From mboxrd@z Thu Jan  1 00:00:00 1970
From: "H. Peter Anvin" <hpa-YMNOUZJC4hwAvxtiuMwx3w@public.gmane.org>
Subject: Re: [PATCH -v2] EFI: Runtime services virtual mapping
Date: Wed, 02 Oct 2013 11:46:44 -0700
Message-ID: <524C6A14.40905@zytor.com>
References: <20130921113929.GB1587@pd.tnic> <20130922123515.GA7476@dhcp-16-126.nay.redhat.com> <20130922133722.GC28718@pd.tnic> <1ba7eca6-419c-4181-9927-9ba0927a6abf@email.android.com> <20130924025209.GA5561@dhcp-16-126.nay.redhat.com> <2d27a1bc-eabf-4d45-8303-27ae58511b11@email.android.com> <20131002100426.GB20568@pd.tnic> <524C3F38.6050507@zytor.com> <20131002170522.GA20647@pd.tnic> <524C58A3.4090704@zytor.com> <20131002184229.GE20568@pd.tnic>
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To: Borislav Petkov <bp-Gina5bIWoIWzQB+pC5nmwQ@public.gmane.org>
Cc: Dave Young <dyoung-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>, X86 ML <x86-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>, LKML <linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>, Borislav Petkov <bp-l3A5Bk7waGM@public.gmane.org>, Matt Fleming <matt-HNK1S37rvNbeXh+fF434Mdi2O/JbrIOy@public.gmane.org>, Matthew Garrett <mjg59-1xO5oi07KQx4cg9Nei1l7Q@public.gmane.org>, James Bottomley <James.Bottomley-d9PhHud1JfjCXq6kfMZ53/egYHeGw8Jk@public.gmane.org>, Vivek Goyal <vgoyal-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>, linux-efi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
List-Id: linux-efi@vger.kernel.org

On 10/02/2013 11:42 AM, Borislav Petkov wrote:
> 
> Yes, so the alignment has to be such that both PA and VA are the same
> amount of 4K pages away from the next 2M boundary, to put it bluntly.
> 
> I have a couple of ideas on how to do that.
> 

It's pretty straightforward - just drop the starting address to proper
alignment after you subtract the size.

	-hpa