linux-kernel - [PATCH] do not clean dummy variable in kexec path

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Date:   Mon, 5 Aug 2019 16:35:53 +0800
From:   Dave Young <dyoung@...hat.com>
To:     linux-efi@...r.kernel.org, ard.biesheuvel@...aro.org
Cc:     kexec@...ts.infradead.org, linux-kernel@...r.kernel.org,
        matthewgarrett@...gle.com, bhsharma@...hat.com
Subject: [PATCH] do not clean dummy variable in kexec path

kexec reboot fails randomly in UEFI based kvm guest.  The firmware
just reset 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 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 dummy object.

Drop efi_delete_dummy_variable so that kexec reboot can work.

Signed-off-by: Dave Young <dyoung@...hat.com>
---
 arch/x86/platform/efi/efi.c |    3 ---
 1 file changed, 3 deletions(-)

--- linux-x86.orig/arch/x86/platform/efi/efi.c
+++ linux-x86/arch/x86/platform/efi/efi.c
@@ -894,9 +894,6 @@ static void __init kexec_enter_virtual_m

 	if (efi_enabled(EFI_OLD_MEMMAP) && (__supported_pte_mask & _PAGE_NX))
 		runtime_code_page_mkexec();
-
-	/* clean DUMMY object */
-	efi_delete_dummy_variable();
 #endif
 }