diff options
| -rw-r--r-- | arch/x86/include/asm/bios_ebda.h | 2 | ||||
| -rw-r--r-- | arch/x86/include/asm/x86_init.h | 4 | ||||
| -rw-r--r-- | arch/x86/kernel/ebda.c | 124 | ||||
| -rw-r--r-- | arch/x86/kernel/head32.c | 2 | ||||
| -rw-r--r-- | arch/x86/kernel/head64.c | 2 | ||||
| -rw-r--r-- | arch/x86/kernel/platform-quirks.c | 4 |
6 files changed, 88 insertions, 50 deletions
diff --git a/arch/x86/include/asm/bios_ebda.h b/arch/x86/include/asm/bios_ebda.h index 2b00c776f223..4b7b8e71607e 100644 --- a/arch/x86/include/asm/bios_ebda.h +++ b/arch/x86/include/asm/bios_ebda.h @@ -17,7 +17,7 @@ static inline unsigned int get_bios_ebda(void) return address; /* 0 means none */ } -void reserve_ebda_region(void); +void reserve_bios_regions(void); #ifdef CONFIG_X86_CHECK_BIOS_CORRUPTION /* diff --git a/arch/x86/include/asm/x86_init.h b/arch/x86/include/asm/x86_init.h index 4dcdf74dfed8..c519c052700a 100644 --- a/arch/x86/include/asm/x86_init.h +++ b/arch/x86/include/asm/x86_init.h @@ -168,14 +168,14 @@ struct x86_legacy_devices { * struct x86_legacy_features - legacy x86 features * * @rtc: this device has a CMOS real-time clock present - * @ebda_search: it's safe to search for the EBDA signature in the hardware's + * @reserve_bios_regions: it's safe to search for the EBDA signature in the hardware's * low RAM * @devices: legacy x86 devices, refer to struct x86_legacy_devices * documentation for further details. */ struct x86_legacy_features { int rtc; - int ebda_search; + int reserve_bios_regions; struct x86_legacy_devices devices; }; diff --git a/arch/x86/kernel/ebda.c b/arch/x86/kernel/ebda.c index afe65dffee80..6219eef20e2e 100644 --- a/arch/x86/kernel/ebda.c +++ b/arch/x86/kernel/ebda.c @@ -6,66 +6,104 @@ #include <asm/bios_ebda.h> /* + * This function reserves all conventional PC system BIOS related + * firmware memory areas (some of which are data, some of which + * are code), that must not be used by the kernel as available + * RAM. + * * The BIOS places the EBDA/XBDA at the top of conventional * memory, and usually decreases the reported amount of - * conventional memory (int 0x12) too. This also contains a - * workaround for Dell systems that neglect to reserve EBDA. - * The same workaround also avoids a problem with the AMD768MPX - * chipset: reserve a page before VGA to prevent PCI prefetch - * into it (errata #56). Usually the page is reserved anyways, - * unless you have no PS/2 mouse plugged in. + * conventional memory (int 0x12) too. + * + * This means that as a first approximation on most systems we can + * guess the reserved BIOS area by looking at the low BIOS RAM size + * value and assume that everything above that value (up to 1MB) is + * reserved. + * + * But life in firmware country is not that simple: + * + * - This code also contains a quirk for Dell systems that neglect + * to reserve the EBDA area in the 'RAM size' value ... + * + * - The same quirk also avoids a problem with the AMD768MPX + * chipset: reserve a page before VGA to prevent PCI prefetch + * into it (errata #56). (Usually the page is reserved anyways, + * unless you have no PS/2 mouse plugged in.) + * + * - Plus paravirt systems don't have a reliable value in the + * 'BIOS RAM size' pointer we can rely on, so we must quirk + * them too. + * + * Due to those various problems this function is deliberately + * very conservative and tries to err on the side of reserving + * too much, to not risk reserving too little. + * + * Losing a small amount of memory in the bottom megabyte is + * rarely a problem, as long as we have enough memory to install + * the SMP bootup trampoline which *must* be in this area. * - * This functions is deliberately very conservative. Losing - * memory in the bottom megabyte is rarely a problem, as long - * as we have enough memory to install the trampoline. Using - * memory that is in use by the BIOS or by some DMA device - * the BIOS didn't shut down *is* a big problem. + * Using memory that is in use by the BIOS or by some DMA device + * the BIOS didn't shut down *is* a big problem to the kernel, + * obviously. */ -#define BIOS_LOWMEM_KILOBYTES 0x413 -#define LOWMEM_CAP 0x9f000U /* Absolute maximum */ -#define INSANE_CUTOFF 0x20000U /* Less than this = insane */ +#define BIOS_RAM_SIZE_KB_PTR 0x413 -void __init reserve_ebda_region(void) +#define BIOS_START_MIN 0x20000U /* 128K, less than