Commit-ID: 162ee5a8ab49be40d253f90e94aef712470a3a24 Gitweb: https://git.kernel.org/tip/162ee5a8ab49be40d253f90e94aef712470a3a24 Author: Sai Praneeth <sai.praneeth.prak...@intel.com> AuthorDate: Wed, 4 Apr 2018 12:34:19 -0700 Committer: Ingo Molnar <mi...@kernel.org> CommitDate: Thu, 5 Apr 2018 01:27:49 +0200
x86/mm: Fix bogus warning during EFI bootup, use boot_cpu_has() instead of this_cpu_has() in build_cr3_noflush() 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 <torva...@linux-foundation.org> Signed-off-by: Sai Praneeth Prakhya <sai.praneeth.prak...@intel.com> Cc: Andrew Morton <a...@linux-foundation.org> Cc: Andy Lutomirski <l...@kernel.org> Cc: Ard Biesheuvel <ard.biesheu...@linaro.org> Cc: Borislav Petkov <b...@alien8.de> Cc: Dave Hansen <dave.han...@intel.com> Cc: Lee Chun-Yi <j...@suse.com> Cc: Matt Fleming <m...@codeblueprint.co.uk> Cc: Michael S. Tsirkin <m...@redhat.com> Cc: Peter Zijlstra <a.p.zijls...@chello.nl> Cc: Peter Zijlstra <pet...@infradead.org> Cc: Ravi Shankar <ravi.v.shan...@intel.com> Cc: Ricardo Neri <ricardo.n...@intel.com> Cc: Thomas Gleixner <t...@linutronix.de> Cc: Tony Luck <tony.l...@intel.com> Cc: linux-...@vger.kernel.org Link: http://lkml.kernel.org/r/1522870459-7432-1-git-send-email-sai.praneeth.prak...@intel.com Signed-off-by: Ingo Molnar <mi...@kernel.org> --- arch/x86/include/asm/tlbflush.h | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/arch/x86/include/asm/tlbflush.h b/arch/x86/include/asm/tlbflush.h index 84137c22fdfa..6690cd3fc8b1 100644 --- a/arch/x86/include/asm/tlbflush.h +++ b/arch/x86/include/asm/tlbflush.h @@ -131,7 +131,12 @@ static inline unsigned long build_cr3(pgd_t *pgd, u16 asid) static inline unsigned long build_cr3_noflush(pgd_t *pgd, u16 asid) { VM_WARN_ON_ONCE(asid > MAX_ASID_AVAILABLE); - VM_WARN_ON_ONCE(!this_cpu_has(X86_FEATURE_PCID)); + /* + * Use boot_cpu_has() instead of this_cpu_has() as this function + * might be called during early boot. This should work even after + * boot because all CPU's the have same capabilities: + */ + VM_WARN_ON_ONCE(!boot_cpu_has(X86_FEATURE_PCID)); return __sme_pa(pgd) | kern_pcid(asid) | CR3_NOFLUSH; }
