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[ Upstream commit 162ee5a8ab49be40d253f90e94aef712470a3a24 ] Linus reported the following boot warning: WARNING: CPU: 0 PID: 0 at arch/x86/include/asm/tlbflush.h:134 load_new_mm_cr3+0x114/0x170 [...] Call Trace: switch_mm_irqs_off+0x267/0x590 switch_mm+0xe/0x20 efi_switch_mm+0x3e/0x50 efi_enter_virtual_mode+0x43f/0x4da start_kernel+0x3bf/0x458 secondary_startup_64+0xa5/0xb0 ... after merging: 03781e40890c: x86/efi: Use efi_switch_mm() rather than manually twiddling with %cr3 When the platform supports PCID and if CONFIG_DEBUG_VM=y is enabled, build_cr3_noflush() (called via switch_mm()) does a sanity check to see if X86_FEATURE_PCID is set. Presently, build_cr3_noflush() uses "this_cpu_has(X86_FEATURE_PCID)" to perform the check but this_cpu_has() works only after SMP is initialized (i.e. per cpu cpu_info's should be populated) and this happens to be very late in the boot process (during rest_init()). As efi_runtime_services() are called during (early) kernel boot time and run time, modify build_cr3_noflush() to use boot_cpu_has() all the time. As suggested by Dave Hansen, this should be OK because all CPU's have same capabilities on x86. With this change the warning is fixed. ( Dave also suggested that we put a warning in this_cpu_has() if it's used early in the boot process. This is still work in progress as it affects MCE. ) Reported-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Sai Praneeth Prakhya <sai.praneeth.prakhya@intel.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Andy Lutomirski <luto@kernel.org> Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org> Cc: Borislav Petkov <bp@alien8.de> Cc: Dave Hansen <dave.hansen@intel.com> Cc: Lee Chun-Yi <jlee@suse.com> Cc: Matt Fleming <matt@codeblueprint.co.uk> Cc: Michael S. Tsirkin <mst@redhat.com> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Ravi Shankar <ravi.v.shankar@intel.com> Cc: Ricardo Neri <ricardo.neri@intel.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Tony Luck <tony.luck@intel.com> Cc: linux-efi@vger.kernel.org Link: http://lkml.kernel.org/r/1522870459-7432-1-git-send-email-sai.praneeth.prakhya@intel.com Signed-off-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Sasha Levin <alexander.levin@microsoft.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.