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SubjectRe: [PATCH v1 2/2] acpi, x86: Remove encryption mask from ACPI page protection type
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On 7/27/2017 9:41 AM, Borislav Petkov wrote:
> On Wed, Jul 26, 2017 at 01:04:34PM -0500, Tom Lendacky wrote:
>> The function arch_apei_get_mem_attributes() is used to set the page
>> protection type for ACPI physical addresses. When SME is active, the
>> associated protection type needs to not have the encryption mask set
>> since the ACPI tables live in un-encrypted memory. Modify the
>> arch_apei_get_mem_attributes() function to remove the encryption mask
>> when SME is active by returning the PAGE_KERNEL_IO protection type.
>>
>> Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
>> ---
>> arch/x86/include/asm/acpi.h | 7 ++++++-
>> 1 file changed, 6 insertions(+), 1 deletion(-)
>>
>> diff --git a/arch/x86/include/asm/acpi.h b/arch/x86/include/asm/acpi.h
>> index 562286f..89df39d 100644
>> --- a/arch/x86/include/asm/acpi.h
>> +++ b/arch/x86/include/asm/acpi.h
>> @@ -34,6 +34,7 @@
>>
>> #ifdef CONFIG_ACPI_APEI
>> # include <asm/pgtable_types.h>
>> +# include <linux/mem_encrypt.h>
>> #endif
>>
>> #ifdef CONFIG_ACPI
>> @@ -164,8 +165,12 @@ static inline pgprot_t arch_apei_get_mem_attribute(phys_addr_t addr)
>> * anything other than PAGE_KERNEL (some arm64 platforms
>> * require the equivalent of PAGE_KERNEL_NOCACHE), return that
>> * until we know differently.
>> + *
>> + * When SME is active, the ACPI information will not reside in
>> + * in memory in an encrypted state so return a protection attribute
>> + * that does not have the encryption bit set.
>> */
>> - return PAGE_KERNEL;
>> + return sme_active() ? PAGE_KERNEL_IO : PAGE_KERNEL;
>
> Why isn't there a PAGE_KERNEL_NOENC define which you can simply return
> instead of testing?

Sounds like something I should add to pgtable_types.h (which has a
#define for PAGE_KERNEL_EXEC_NOENC, but not PAGE_KERNEL_NOENC). I'll
create that #define.

As for the sme_active() check I was getting ahead of myself since
under SEV the encryption mask is needed. I'll change it to just
return PAGE_KERNEL_NOENC and then worry about the SEV change in
the SEV patches.

Thanks,
Tom

>

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