From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.kernel.org ([198.145.29.99]:54408 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1423441AbeE1LHc (ORCPT ); Mon, 28 May 2018 07:07:32 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Linus Torvalds , Sai Praneeth Prakhya , Andrew Morton , Andy Lutomirski , Ard Biesheuvel , Borislav Petkov , Dave Hansen , Lee Chun-Yi , Matt Fleming , "Michael S. Tsirkin" , Peter Zijlstra , Peter Zijlstra , Ravi Shankar , Ricardo Neri , Thomas Gleixner , Tony Luck , linux-efi@vger.kernel.org, Ingo Molnar , Sasha Levin Subject: [PATCH 4.16 078/272] x86/mm: Fix bogus warning during EFI bootup, use boot_cpu_has() instead of this_cpu_has() in build_cr3_noflush() Date: Mon, 28 May 2018 12:01:51 +0200 Message-Id: <20180528100247.645864018@linuxfoundation.org> In-Reply-To: <20180528100240.256525891@linuxfoundation.org> References: <20180528100240.256525891@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: stable-owner@vger.kernel.org List-ID: 4.16-stable review patch. If anyone has any objections, please let me know. ------------------ From: Sai Praneeth [ 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 Signed-off-by: Sai Praneeth Prakhya Cc: Andrew Morton Cc: Andy Lutomirski Cc: Ard Biesheuvel Cc: Borislav Petkov Cc: Dave Hansen Cc: Lee Chun-Yi Cc: Matt Fleming Cc: Michael S. Tsirkin Cc: Peter Zijlstra Cc: Peter Zijlstra Cc: Ravi Shankar Cc: Ricardo Neri Cc: Thomas Gleixner Cc: Tony Luck 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 Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- arch/x86/include/asm/tlbflush.h | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) --- a/arch/x86/include/asm/tlbflush.h +++ b/arch/x86/include/asm/tlbflush.h @@ -131,7 +131,12 @@ static inline unsigned long build_cr3(pg 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; }