Re: [PATCH] x86 ACPI: normalize segment descriptor register on resume

[Len Brown <lenb@kernel.org>]

Applied.

thanks,
-Len

On Tue, 24 Jun 2008, Rafael J. Wysocki wrote:

> 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	$16, %cx
> +	lgdtl	%cs:wakeup_gdt
> +	movl	%cr0, %eax
> +	orb	$X86_CR0_PE, %al
> +	movl	%eax, %cr0
> +	jmp	1f
> +1:	ljmpw	$8, $2f
> +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();
>