> Hi,
>
> The patch below fixes the regression described at
>
http://bugzilla.kernel.org/show_bug.cgi?id=10927
> which is caused by the fact that some BIOSes call the kernel's resume code with
> post-protected mode garbage in segment registers.
>
> Apart from Dell laptops referred to in the chagelog it has a potential to fix
> some other systems on which resume from suspend to RAM fails in a mysterious
> way and the probability of it breaking things is rather small, so IMO it would
> be nice to have in 2.6.26.
>
> Thanks,
> Rafael
>
>
> ---
> From: H. Peter Anvin <hpa@zytor.com>
>
> x86 ACPI: normalize segment descriptor register on resume
>
> Some Dell laptops enter resume with apparent garbage in the segment
> descriptor registers (almost certainly the result of a botched
> transition from protected to real mode.) The only way to clean that
> up is to enter protected mode ourselves and clean out the descriptor
> registers.
>
> This fixes resume on Dell XPS M1210 and Dell D620.
>
> Reference:
http://bugzilla.kernel.org/show_bug.cgi?id=10927
>
> Signed-off-by: H. Peter Anvin <hpa@zytor.com>
> Tested-by: Kirill A. Shutemov <kirill@shutemov.name>
> Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
> ---
> arch/x86/kernel/acpi/realmode/wakeup.S | 38 ++++++++++++++++++++++++++++++++-
> arch/x86/kernel/acpi/realmode/wakeup.h | 5 ++++
> arch/x86/kernel/acpi/sleep.c | 16 +++++++++++++
> drivers/acpi/sleep/main.c | 5 +---
> 4 files changed, 59 insertions(+), 5 deletions(-)
>
> Index: linux-2.6/arch/x86/kernel/acpi/realmode/wakeup.S
> ===================================================================
> --- linux-2.6.orig/arch/x86/kernel/acpi/realmode/wakeup.S
> +++ linux-2.6/arch/x86/kernel/acpi/realmode/wakeup.S
> @@ -5,6 +5,7 @@
> #include <asm/msr-index.h>
> #include <asm/page.h>
> #include <asm/pgtable.h>
> +#include <asm/processor-flags.h>
>
> .code16
> .section ".header", "a"
> @@ -24,6 +25,11 @@ pmode_gdt: .quad 0
> realmode_flags: .long 0
> real_magic: .long 0
> trampoline_segment: .word 0
> +_pad1: .byte 0
> +wakeup_jmp: .byte 0xea /* ljmpw */
> +wakeup_jmp_off: .word 3f
> +wakeup_jmp_seg: .word 0
> +wakeup_gdt: .quad 0, 0, 0
> signature: .long 0x51ee1111
>
> .text
> @@ -34,11 +40,34 @@ _start:
> cli
> cld
>
> + /* Apparently some dimwit BIOS programmers don't know how to
> + program a PM to RM transition, and we might end up here with
> + junk in the data segment descriptor registers. The only way
> + to repair that is to go into PM and fix it ourselves... */
> + movw , %cx
> + lgdtl %cs:wakeup_gdt
> + movl %cr0, %eax
> + orb $X86_CR0_PE, %al
> + movl %eax, %cr0
> + jmp 1f
> +1: ljmpw , f
> +2:
> + movw %cx, %ds
> + movw %cx, %es
> + movw %cx, %ss
> + movw %cx, %fs
> + movw %cx, %gs
> +
> + andb $~X86_CR0_PE, %al
> + movl %eax, %cr0
> + jmp wakeup_jmp
> +3:
> /* Set up segments */
> movw %cs, %ax
> movw %ax, %ds
> movw %ax, %es
> movw %ax, %ss
> + lidtl wakeup_idt
>
> movl $wakeup_stack_end, %esp
>
> @@ -98,7 +127,14 @@ bogus_real_magic:
> jmp 1b
>
> .data
> - .balign 4
> + .balign 8
> +
> + /* This is the standard real-mode IDT */
> +wakeup_idt:
> + .word 0xffff /* limit */
> + .long 0 /* address */
> + .word 0
> +
> .globl HEAP, heap_end
> HEAP:
> .long wakeup_heap
> Index: linux-2.6/arch/x86/kernel/acpi/realmode/wakeup.h
> ===================================================================
> --- linux-2.6.orig/arch/x86/kernel/acpi/realmode/wakeup.h
> +++ linux-2.6/arch/x86/kernel/acpi/realmode/wakeup.h
> @@ -24,6 +24,11 @@ struct wakeup_header {
> u32 realmode_flags;
> u32 real_magic;
> u16 trampoline_segment; /* segment with trampoline code, 64-bit only */
> + u8 _pad1;
> + u8 wakeup_jmp;
> + u16 wakeup_jmp_off;
> + u16 wakeup_jmp_seg;
> + u64 wakeup_gdt[3];
> u32 signature; /* To check we have correct structure */
> } __attribute__((__packed__));
>
> Index: linux-2.6/arch/x86/kernel/acpi/sleep.c
> ===================================================================
> --- linux-2.6.orig/arch/x86/kernel/acpi/sleep.c
> +++ linux-2.6/arch/x86/kernel/acpi/sleep.c
> @@ -50,6 +50,20 @@ int acpi_save_state_mem(void)
>
> header->video_mode = saved_video_mode;
>
> + header->wakeup_jmp_seg = acpi_wakeup_address >> 4;
> + /* GDT[0]: GDT self-pointer */
> + header->wakeup_gdt[0] =
> + (u64)(sizeof(header->wakeup_gdt) - 1) +
> + ((u64)(acpi_wakeup_address +
> + ((char *)&header->wakeup_gdt - (char *)acpi_realmode))
> + << 16);
> + /* GDT[1]: real-mode-like code segment */
> + header->wakeup_gdt[1] = (0x009bULL << 40) +
> + ((u64)acpi_wakeup_address << 16) + 0xffff;
> + /* GDT[2]: real-mode-like data segment */
> + header->wakeup_gdt[2] = (0x0093ULL << 40) +
> + ((u64)acpi_wakeup_address << 16) + 0xffff;
> +
> #ifndef CONFIG_64BIT
> store_gdt((struct desc_ptr *)&header->pmode_gdt);
>
> @@ -111,7 +125,7 @@ void __init acpi_reserve_bootmem(void)
> return;
> }
>
> - acpi_wakeup_address = acpi_realmode;
> + acpi_wakeup_address = virt_to_phys((void *)acpi_realmode);
> }
>
>
> Index: linux-2.6/drivers/acpi/sleep/main.c
> ===================================================================
> --- linux-2.6.orig/drivers/acpi/sleep/main.c
> +++ linux-2.6/drivers/acpi/sleep/main.c
> @@ -32,9 +32,8 @@ static int acpi_sleep_prepare(u32 acpi_s
> if (!acpi_wakeup_address) {
> return -EFAULT;
> }
> - acpi_set_firmware_waking_vector((acpi_physical_address)
> - virt_to_phys((void *)
> - acpi_wakeup_address));
> + acpi_set_firmware_waking_vector(
> + (acpi_physical_address)acpi_wakeup_address);
>
> }
> ACPI_FLUSH_CPU_CACHE();
>
