linux-kernel - Re: [PATCH 1/2] x86/efi: Correct a tiny mistake in code comment

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Date:   Wed, 8 Mar 2017 16:45:13 +0800
From:   Baoquan He <bhe@...hat.com>
To:     Dave Young <dyoung@...hat.com>
Cc:     linux-kernel@...r.kernel.org, linux-efi@...r.kernel.org,
        thgarnie@...gle.com, keescook@...omium.org, tglx@...utronix.de,
        mingo@...hat.com, hpa@...or.com, x86@...nel.org,
        akpm@...ux-foundation.org, bp@...e.de
Subject: Re: [PATCH 1/2] x86/efi: Correct a tiny mistake in code comment

Forgot cc to Boris, add him.

On 03/08/17 at 04:18pm, Dave Young wrote:
> On 03/08/17 at 03:47pm, Baoquan He wrote:
> > EFI allocate runtime services regions down from EFI_VA_START, -4G.
> > It should be top-down handling.
> > 
> > Signed-off-by: Baoquan He <bhe@...hat.com>
> > ---
> >  arch/x86/platform/efi/efi_64.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/arch/x86/platform/efi/efi_64.c b/arch/x86/platform/efi/efi_64.c
> > index a4695da..6cbf9e0 100644
> > --- a/arch/x86/platform/efi/efi_64.c
> > +++ b/arch/x86/platform/efi/efi_64.c
> > @@ -47,7 +47,7 @@
> >  #include <asm/pgalloc.h>
> >  
> >  /*
> > - * We allocate runtime services regions bottom-up, starting from -4G, i.e.
> > + * We allocate runtime services regions top-down, starting from -4G, i.e.
> 
> Baoquan, I think original bottom-up is right, it is just considering
> -68G as up, see the x86_64 mm.txt. We regard vmalloc as higher address
> although from mathematics view it is lower then positive addresses.

Thanks for reviewing!

I am not sure. Just in efi_map_region() it gets the starting va to map
'size' big of region by below code:
	efi_va -= size;

-4G and -68G just a trick which makes people understand easily, still we
think kernel text mapping region is in higher addr area then vmalloc. I
personnally think.

Thanks
Baoquan