linux-kernel - [PATCH 4.4 16/46] efi/x86: Do not clean dummy variable in kexec path

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Date:   Mon,  4 Nov 2019 22:44:47 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, 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>, Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.4 16/46] efi/x86: Do not clean dummy variable in kexec path

From: Dave Young <dyoung@...hat.com>

[ Upstream commit 2ecb7402cfc7f22764e7bbc80790e66eadb20560 ]

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>
Signed-off-by: Sasha Levin <sashal@...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 ad285404ea7f5..4bc352fc08f19 100644
--- a/arch/x86/platform/efi/efi.c
+++ b/arch/x86/platform/efi/efi.c
@@ -859,9 +859,6 @@ 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
 }
 
-- 
2.20.1