linux-kernel - Re: [RFC PATCH v1 10/18] x86/efi: Access EFI related tables in the clear

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Date:	Mon, 13 Jun 2016 13:34:52 +0100
From:	Matt Fleming <matt@...eblueprint.co.uk>
To:	Tom Lendacky <thomas.lendacky@....com>
Cc:	Borislav Petkov <bp@...en8.de>,
	Leif Lindholm <leif.lindholm@...aro.org>,
	Mark Salter <msalter@...hat.com>,
	Daniel Kiper <daniel.kiper@...cle.com>,
	linux-arch@...r.kernel.org, linux-efi@...r.kernel.org,
	kvm@...r.kernel.org, linux-doc@...r.kernel.org, x86@...nel.org,
	linux-kernel@...r.kernel.org, kasan-dev@...glegroups.com,
	linux-mm@...ck.org, iommu@...ts.linux-foundation.org,
	Radim Krčmář <rkrcmar@...hat.com>,
	Arnd Bergmann <arnd@...db.de>,
	Jonathan Corbet <corbet@....net>,
	Joerg Roedel <joro@...tes.org>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	Paolo Bonzini <pbonzini@...hat.com>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Andrey Ryabinin <aryabinin@...tuozzo.com>,
	Alexander Potapenko <glider@...gle.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Dmitry Vyukov <dvyukov@...gle.com>,
	Ard Biesheuvel <ard.biesheuvel@...aro.org>
Subject: Re: [RFC PATCH v1 10/18] x86/efi: Access EFI related tables in the
 clear

On Mon, 13 Jun, at 01:03:22PM, Matt Fleming wrote:
> 
> Would we need a new function? Couldn't we just have a new
> FIXMAP_PAGE_* constant? e.g. would something like this work?
> 
> ---
> 
> enum memremap_owner {
> 	KERNEL_DATA = 0,
> 	BOOT_DATA,
> };
> 
> void __init *
> early_memremap(resource_size_t phys_addr, unsigned long size,
> 	       enum memremap_owner owner)
> {
> 	pgprot_t prot;
> 
> 	switch (owner) {
> 	case BOOT_DATA:
> 		prot = FIXMAP_PAGE_BOOT;
> 		break;
> 	case KERNEL_DATA:	/* FALLTHROUGH */
> 	default:
> 		prot = FIXMAP_PAGE_NORMAL;
> 		
> 	}
> 
> 	return (__force void *)__early_ioremap(phys_addr, size, prot);
> }

Although it occurs to me that if there's a trivial 1:1 mapping between
memremap_owner and FIXMAP_PAGE_* we might as well just add a new
early_memremap_boot() that uses the correct FIXMAP_PAGE_* constant,
akin to early_memremap_ro().