linux-kernel - Re: [PATCH 3/3] efi: Make efi virtual runtime map passing more robust

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Date:	Wed, 18 Dec 2013 17:07:57 +0800
From:	Dave Young <dyoung@...hat.com>
To:	Borislav Petkov <bp@...en8.de>
Cc:	Linux EFI <linux-efi@...r.kernel.org>, X86 ML <x86@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Borislav Petkov <bp@...e.de>,
	Matt Fleming <matt@...sole-pimps.org>,
	Matthew Garrett <mjg59@...f.ucam.org>,
	"H. Peter Anvin" <hpa@...or.com>,
	James Bottomley <James.Bottomley@...senPartnership.com>,
	Vivek Goyal <vgoyal@...hat.com>,
	Toshi Kani <toshi.kani@...com>,
	Arjan van de Ven <arjan@...ux.intel.com>
Subject: Re: [PATCH 3/3] efi: Make efi virtual runtime map passing more robust

On 12/17/13 at 12:36am, Borislav Petkov wrote:
> From: Borislav Petkov <bp@...e.de>
> 
> Currently, running SetVirtualAddressMap() and passing the physical
> address of the virtual map array was working only by a lucky coincidence
> because the memory was present in the EFI page table too. Until Toshi
> went and booted this on a big HP box - the krealloc() manner of resizing
> the memmap we're doing did allocate from such physical addresses which
> were not mapped anymore and boom:
> 
> http://lkml.kernel.org/r/1386806463.1791.295.camel@misato.fc.hp.com
> 
> One way to take care of that issue is to reimplement the krealloc thing
> but with pages. We start with contiguous pages of order 1, i.e. 2 pages,
> and when we deplete that memory (shouldn't happen all that often but you
> know firmware) we realloc the next power-of-two pages.

How about firstly count the md numbers in the 1st loop, then get/roundup
the total size, alloc the pages, map the mds one by one in another loop.

Thanks
Dave
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