linux-kernel - [tip: efi/urgent] efi/x86: Do not clean dummy variable in kexec path

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Date:   Mon, 07 Oct 2019 14:49:09 -0000
From:   "tip-bot2 for Dave Young" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     Dave Young <dyoung@...hat.com>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Matthew Garrett <mjg59@...gle.com>,
        Ben Dooks <ben.dooks@...ethink.co.uk>,
        Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>,
        Jerry Snitselaar <jsnitsel@...hat.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Lukas Wunner <lukas@...ner.de>, Lyude Paul <lyude@...hat.com>,
        Octavian Purdila <octavian.purdila@...el.com>,
        Peter Jones <pjones@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Scott Talbert <swt@...hie.net>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-efi@...r.kernel.org, linux-integrity@...r.kernel.org,
        Ingo Molnar <mingo@...nel.org>, Borislav Petkov <bp@...en8.de>,
        linux-kernel@...r.kernel.org
Subject: [tip: efi/urgent] efi/x86: Do not clean dummy variable in kexec path

The following commit has been merged into the efi/urgent branch of tip:

Commit-ID:     2ecb7402cfc7f22764e7bbc80790e66eadb20560
Gitweb:        https://git.kernel.org/tip/2ecb7402cfc7f22764e7bbc80790e66eadb20560
Author:        Dave Young <dyoung@...hat.com>
AuthorDate:    Wed, 02 Oct 2019 18:59:04 +02:00
Committer:     Ingo Molnar <mingo@...nel.org>
CommitterDate: Mon, 07 Oct 2019 15:24:36 +02:00

efi/x86: Do not clean dummy variable in kexec path

kexec reboot fails randomly in UEFI based KVM guest.  The firmware
just resets while calling efi_delete_dummy_variable();  Unfortunately
I don't know how to debug the firmware, it is also possible a potential
problem on real hardware as well although nobody reproduced it.

The intention of the efi_delete_dummy_variable is to trigger garbage collection
when entering virtual mode.  But SetVirtualAddressMap can only run once
for each physical reboot, thus kexec_enter_virtual_mode() is not necessarily
a good place to clean a dummy object.

Drop the efi_delete_dummy_variable so that kexec reboot can work.

Signed-off-by: Dave Young <dyoung@...hat.com>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@...aro.org>
Acked-by: Matthew Garrett <mjg59@...gle.com>
Cc: Ben Dooks <ben.dooks@...ethink.co.uk>
Cc: Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
Cc: Jerry Snitselaar <jsnitsel@...hat.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Lukas Wunner <lukas@...ner.de>
Cc: Lyude Paul <lyude@...hat.com>
Cc: Octavian Purdila <octavian.purdila@...el.com>
Cc: Peter Jones <pjones@...hat.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Scott Talbert <swt@...hie.net>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: linux-efi@...r.kernel.org
Cc: linux-integrity@...r.kernel.org
Link: https://lkml.kernel.org/r/20191002165904.8819-8-ard.biesheuvel@linaro.org
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 arch/x86/platform/efi/efi.c | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/arch/x86/platform/efi/efi.c b/arch/x86/platform/efi/efi.c
index c202e1b..425e025 100644
--- a/arch/x86/platform/efi/efi.c
+++ b/arch/x86/platform/efi/efi.c
@@ -917,9 +917,6 @@ static void __init kexec_enter_virtual_mode(void)
 
 	if (efi_enabled(EFI_OLD_MEMMAP) && (__supported_pte_mask & _PAGE_NX))
 		runtime_code_page_mkexec();
-
-	/* clean DUMMY object */
-	efi_delete_dummy_variable();
 #endif
 }