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

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Message-ID: <20160613120322.GA2658@codeblueprint.co.uk>
Date:	Mon, 13 Jun 2016 13:03:22 +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 Thu, 09 Jun, at 11:16:40AM, Tom Lendacky wrote:
> 
> So maybe something along the lines of an enum that would have entries
> (initially) like KERNEL_DATA (equal to zero) and EFI_DATA. Others could
> be added later as needed.
 
Sure, that works for me, though maybe BOOT_DATA would be more
applicable considering the devicetree case too.

> Would you then want to allow the protection attributes to be updated
> by architecture specific code through something like a __weak function?
> In the x86 case I can add this function as a non-SME specific function
> that would initially just have the SME-related mask modification in it.

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);
}