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 proposed Linux behavior for specific purpose memory is that it is reserved for direct-access (device-dax) by default and not available for any kernel usage, not even as an OOM fallback. Later, through udev scripts or another init mechanism, these device-dax claimed ranges can be reconfigured and hot-added to the available System-RAM with a unique node identifier. This device-dax management scheme implements "soft" in the "soft reserved" designation by allowing some or all of the reservation to be recovered as typical memory. This policy can be disabled at compile-time with CONFIG_EFI_SOFT_RESERVE=n, or runtime with efi=nosoftreserve. As for this patch, define the common helpers to determine if the EFI_MEMORY_SP attribute should be honored. The determination needs to be made early to prevent the kernel from being loaded into soft-reserved memory, or otherwise allowing early allocations to land there. Follow-on changes are needed per architecture to leverage these helpers in their respective mem-init paths.
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| @@ -1202,6 +1202,7 @@ extern int __init efi_setup_pcdp_console(char *); · 1201 unmodified lines | |||
| 1202 | #define EFI_DBG 8 /* Print additional debug info at runtime */ | 1202 | #define EFI_DBG 8 /* Print additional debug info at runtime */ |
| 1203 | #define EFI_NX_PE_DATA 9 /* Can runtime data regions be mapped non-executable? */ | 1203 | #define EFI_NX_PE_DATA 9 /* Can runtime data regions be mapped non-executable? */ |
| 1204 | #define EFI_MEM_ATTR 10 /* Did firmware publish an EFI_MEMORY_ATTRIBUTES table? */ | 1204 | #define EFI_MEM_ATTR 10 /* Did firmware publish an EFI_MEMORY_ATTRIBUTES table? */ |
| 1205 | #define EFI_MEM_NO_SOFT_RESERVE 11 /* Is the kernel configured to ignore soft reservations? */ | ||
| 1205 | 1206 | ||
| 1206 | #ifdef CONFIG_EFI | 1207 | #ifdef CONFIG_EFI |
| 1207 | /* | 1208 | /* |
| @@ -1212,6 +1213,14 @@ static inline bool efi_enabled(int feature) · 4 unmodified lines | |||
| 1212 | return test_bit(feature, &efi.flags) != 0; | 1213 | return test_bit(feature, &efi.flags) != 0; |
| 1213 | } | 1214 | } |
| 1214 | extern void efi_reboot(enum reboot_mode reboot_mode, const char *__unused); | 1215 | extern void efi_reboot(enum reboot_mode reboot_mode, const char *__unused); |
| 1216 | |||
| 1217 | bool __pure __efi_soft_reserve_enabled(void); | ||
| 1218 | |||
| 1219 | static inline bool __pure efi_soft_reserve_enabled(void) | ||
| 1220 | { | ||
| 1221 | return IS_ENABLED(CONFIG_EFI_SOFT_RESERVE) | ||
| 1222 | && __efi_soft_reserve_enabled(); | ||
| 1223 | } | ||
| 1215 | #else | 1224 | #else |
| 1216 | static inline bool efi_enabled(int feature) | 1225 | static inline bool efi_enabled(int feature) |
| 1217 | { | 1226 | { |
| @@ -1225,6 +1234,11 @@ efi_capsule_pending(int *reset_type) · 7 unmodified lines | |||
| 1225 | { | 1234 | { |
| 1226 | return false; | 1235 | return false; |
| 1227 | } | 1236 | } |
| 1237 | |||
| 1238 | static inline bool efi_soft_reserve_enabled(void) | ||
| 1239 | { | ||
| 1240 | return false; | ||
| 1241 | } | ||
| 1228 | #endif | 1242 | #endif |
| 1229 | 1243 | ||
| 1230 | extern int efi_status_to_err(efi_status_t status); | 1244 | extern int efi_status_to_err(efi_status_t status); |