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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Dave Young <dyoung@redhat.com>,
        Ard Biesheuvel <ard.biesheuvel@linaro.org>,
        Matthew Garrett <mjg59@google.com>,
        Ben Dooks <ben.dooks@codethink.co.uk>,
        Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>,
        Jerry Snitselaar <jsnitsel@redhat.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Lukas Wunner <lukas@wunner.de>, Lyude Paul <lyude@redhat.com>,
        Octavian Purdila <octavian.purdila@intel.com>,
        Peter Jones <pjones@redhat.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Scott Talbert <swt@techie.net>,
        Thomas Gleixner <tglx@linutronix.de>,
        linux-efi@vger.kernel.org, linux-integrity@vger.kernel.org,
        Ingo Molnar <mingo@kernel.org>, Sasha Levin <sashal@kernel.org>
Subject: [PATCH 4.19 082/149] efi/x86: Do not clean dummy variable in kexec path
Date:   Mon,  4 Nov 2019 22:44:35 +0100
Message-Id: <20191104212142.341008793@linuxfoundation.org>
In-Reply-To: <20191104212126.090054740@linuxfoundation.org>
References: <20191104212126.090054740@linuxfoundation.org>
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From: Dave Young <dyoung@redhat.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@redhat.com>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Acked-by: Matthew Garrett <mjg59@google.com>
Cc: Ben Dooks <ben.dooks@codethink.co.uk>
Cc: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Cc: Jerry Snitselaar <jsnitsel@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Lukas Wunner <lukas@wunner.de>
Cc: Lyude Paul <lyude@redhat.com>
Cc: Octavian Purdila <octavian.purdila@intel.com>
Cc: Peter Jones <pjones@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Scott Talbert <swt@techie.net>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-efi@vger.kernel.org
Cc: linux-integrity@vger.kernel.org
Link: https://lkml.kernel.org/r/20191002165904.8819-8-ard.biesheuvel@linaro.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.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 9061babfbc83d..335a62e74a2e9 100644
--- a/arch/x86/platform/efi/efi.c
+++ b/arch/x86/platform/efi/efi.c
@@ -893,9 +893,6 @@ 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