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

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Message-ID: <20170309013852.GD12600@dhcp-128-65.nay.redhat.com>
Date:   Thu, 9 Mar 2017 09:38:52 +0800
From:   Dave Young <dyoung@...hat.com>
To:     Baoquan He <bhe@...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

Hi,

On 03/08/17 at 04:45pm, Baoquan He wrote:
> 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.

I understand your points, there is not right or wrong. So I think drop
the words like the change in your V2 looks good.

Thanks
Dave