On 11 August 2015 at 23:57, Matt Fleming <m...@codeblueprint.co.uk> wrote:
> On Sat, 08 Aug, at 10:18:52AM, Jonathan (Zhixiong) Zhang wrote:
>> From: "Jonathan (Zhixiong) Zhang" <zjzh...@codeaurora.org>
>>
>> Table 8 of UEFI 2.5 section 2.3.6.1 defines mappings from EFI
>> memory types to MAIR attribute encodings for arm64.
>>
>> If the physical address has memory attributes defined by EFI
>> memmap as EFI_MEMORY_[UC|WC|WT], return approprate page protection
>> type according to the UEFI spec. Otherwise, return PAGE_KERNEL.
>>
>> Reviewed-by: Catalin Marinas <catalin.mari...@arm.com>
>> Acked-by: Hanjun Guo <hanjun....@linaro.org>
>> Signed-off-by: Jonathan (Zhixiong) Zhang <zjzh...@codeaurora.org>
>> ---
>> arch/arm64/include/asm/acpi.h | 30 ++++++++++++++++++++++++++++++
>> 1 file changed, 30 insertions(+)
>>
>> diff --git a/arch/arm64/include/asm/acpi.h b/arch/arm64/include/asm/acpi.h
>> index 614096732839..b77a2d133da9 100644
>> --- a/arch/arm64/include/asm/acpi.h
>> +++ b/arch/arm64/include/asm/acpi.h
>> @@ -19,6 +19,11 @@
>> #include <asm/psci.h>
>> #include <asm/smp_plat.h>
>>
>> +#ifdef CONFIG_ACPI_APEI
>> +#include <linux/efi.h>
>> +#include <asm/pgtable.h>
>> +#endif
>> +
>> /* Macros for consistency checks of the GICC subtable of MADT */
>> #define ACPI_MADT_GICC_LENGTH \
>> (acpi_gbl_FADT.header.revision < 6 ? 76 : 80)
>> @@ -91,4 +95,29 @@ static inline const char *acpi_get_enable_method(int cpu)
>> {
>> return acpi_psci_present() ? "psci" : NULL;
>> }
>> +
>> +#ifdef CONFIG_ACPI_APEI
>> +static inline pgprot_t arch_apei_get_mem_attribute(phys_addr_t addr)
>> +{
>> + /*
>> + * According to "Table 8 Map: EFI memory types to AArch64 memory types"
>> + * of UEFI 2.5 section 2.3.6.1, each EFI memory type is mapped to
>> + * corresponding MAIR attribute encoding.
>> + * The EFI memory attribute advises all possible capabilities of a
>> + * memory region. We use the most efficient capability.
>> + */
>> +
>> + u64 attr;
>> +
>> + 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)
>> + return __pgprot(PROT_NORMAL_NC);
>> + return __pgprot(PROT_DEVICE_nGnRnE);
>> +}
>> +#endif
>> +
>> #endif /*_ASM_ACPI_H*/
>
> Everyone happy with this change? Ard?
>
Yes, this looks fine. As long as any region that has the EFI_MEMORY_WB
attribute gets mapped as PAGE_KERNEL, we know we won't be violating
any architectural mismatched attributes constraints (since all
EFI_MEMORY_WB regions, even the occupied ones, are covered by the
kernel direct mapping as well)
For the other ones, it is merely an optimization, but arguably still
an improvement.
Reviewed-by: Ard Biesheuvel <ard.biesheu...@linaro.org>
Thanks,
Ard.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
