From 1256276c98dbcfb009ac8e0687df9a1e291fd149 Mon Sep 17 00:00:00 2001 From: Konrad Rzeszutek Wilk Date: Mon, 25 Feb 2013 15:54:10 -0500 Subject: x86, doc: Fix incorrect comment about 64-bit code segment descriptors The AMD64 Architecture Programmer's Manual Volume 2, on page 89 mentions: "If the processor is running in 64-bit mode (L=1), the only valid setting of the D bit is 0." This matches with what the code does. Signed-off-by: Konrad Rzeszutek Wilk Link: http://lkml.kernel.org/r/1361825650-14031-4-git-send-email-konrad.wilk@oracle.com Signed-off-by: H. Peter Anvin --- arch/x86/kernel/head_64.S | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'arch/x86') diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S index 980053c4b9cc..37f5304e80f5 100644 --- a/arch/x86/kernel/head_64.S +++ b/arch/x86/kernel/head_64.S @@ -49,7 +49,7 @@ L3_START_KERNEL = pud_index(__START_KERNEL_map) startup_64: /* - * At this point the CPU runs in 64bit mode CS.L = 1 CS.D = 1, + * At this point the CPU runs in 64bit mode CS.L = 1 CS.D = 0, * and someone has loaded an identity mapped page table * for us. These identity mapped page tables map all of the * kernel pages and possibly all of memory. @@ -146,7 +146,7 @@ ident_complete: jmp secondary_startup_64 ENTRY(secondary_startup_64) /* - * At this point the CPU runs in 64bit mode CS.L = 1 CS.D = 1, + * At this point the CPU runs in 64bit mode CS.L = 1 CS.D = 0, * and someone has loaded a mapped page table. * * %esi holds a physical pointer to real_mode_data. -- cgit v1.2.3-55-g7522 From 058e7b5814534461b0e2468fce5a8f8d2f43c38f Mon Sep 17 00:00:00 2001 From: Matt Fleming Date: Fri, 22 Feb 2013 15:03:47 +0000 Subject: x86, efi: Mark disable_runtime as __initdata disable_runtime is only referenced from __init functions, so mark it as __initdata. Reported-by: Yinghai Lu Reviewed-by: Satoru Takeuchi Signed-off-by: Matt Fleming Link: http://lkml.kernel.org/r/1361545427-26393-1-git-send-email-matt@console-pimps.org Signed-off-by: H. Peter Anvin --- arch/x86/platform/efi/efi.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'arch/x86') diff --git a/arch/x86/platform/efi/efi.c b/arch/x86/platform/efi/efi.c index e2cd38ffc406..ec9f3254c7f1 100644 --- a/arch/x86/platform/efi/efi.c +++ b/arch/x86/platform/efi/efi.c @@ -85,7 +85,7 @@ int efi_enabled(int facility) } EXPORT_SYMBOL(efi_enabled); -static bool disable_runtime = false; +static bool __initdata disable_runtime = false; static int __init setup_noefi(char *arg) { disable_runtime = true; -- cgit v1.2.3-55-g7522 From 7c10093692ed2e6f318387d96b829320aa0ca64c Mon Sep 17 00:00:00 2001 From: H. Peter Anvin Date: Wed, 27 Feb 2013 12:46:40 -0800 Subject: x86: Make sure we can boot in the case the BDA contains pure garbage On non-BIOS platforms it is possible that the BIOS data area contains garbage instead of being zeroed or something equivalent (firmware people: we are talking of 1.5K here, so please do the sane thing.) We need on the order of 20-30K of low memory in order to boot, which may grow up to < 64K in the future. We probably want to avoid the lowest of the low memory. At the same time, it seems extremely unlikely that a legitimate EBDA would ever reach down to the 128K (which would require it to be over half a megabyte in size.) Thus, pick 128K as the cutoff for "this is insane, ignore." We may still end up reserving a bunch of extra memory on the low megabyte, but that is not really a major issue these days. In the worst case we lose 512K of RAM. This code really should be merged with trim_bios_range() in arch/x86/kernel/setup.c, but that is a bigger patch for a later merge window. Reported-by: Darren Hart Signed-off-by: H. Peter Anvin Cc: Matt Fleming Cc: Link: http://lkml.kernel.org/n/tip-oebml055yyfm8yxmria09rja@git.kernel.org --- arch/x86/kernel/head.c | 53 ++++++++++++++++++++++++++++++++------------------ 1 file changed, 34 insertions(+), 19 deletions(-) (limited to 'arch/x86') diff --git a/arch/x86/kernel/head.c b/arch/x86/kernel/head.c index 48d9d4ea1020..992f442ca155 100644 --- a/arch/x86/kernel/head.c +++ b/arch/x86/kernel/head.c @@ -5,8 +5,6 @@ #include #include -#define BIOS_LOWMEM_KILOBYTES 0x413 - /* * The BIOS places the EBDA/XBDA at the top of conventional * memory, and usually decreases the reported amount of @@ -16,17 +14,30 @@ * 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. + * + * 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. */ + +#define BIOS_LOWMEM_KILOBYTES 0x413 +#define LOWMEM_CAP 0x9f000U /* Absolute maximum */ +#define INSANE_CUTOFF 0x20000U /* Less than this = insane */ + void __init reserve_ebda_region(void) { unsigned int lowmem, ebda_addr; - /* 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. */ + /* + * 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. + */ if (paravirt_enabled()) return; @@ -37,19 +48,23 @@ void __init reserve_ebda_region(void) /* start of EBDA area */ ebda_addr = get_bios_ebda(); - /* Fixup: bios puts an EBDA in the top 64K segment */ - /* of conventional memory, but does not adjust lowmem. */ - if ((lowmem - ebda_addr) <= 0x10000) - lowmem = ebda_addr; + /* + * 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). + */ + + /* If the EBDA address is below 128K, assume it is bogus */ + if (ebda_addr < INSANE_CUTOFF) + ebda_addr = LOWMEM_CAP; - /* Fixup: bios does not report an EBDA at all. */ - /* Some old Dells seem to need 4k anyhow (bugzilla 2990) */ - if ((ebda_addr == 0) && (lowmem >= 0x9f000)) - lowmem = 0x9f000; + /* If lowmem is less than 128K, assume it is bogus */ + if (lowmem < INSANE_CUTOFF) + lowmem = LOWMEM_CAP; - /* Paranoia: should never happen, but... */ - if ((lowmem == 0) || (lowmem >= 0x100000)) - lowmem = 0x9f000; + /* Use the lower of the lowmem and EBDA markers as the cutoff */ + lowmem = min(lowmem, ebda_addr); + lowmem = min(lowmem, LOWMEM_CAP); /* Absolute cap */ /* reserve all memory between lowmem and the 1MB mark */ memblock_reserve(lowmem, 0x100000 - lowmem); -- cgit v1.2.3-55-g7522