Re: [PATCH] x86, x86-64, gdt, hibernate: Store/load GDT for hibernate path.

["Rafael J. Wysocki" <rjw@sisk.pl>]

On Wednesday, May 01, 2013 09:53:30 PM Konrad Rzeszutek Wilk wrote:
> The git commite7a5cd063c7b4c58417f674821d63f5eb6747e37
> ("x86-64, gdt: Store/load GDT for ACPI S3 or hibernate/resume path
> is not needed.") assumes that for the hibernate path the booting
> kernel and the resuming kernel MUST be the same. That is certainly
> the case for a 32-bit kernel (see check_image_kernel and
> CONFIG_ARCH_HIBERNATION_HEADER config option).
> 
> However for 64-bit kernels it is OK to have a different kernel
> version (and size of the image) of the booting and resuming kernels.
> Hence the above mentioned git commit introduces an regression.
> 
> This patch fixes it by introducing a 'struct desc_ptr gdt_desc'
> back in the 'struct saved_context'. However instead of having in the
> 'save_processor_state' and 'restore_processor_state' the
> store/load_gdt calls, we are only saving the GDT in the
> save_processor_state.
> 
> For the restore path the lgdt operation is done in
> hibernate_asm_[32|64].S in the 'restore_registers' path.
> 
> The apt reader of this description will recognize that only 64-bit
> kernels need this treatment, not 32-bit. This patch adds the logic
> in the 32-bit path to be more similar to 64-bit so that in the future
> the unification process can take advantage of this.
> 
> Suggested-by: "H. Peter Anvin" <hpa@zytor.com>
> CC: "Rafael J. Wysocki" <rjw@sisk.pl>
> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

