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

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Date:	Fri, 11 Oct 2013 09:41:44 +0200
From:	Borislav Petkov <bp@...en8.de>
To:	Dave Young <dyoung@...hat.com>
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 Fri, Oct 11, 2013 at 02:24:37PM +0800, Dave Young wrote:
> But for current implementation from Boris, getting same mapping
> between diffrent kernel depends on same md order (same start and
> size for each one) How about using this mapping solution but at the
> same time for kexec kernel we also pass the virtual mappings via
> setup_data, only thing diffrent is we only need map the non boot
> region and just use the boot region size to ensure the other regions
> are mapped with same virtual address.

Actually, as hpa suggested, we will need to be passing the explicit
virtual addresses to the kexec kernel in case we change the mapping
algorithm in the future. So all should go through setup_data.

> OTOH, if we only passing ioremapped data without Boris's current patch
> the problem I worry about is how can we ensure the addresses are not
> used by other code before we mapping the in 2nd kernel efi_init.

Right, the old method of mapping EFI runtime regions used ioremap and
was mapping the regions in the same address space. Now we have reserved
a 64G in the VA space ending at -4G (i.e. 0xffff_ffff_0000_0000) which
is reserved only for EFI RT usage.

-- 
Regards/Gruss,
    Boris.

Sent from a fat crate under my desk. Formatting is fine.
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