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    Subject[PATCH AUTOSEL 5.3 49/89] efi/x86: Do not clean dummy variable in kexec path
    Date
    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 a7189a3b4d70f..3304f61538a26 100644
    --- a/arch/x86/platform/efi/efi.c
    +++ b/arch/x86/platform/efi/efi.c
    @@ -894,9 +894,6 @@ 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
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