> ---
>  arch/x86/include/asm/suspend_32.h |  1 +
>  arch/x86/include/asm/suspend_64.h |  2 ++
>  arch/x86/kernel/asm-offsets_32.c  |  3 +++
>  arch/x86/kernel/asm-offsets_64.c  |  1 +
>  arch/x86/power/cpu.c              | 15 ++++++++++-----
>  arch/x86/power/hibernate_asm_32.S |  4 ++++
>  arch/x86/power/hibernate_asm_64.S |  3 +++
>  7 files changed, 24 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/x86/include/asm/suspend_32.h b/arch/x86/include/asm/suspend_32.h
> index f6064b7..552d6c9 100644
> --- a/arch/x86/include/asm/suspend_32.h
> +++ b/arch/x86/include/asm/suspend_32.h
> @@ -15,6 +15,7 @@ struct saved_context {
>  	unsigned long cr0, cr2, cr3, cr4;
>  	u64 misc_enable;
>  	bool misc_enable_saved;
> +	struct desc_ptr gdt_desc;
>  	struct desc_ptr idt;
>  	u16 ldt;
>  	u16 tss;
> diff --git a/arch/x86/include/asm/suspend_64.h b/arch/x86/include/asm/suspend_64.h
> index 97b84e0..bc62328 100644
> --- a/arch/x86/include/asm/suspend_64.h
> +++ b/arch/x86/include/asm/suspend_64.h
> @@ -25,6 +25,8 @@ struct saved_context {
>  	u64 misc_enable;
>  	bool misc_enable_saved;
>  	unsigned long efer;
> +	u16 gdt_pad; /* Unused */
> +	struct desc_ptr gdt_desc;
>  	u16 idt_pad;
>  	u16 idt_limit;
>  	unsigned long idt_base;
> diff --git a/arch/x86/kernel/asm-offsets_32.c b/arch/x86/kernel/asm-offsets_32.c
> index 85d98ab..0ef4bba 100644
> --- a/arch/x86/kernel/asm-offsets_32.c
> +++ b/arch/x86/kernel/asm-offsets_32.c
> @@ -60,6 +60,9 @@ void foo(void)
>  	OFFSET(IA32_RT_SIGFRAME_sigcontext, rt_sigframe, uc.uc_mcontext);
>  	BLANK();
>  
> +	OFFSET(saved_context_gdt_desc, saved_context, gdt_desc);
> +	BLANK();
> +
>  	/* Offset from the sysenter stack to tss.sp0 */
>  	DEFINE(TSS_sysenter_sp0, offsetof(struct tss_struct, x86_tss.sp0) -
>  		 sizeof(struct tss_struct));
> diff --git a/arch/x86/kernel/asm-offsets_64.c b/arch/x86/kernel/asm-offsets_64.c
> index 1b4754f..e7c798b 100644
> --- a/arch/x86/kernel/asm-offsets_64.c
> +++ b/arch/x86/kernel/asm-offsets_64.c
> @@ -73,6 +73,7 @@ int main(void)
>  	ENTRY(cr3);
>  	ENTRY(cr4);
>  	ENTRY(cr8);
> +	ENTRY(gdt_desc);
>  	BLANK();
>  #undef ENTRY
>  
> diff --git a/arch/x86/power/cpu.c b/arch/x86/power/cpu.c
> index 6d6e907..1cf5b30 100644
> --- a/arch/x86/power/cpu.c
> +++ b/arch/x86/power/cpu.c
> @@ -25,16 +25,12 @@
>  #include <asm/cpu.h>
>  
>  #ifdef CONFIG_X86_32
> -static struct saved_context saved_context;
> -
>  unsigned long saved_context_ebx;
>  unsigned long saved_context_esp, saved_context_ebp;
>  unsigned long saved_context_esi, saved_context_edi;
>  unsigned long saved_context_eflags;
> -#else
> -/* CONFIG_X86_64 */
> -struct saved_context saved_context;
>  #endif
> +struct saved_context saved_context;
>  
>  /**
>   *	__save_processor_state - save CPU registers before creating a
> @@ -67,6 +63,15 @@ static void __save_processor_state(struct saved_context *ctxt)
>  /* CONFIG_X86_64 */
>  	store_idt((struct desc_ptr *)&ctxt->idt_limit);
>  #endif
> +	/*
> +	 * We save it here, but restore it only in the hibernate case.
> +	 * For ACPI S3 resume, this is loaded via 'early_gdt_desc' in 64-bit
> +	 * mode in "secondary_startup_64". In 32-bit mode it is done via
> +	 * 'pmode_gdt' in wakeup_start.
> +	 */
> +	ctxt->gdt_desc.size = GDT_SIZE - 1;
> +	ctxt->gdt_desc.address = (unsigned long)get_cpu_gdt_table(smp_processor_id());
> +
>  	store_tr(ctxt->tr);
>  
>  	/* XMM0..XMM15 should be handled by kernel_fpu_begin(). */
> diff --git a/arch/x86/power/hibernate_asm_32.S b/arch/x86/power/hibernate_asm_32.S
> index ad47dae..1d0fa0e 100644
> --- a/arch/x86/power/hibernate_asm_32.S
> +++ b/arch/x86/power/hibernate_asm_32.S
> @@ -75,6 +75,10 @@ done:
>  	pushl saved_context_eflags
>  	popfl
>  
> +	/* Saved in save_processor_state. */
> +	movl $saved_context, %eax
> +	lgdt saved_context_gdt_desc(%eax)
> +
>  	xorl	%eax, %eax
>  
>  	ret
> diff --git a/arch/x86/power/hibernate_asm_64.S b/arch/x86/power/hibernate_asm_64.S
> index 9356547..3c4469a 100644
> --- a/arch/x86/power/hibernate_asm_64.S
> +++ b/arch/x86/power/hibernate_asm_64.S
> @@ -139,6 +139,9 @@ ENTRY(restore_registers)
>  	pushq	pt_regs_flags(%rax)
>  	popfq
>  
> +	/* Saved in save_processor_state. */
> +	lgdt	saved_context_gdt_desc(%rax)
> +
>  	xorq	%rax, %rax
>  
>  	/* tell the hibernation core that we've just restored the memory */
> 
-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.