linux-kernel - [PATCH] arm: Extend the check for RAM in /dev/mem

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Message-Id: <1562883681-18659-1-git-send-email-karahmed@amazon.de>
Date:   Fri, 12 Jul 2019 00:21:21 +0200
From:   KarimAllah Ahmed <karahmed@...zon.de>
To:     linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Cc:     KarimAllah Ahmed <karahmed@...zon.de>,
        Russell King <linux@...linux.org.uk>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Mike Rapoport <rppt@...ux.ibm.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Anders Roxell <anders.roxell@...aro.org>,
        Enrico Weigelt <info@...ux.net>,
        Thomas Gleixner <tglx@...utronix.de>,
        Mark Rutland <mark.rutland@....com>,
        James Morse <james.morse@....com>,
        Anshuman Khandual <anshuman.khandual@....com>,
        Jun Yao <yaojun8558363@...il.com>, Yu Zhao <yuzhao@...gle.com>,
        Robin Murphy <robin.murphy@....com>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>
Subject: [PATCH] arm: Extend the check for RAM in /dev/mem

Some valid RAM can live outside kernel control (e.g. using mem= kernel
command-line). For these regions, pfn_valid would return "false" causing
system RAM to be mapped as uncached. Use memblock instead to identify RAM.

Cc: Russell King <linux@...linux.org.uk>
Cc: Catalin Marinas <catalin.marinas@....com>
Cc: Will Deacon <will@...nel.org>
Cc: Mike Rapoport <rppt@...ux.ibm.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Anders Roxell <anders.roxell@...aro.org>
Cc: Enrico Weigelt <info@...ux.net>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: KarimAllah Ahmed <karahmed@...zon.de>
Cc: Mark Rutland <mark.rutland@....com>
Cc: James Morse <james.morse@....com>
Cc: Anshuman Khandual <anshuman.khandual@....com>
Cc: Jun Yao <yaojun8558363@...il.com>
Cc: Yu Zhao <yuzhao@...gle.com>
Cc: Robin Murphy <robin.murphy@....com>
Cc: Ard Biesheuvel <ard.biesheuvel@...aro.org>
Cc: linux-arm-kernel@...ts.infradead.org
Cc: linux-kernel@...r.kernel.org
Signed-off-by: KarimAllah Ahmed <karahmed@...zon.de>
---
 arch/arm/mm/mmu.c   | 2 +-
 arch/arm64/mm/mmu.c | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/arm/mm/mmu.c b/arch/arm/mm/mmu.c
index 1aa2586..492774b 100644
--- a/arch/arm/mm/mmu.c
+++ b/arch/arm/mm/mmu.c
@@ -705,7 +705,7 @@ static void __init build_mem_type_table(void)
 pgprot_t phys_mem_access_prot(struct file *file, unsigned long pfn,
 			      unsigned long size, pgprot_t vma_prot)
 {
-	if (!pfn_valid(pfn))
+	if (!memblock_is_memory(__pfn_to_phys(pfn)))
 		return pgprot_noncached(vma_prot);
 	else if (file->f_flags & O_SYNC)
 		return pgprot_writecombine(vma_prot);
diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index 3645f29..cdc3e8e 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -78,7 +78,7 @@ void set_swapper_pgd(pgd_t *pgdp, pgd_t pgd)
 pgprot_t phys_mem_access_prot(struct file *file, unsigned long pfn,
 			      unsigned long size, pgprot_t vma_prot)
 {
-	if (!pfn_valid(pfn))
+	if (!memblock_is_memory(__pfn_to_phys(pfn)))
 		return pgprot_noncached(vma_prot);
 	else if (file->f_flags & O_SYNC)
 		return pgprot_writecombine(vma_prot);
-- 
2.7.4