this is insane */ +#define BIOS_START_MAX 0x9f000U /* 640K, absolute maximum */ + +void __init reserve_bios_regions(void) { - unsigned int lowmem, ebda_addr; + unsigned int bios_start, ebda_start; /* - * To determine the position of the EBDA and the - * end of conventional memory, we need to look at - * the BIOS data area. In a paravirtual environment - * that area is absent. We'll just have to assume - * that the paravirt case can handle memory setup - * correctly, without our help. + * NOTE: In a paravirtual environment the BIOS reserved + * area is absent. We'll just have to assume that the + * paravirt case can handle memory setup correctly, + * without our help. */ - if (!x86_platform.legacy.ebda_search) + if (!x86_platform.legacy.reserve_bios_regions) return; - /* end of low (conventional) memory */ - lowmem = *(unsigned short *)__va(BIOS_LOWMEM_KILOBYTES); - lowmem <<= 10; - - /* start of EBDA area */ - ebda_addr = get_bios_ebda(); + /* Get the start address of the EBDA page: */ + ebda_start = get_bios_ebda(); /* - * Note: some old Dells seem to need 4k EBDA without - * reporting so, so just consider the memory above 0x9f000 - * to be off limits (bugzilla 2990). + * Quirk: some old Dells seem to have a 4k EBDA without + * reporting so in their BIOS RAM size value, so just + * consider the memory above 640K to be off limits + * (bugzilla 2990). + * + * We detect this case by filtering for nonsensical EBDA + * addresses below 128K, where we can assume that they + * are bogus and bump it up to a fixed 640K value: */ + if (ebda_start < BIOS_START_MIN) + ebda_start = BIOS_START_MAX; - /* If the EBDA address is below 128K, assume it is bogus */ - if (ebda_addr < INSANE_CUTOFF) - ebda_addr = LOWMEM_CAP; + /* + * BIOS RAM size is encoded in kilobytes, convert it + * to bytes to get a first guess at where the BIOS + * firmware area starts: + */ + bios_start = *(unsigned short *)__va(BIOS_RAM_SIZE_KB_PTR); + bios_start <<= 10; - /* If lowmem is less than 128K, assume it is bogus */ - if (lowmem < INSANE_CUTOFF) - lowmem = LOWMEM_CAP; + /* + * If bios_start is less than 128K, assume it is bogus + * and bump it up to 640K: + */ + if (bios_start < BIOS_START_MIN) + bios_start = BIOS_START_MAX; - /* Use the lower of the lowmem and EBDA markers as the cutoff */ - lowmem = min(lowmem, ebda_addr); - lowmem = min(lowmem, LOWMEM_CAP); /* Absolute cap */ + /* + * Use the lower of the bios_start and ebda_start + * as the starting point, but don't allow it to + * go beyond 640K: + */ + bios_start = min(bios_start, ebda_start); + bios_start = min(bios_start, BIOS_START_MAX); - /* reserve all memory between lowmem and the 1MB mark */ - memblock_reserve(lowmem, 0x100000 - lowmem); + /* Reserve all memory between bios_start and the 1MB mark: */ + memblock_reserve(bios_start, 0x100000 - bios_start); } diff --git a/arch/x86/kernel/head32.c b/arch/x86/kernel/head32.c index d784bb547a9d..2dda0bc4576e 100644 --- a/arch/x86/kernel/head32.c +++ b/arch/x86/kernel/head32.c @@ -26,7 +26,7 @@ static void __init i386_default_early_setup(void) x86_init.resources.reserve_resources = i386_reserve_resources; x86_init.mpparse.setup_ioapic_ids = setup_ioapic_ids_from_mpc; - reserve_ebda_region(); + reserve_bios_regions(); } asmlinkage __visible void __init i386_start_kernel(void) diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c index b72fb0b71dd1..99d48e7d2974 100644 --- a/arch/x86/kernel/head64.c +++ b/arch/x86/kernel/head64.c @@ -183,7 +183,7 @@ void __init x86_64_start_reservations(char *real_mode_data) copy_bootdata(__va(real_mode_data)); x86_early_init_platform_quirks(); - reserve_ebda_region(); + reserve_bios_regions(); switch (boot_params.hdr.hardware_subarch) { case X86_SUBARCH_INTEL_MID: diff --git a/arch/x86/kernel/platform-quirks.c b/arch/x86/kernel/platform-quirks.c index b2f8a33b36ff..24a50301f150 100644 --- a/arch/x86/kernel/platform-quirks.c +++ b/arch/x86/kernel/platform-quirks.c @@ -7,12 +7,12 @@ void __init x86_early_init_platform_quirks(void) { x86_platform.legacy.rtc = 1; - x86_platform.legacy.ebda_search = 0; + x86_platform.legacy.reserve_bios_regions = 0; x86_platform.legacy.devices.pnpbios = 1; switch (boot_params.hdr.hardware_subarch) { case X86_SUBARCH_PC: - x86_platform.legacy.ebda_search = 1; + x86_platform.legacy.reserve_bios_regions = 1; break; case X86_SUBARCH_XEN: case X86_SUBARCH_LGUEST: |