linux-kernel - Re: [PATCH 12/12] EFI: Runtime services virtual mapping

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Date:	Wed, 23 Oct 2013 20:51:31 +0800
From:	Dave Young <dyoung@...hat.com>
To:	Borislav Petkov <bp@...en8.de>
Cc:	Matt Fleming <matt@...sole-pimps.org>, X86 ML <x86@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Borislav Petkov <bp@...e.de>,
	Matthew Garrett <mjg59@...f.ucam.org>,
	"H. Peter Anvin" <hpa@...or.com>,
	James Bottomley <James.Bottomley@...senPartnership.com>,
	Vivek Goyal <vgoyal@...hat.com>, linux-efi@...r.kernel.org,
	fwts-devel@...ts.ubuntu.com
Subject: Re: [PATCH 12/12] EFI: Runtime services virtual mapping

On 10/23/13 at 02:25pm, Borislav Petkov wrote:
> On Wed, Oct 23, 2013 at 10:17:31AM +0800, Dave Young wrote:
> > The reason is that I only pass runtime regions from 1st kernel to
> > kexec kernel, your efi mapping function uses the region size to
> > determin the virtual address from top to down. Because the passed-in
> > md ranges in kexec kernel are different from ranges booting from
> > firmware so the virtual address will be different.
> 
> Well, this shouldn't be because SetVirtualAddressMap has already fixed
> the virtual addresses for us. And if they're different, then runtime
> services won't work anyway. Or am I missing something...?

Maybe I did not explain clear enough.
Say first kernel mapping below regions:
Region A (boot service):phys_start_a size_a -> virt_start_a size_a
Region B (runtime):	phys_start_b size_b -> virt_start_b size_b

I will pass Range B into 2nd kernel
(phys_start_b, size_b, virt_start_b)

In kexed 2nd kernel, phys_start_b need to be mapped to virt_start_b
Simply use efi_map_region from your patch does not work because it
will map phys_start_b to a different virt address, isn't it?

So I need simply map according to the kexec passed in mapping addr.

Thanks
Dave
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