| Message ID | 155925717803.3775979.14412010256191901040.stgit@dwillia2-desk3.amr.corp.intel.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | EFI Specific Purpose Memory Support | expand |
On Fri, 31 May 2019 at 01:13, Dan Williams <dan.j.williams@intel.com> wrote: > > UEFI 2.8 defines an EFI_MEMORY_SP attribute bit to augment the > interpretation of the EFI Memory Types as "reserved for a specific > purpose". The intent of this bit is to allow the OS to identify precious > or scarce memory resources and optionally manage it separately from > EfiConventionalMemory. As defined older OSes that do not know about this > attribute are permitted to ignore it and the memory will be handled > according to the OS default policy for the given memory type. > > In other words, this "specific purpose" hint is deliberately weaker than > EfiReservedMemoryType in that the system continues to operate if the OS > takes no action on the attribute. The risk of taking no action is > potentially unwanted / unmovable kernel allocations from the designated > resource that prevent the full realization of the "specific purpose". > For example, consider a system with a high-bandwidth memory pool. Older > kernels are permitted to boot and consume that memory as conventional > "System-RAM" newer kernels may arrange for that memory to be set aside > by the system administrator for a dedicated high-bandwidth memory aware > application to consume. > > Specifically, this mechanism allows for the elimination of scenarios > where platform firmware tries to game OS policy by lying about ACPI SLIT > values, i.e. claiming that a precious memory resource has a high > distance to trigger the OS to avoid it by default. > > Implement simple detection of the bit for EFI memory table dumps and > save the kernel policy for a follow-on change. > > Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org> > Signed-off-by: Dan Williams <dan.j.williams@intel.com> Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> > --- > drivers/firmware/efi/efi.c | 5 +++-- > include/linux/efi.h | 1 + > 2 files changed, 4 insertions(+), 2 deletions(-) > > diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c > index 55b77c576c42..81db09485881 100644 > --- a/drivers/firmware/efi/efi.c > +++ b/drivers/firmware/efi/efi.c > @@ -848,15 +848,16 @@ char * __init efi_md_typeattr_format(char *buf, size_t size, > if (attr & ~(EFI_MEMORY_UC | EFI_MEMORY_WC | EFI_MEMORY_WT | > EFI_MEMORY_WB | EFI_MEMORY_UCE | EFI_MEMORY_RO | > EFI_MEMORY_WP | EFI_MEMORY_RP | EFI_MEMORY_XP | > - EFI_MEMORY_NV | > + EFI_MEMORY_NV | EFI_MEMORY_SP | > EFI_MEMORY_RUNTIME | EFI_MEMORY_MORE_RELIABLE)) > snprintf(pos, size, "|attr=0x%016llx]", > (unsigned long long)attr); > else > snprintf(pos, size, > - "|%3s|%2s|%2s|%2s|%2s|%2s|%2s|%3s|%2s|%2s|%2s|%2s]", > + "|%3s|%2s|%2s|%2s|%2s|%2s|%2s|%2s|%3s|%2s|%2s|%2s|%2s]", > attr & EFI_MEMORY_RUNTIME ? "RUN" : "", > attr & EFI_MEMORY_MORE_RELIABLE ? "MR" : "", > + attr & EFI_MEMORY_SP ? "SP" : "", > attr & EFI_MEMORY_NV ? "NV" : "", > attr & EFI_MEMORY_XP ? "XP" : "", > attr & EFI_MEMORY_RP ? "RP" : "", > diff --git a/include/linux/efi.h b/include/linux/efi.h > index 6ebc2098cfe1..91368f5ce114 100644 > --- a/include/linux/efi.h > +++ b/include/linux/efi.h > @@ -112,6 +112,7 @@ typedef struct { > #define EFI_MEMORY_MORE_RELIABLE \ > ((u64)0x0000000000010000ULL) /* higher reliability */ > #define EFI_MEMORY_RO ((u64)0x0000000000020000ULL) /* read-only */ > +#define EFI_MEMORY_SP ((u64)0x0000000000040000ULL) /* special purpose */ > #define EFI_MEMORY_RUNTIME ((u64)0x8000000000000000ULL) /* range requires runtime mapping */ > #define EFI_MEMORY_DESCRIPTOR_VERSION 1 > >
diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c index 55b77c576c42..81db09485881 100644 --- a/drivers/firmware/efi/efi.c +++ b/drivers/firmware/efi/efi.c @@ -848,15 +848,16 @@ char * __init efi_md_typeattr_format(char *buf, size_t size, if (attr & ~(EFI_MEMORY_UC | EFI_MEMORY_WC | EFI_MEMORY_WT | EFI_MEMORY_WB | EFI_MEMORY_UCE | EFI_MEMORY_RO | EFI_MEMORY_WP | EFI_MEMORY_RP | EFI_MEMORY_XP | - EFI_MEMORY_NV | + EFI_MEMORY_NV | EFI_MEMORY_SP | EFI_MEMORY_RUNTIME | EFI_MEMORY_MORE_RELIABLE)) snprintf(pos, size, "|attr=0x%016llx]", (unsigned long long)attr); else snprintf(pos, size, - "|%3s|%2s|%2s|%2s|%2s|%2s|%2s|%3s|%2s|%2s|%2s|%2s]", + "|%3s|%2s|%2s|%2s|%2s|%2s|%2s|%2s|%3s|%2s|%2s|%2s|%2s]", attr & EFI_MEMORY_RUNTIME ? "RUN" : "", attr & EFI_MEMORY_MORE_RELIABLE ? "MR" : "", + attr & EFI_MEMORY_SP ? "SP" : "", attr & EFI_MEMORY_NV ? "NV" : "", attr & EFI_MEMORY_XP ? "XP" : "", attr & EFI_MEMORY_RP ? "RP" : "", diff --git a/include/linux/efi.h b/include/linux/efi.h index 6ebc2098cfe1..91368f5ce114 100644 --- a/include/linux/efi.h +++ b/include/linux/efi.h @@ -112,6 +112,7 @@ typedef struct { #define EFI_MEMORY_MORE_RELIABLE \ ((u64)0x0000000000010000ULL) /* higher reliability */ #define EFI_MEMORY_RO ((u64)0x0000000000020000ULL) /* read-only */ +#define EFI_MEMORY_SP ((u64)0x0000000000040000ULL) /* special purpose */ #define EFI_MEMORY_RUNTIME ((u64)0x8000000000000000ULL) /* range requires runtime mapping */ #define EFI_MEMORY_DESCRIPTOR_VERSION 1
UEFI 2.8 defines an EFI_MEMORY_SP attribute bit to augment the interpretation of the EFI Memory Types as "reserved for a specific purpose". The intent of this bit is to allow the OS to identify precious or scarce memory resources and optionally manage it separately from EfiConventionalMemory. As defined older OSes that do not know about this attribute are permitted to ignore it and the memory will be handled according to the OS default policy for the given memory type. In other words, this "specific purpose" hint is deliberately weaker than EfiReservedMemoryType in that the system continues to operate if the OS takes no action on the attribute. The risk of taking no action is potentially unwanted / unmovable kernel allocations from the designated resource that prevent the full realization of the "specific purpose". For example, consider a system with a high-bandwidth memory pool. Older kernels are permitted to boot and consume that memory as conventional "System-RAM" newer kernels may arrange for that memory to be set aside by the system administrator for a dedicated high-bandwidth memory aware application to consume. Specifically, this mechanism allows for the elimination of scenarios where platform firmware tries to game OS policy by lying about ACPI SLIT values, i.e. claiming that a precious memory resource has a high distance to trigger the OS to avoid it by default. Implement simple detection of the bit for EFI memory table dumps and save the kernel policy for a follow-on change. Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org> Signed-off-by: Dan Williams <dan.j.williams@intel.com> --- drivers/firmware/efi/efi.c | 5 +++-- include/linux/efi.h | 1 + 2 files changed, 4 insertions(+), 2 deletions(-)