linux-kernel - Re: [PATCH] x86/efi: Setup separate EFI page tables in kexec paths

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Message-ID: <20160121205815.GI2510@codeblueprint.co.uk>
Date:	Thu, 21 Jan 2016 20:58:15 +0000
From:	Matt Fleming <matt@...eblueprint.co.uk>
To:	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
Cc:	Ingo Molnar <mingo@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H . Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org,
	linux-efi@...r.kernel.org,
	Raghavendra K T <raghavendra.kt@...ux.vnet.ibm.com>,
	Dave Young <dyoung@...hat.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Borislav Petkov <bp@...en8.de>
Subject: Re: [PATCH] x86/efi: Setup separate EFI page tables in kexec paths

On Fri, 22 Jan, at 01:03:32AM, Srikar Dronamraju wrote:
> * Matt Fleming <matt@...eblueprint.co.uk> [2016-01-21 14:11:59]:
> 
> > The switch to using a new dedicated page table for EFI runtime calls
> > in commit commit 67a9108ed431 ("x86/efi: Build our own page table
> > structures") failed to take into account changes required for the
> > kexec code paths, which are unfortunately duplicated in the EFI code.
> > 
> > Call the allocation and setup functions in kexec_enter_virtual_mode()
> > just like we do for __efi_enter_virtual_mode() to avoid hitting
> > NULL-pointer dereferences when making EFI runtime calls.
> > 
> > At the very least, the call to efi_setup_page_tables() should have
> > existed for kexec before commit 67a9108ed431. Things just magically
> > worked because we were actually using the kernel's page tables that
> > contained the required mappings.
> > 
> > Reported-by: Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
> > Cc: Raghavendra K T <raghavendra.kt@...ux.vnet.ibm.com>
> > Cc: Dave Young <dyoung@...hat.com>
> > Cc: Ingo Molnar <mingo@...nel.org>
> > Cc: Linus Torvalds <torvalds@...ux-foundation.org>
> > Cc: Borislav Petkov <bp@...en8.de>
> > Signed-off-by: Matt Fleming <matt@...eblueprint.co.uk>
> 
> Applied this patch on top of tip/x86/efi and was able to build and boot
> the kernel.

Fantastic, thanks for testing!

Ingo, this commit should unblock the EFI changes for v4.5.