linux-kernel - Re: [PATCH, DEBUG] x86/32: Add small delay after resume

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Message-ID: <1434493541.2353.97.camel@spandruv-DESK3.jf.intel.com>
Date:	Tue, 16 Jun 2015 15:25:41 -0700
From:	Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Ingo Molnar <mingo@...nel.org>, mingo@...hat.com,
	tglx@...utronix.de, pavel@....cz, rjw@...ysocki.net,
	x86@...nel.org, linux-pm@...r.kernel.org,
	linux-kernel@...r.kernel.org, Denys Vlasenko <dvlasenk@...hat.com>,
	Andy Lutomirski <luto@...capital.net>,
	Borislav Petkov <bp@...en8.de>,
	Brian Gerst <brgerst@...il.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	"Kleen, Andi" <andi.kleen@...el.com>
Subject: Re: [PATCH, DEBUG] x86/32: Add small delay after resume

On Tue, 2015-06-16 at 14:33 -0700, H. Peter Anvin wrote:
> On 06/15/2015 09:10 AM, Srinivas Pandruvada wrote:
> >>
> >> So is it true that we always execute wakeup_pmode_return first after we return 
> >> from the BIOS?
> >>
> >> If so then the BIOS touching DS cannot be an issue, as we re-initialize all 
> >> segment selectors, which reloads the descriptors:
> >>
> >> ENTRY(wakeup_pmode_return)
> >> wakeup_pmode_return:
> >>         movw    $__KERNEL_DS, %ax
> >>         movw    %ax, %ss
> >>         movw    %ax, %ds
> >>         movw    %ax, %es
> >>         movw    %ax, %fs
> >>         movw    %ax, %gs
> >>
> >>         # reload the gdt, as we need the full 32 bit address
> >>         lidt    saved_idt
> >>         lldt    saved_ldt
> >>         ljmp    $(__KERNEL_CS), $1f
> >>
> 
> Where does the GDT get initialized?
In wakeup_start
During acpi_sleep_prepare we set a 32 bit FW waking vector which points
to wakeup_start.

Thanks,
Srinivas
> 
> 	-hpa
> 
> 
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