linux-kernel - Re: [PATCH v4 1/5] efi: Introduce EFI

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Date:	Tue, 20 May 2014 07:16:22 +0100
From:	"Jan Beulich" <JBeulich@...e.com>
To:	"Daniel Kiper" <daniel.kiper@...cle.com>
Cc:	<david.vrabel@...rix.com>, <ian.campbell@...rix.com>,
	<stefano.stabellini@...citrix.com>, <jeremy@...p.org>,
	<matt.fleming@...el.com>, <x86@...nel.org>, <tglx@...utronix.de>,
	<xen-devel@...ts.xenproject.org>, <boris.ostrovsky@...cle.com>,
	<konrad.wilk@...cle.com>, <eshelton@...ox.com>, <mingo@...hat.com>,
	<mjg59@...f.ucam.org>, <linux-efi@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <hpa@...or.com>
Subject: Re: [PATCH v4 1/5] efi: Introduce EFI_DIRECT flag

>>> On 19.05.14 at 22:46, <daniel.kiper@...cle.com> wrote:
> On Mon, May 19, 2014 at 02:30:45PM +0100, Jan Beulich wrote:
>> >>> On 16.05.14 at 22:41, <daniel.kiper@...cle.com> wrote:
>> > @@ -457,6 +460,21 @@ void __init efi_free_boot_services(void)
>> >  	efi_unmap_memmap();
>> >  }
>> >
>> > +static void __init __iomem *efi_early_ioremap(resource_size_t phys_addr,
>> > +							unsigned long size)
>> > +{
>> > +	if (efi_enabled(EFI_DIRECT))
>> > +		return early_ioremap(phys_addr, size);
>> > +
>> > +	return (__force void __iomem *)phys_addr;
>>
>> Now that surely needs some explanation: I can't see how this can
>> ever be correct, Xen or not being completely irrelevant.
> 
> I hope that efi_enabled(EFI_DIRECT) is obvious. However, in case of
> !efi_enabled(EFI_DIRECT) some structures are created artificially
> and they live in virtual address space. So that is why they should
> not be mapped. If you wish I could add relevant comment here.

That would be the very minimum I suppose. But I wonder whether
you wouldn't be better off storing their physical addresses in the
first place (and then decide whether you can stay with early_ioremap()
or want/need to use early_memremap() if !EFI_DIRECT).

Jan

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