguous
memory on PPC32 by using pfn_valid to check if a pointer points into
RAM, rather than open-coding the check. It should result in no
functional difference.

Signed-off-by: Jonathan Neuschäfer <j.neuschaefer@....net>
---
 arch/powerpc/mm/pgtable_32.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/powerpc/mm/pgtable_32.c b/arch/powerpc/mm/pgtable_32.c
index d35d9ad3c1cd..b5c009893a44 100644
--- a/arch/powerpc/mm/pgtable_32.c
+++ b/arch/powerpc/mm/pgtable_32.c
@@ -147,7 +147,7 @@ __ioremap_caller(phys_addr_t addr, unsigned long size, unsigned long flags,
 	 * Don't allow anybody to remap normal RAM that we're using.
 	 * mem_init() sets high_memory so only do the check after that.
 	 */
-	if (slab_is_available() && (p < virt_to_phys(high_memory)) &&
+	if (slab_is_available() && pfn_valid(__phys_to_pfn(p)) &&
 	    !(__allow_ioremap_reserved && memblock_is_region_reserved(p, size))) {
 		printk("__ioremap(): phys addr 0x%llx is RAM lr %ps\n",
 		       (unsigned long long)p, __builtin_return_address(0));
-- 
2.16.1