From: Will Deacon <will@kernel.org>
To: linux-arm-kernel@lists.infradead.org
Cc: Will Deacon <will@kernel.org>, Christoph Hellwig <hch@lst.de>,
Catalin Marinas <catalin.marinas@arm.com>,
Ard Biesheuvel <ardb@kernel.org>,
Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Subject: [PATCH 2/3] arm64: acpi: Map EFI_MEMORY_WT memory as Normal-NC
Date: Thu, 6 May 2021 10:50:33 +0100 [thread overview]
Message-ID: <20210506095034.15246-3-will@kernel.org> (raw)
In-Reply-To: <20210506095034.15246-1-will@kernel.org>
The only user we have of Normal Write-Through memory is in the ACPI code
when mapping memory regions advertised as EFI_MEMORY_WT. Since most (all?)
CPUs treat write-through as non-cacheable under the hood, don't bother
with the extra memory type here and just treat EFI_MEMORY_WT the same way
as EFI_MEMORY_WC by mapping it to the Normal-NC memory type instead.
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Will Deacon <will@kernel.org>
---
arch/arm64/kernel/acpi.c | 10 +++-------
1 file changed, 3 insertions(+), 7 deletions(-)
diff --git a/arch/arm64/kernel/acpi.c b/arch/arm64/kernel/acpi.c
index cada0b816c8a..aca5ee2a9e64 100644
--- a/arch/arm64/kernel/acpi.c
+++ b/arch/arm64/kernel/acpi.c
@@ -246,7 +246,7 @@ pgprot_t __acpi_get_mem_attribute(phys_addr_t addr)
* types" of UEFI 2.5 section 2.3.6.1, each EFI memory type is
* mapped to a corresponding MAIR attribute encoding.
* The EFI memory attribute advises all possible capabilities
- * of a memory region. We use the most efficient capability.
+ * of a memory region.
*/
u64 attr;
@@ -254,9 +254,7 @@ pgprot_t __acpi_get_mem_attribute(phys_addr_t addr)
attr = efi_mem_attributes(addr);
if (attr & EFI_MEMORY_WB)
return PAGE_KERNEL;
- if (attr & EFI_MEMORY_WT)
- return __pgprot(PROT_NORMAL_WT);
- if (attr & EFI_MEMORY_WC)
+ if (attr & (EFI_MEMORY_WC | EFI_MEMORY_WT))
return __pgprot(PROT_NORMAL_NC);
return __pgprot(PROT_DEVICE_nGnRnE);
}
@@ -340,9 +338,7 @@ void __iomem *acpi_os_ioremap(acpi_physical_address phys, acpi_size size)
default:
if (region->attribute & EFI_MEMORY_WB)
prot = PAGE_KERNEL;
- else if (region->attribute & EFI_MEMORY_WT)
- prot = __pgprot(PROT_NORMAL_WT);
- else if (region->attribute & EFI_MEMORY_WC)
+ else if (region->attribute & (EFI_MEMORY_WC | EFI_MEMORY_WT))
prot = __pgprot(PROT_NORMAL_NC);
}
}
--
2.31.1.607.g51e8a6a459-goog
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next prev parent reply other threads:[~2021-05-06 9:53 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-06 9:50 [PATCH 0/3] Free up a couple of MAIRs Will Deacon
2021-05-06 9:50 ` [PATCH 1/3] arm64: mm: Remove unused support for Device-GRE memory type Will Deacon
2021-05-06 13:25 ` Catalin Marinas
2021-05-06 9:50 ` Will Deacon [this message]
2021-05-06 10:14 ` [PATCH 2/3] arm64: acpi: Map EFI_MEMORY_WT memory as Normal-NC Ard Biesheuvel
2021-05-06 13:25 ` Catalin Marinas
2021-05-06 17:45 ` Ard Biesheuvel
2021-05-06 10:20 ` Mark Rutland
2021-05-06 10:46 ` Will Deacon
2021-05-06 11:00 ` Mark Rutland
2021-05-06 11:30 ` Ard Biesheuvel
2021-05-06 9:50 ` [PATCH 3/3] arm64: mm: Remove unused support for Normal-WT memory type Will Deacon
2021-05-06 13:26 ` Catalin Marinas
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