From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753196AbeBJXlV (ORCPT ); Sat, 10 Feb 2018 18:41:21 -0500 Received: from smtp-fw-33001.amazon.com ([207.171.190.10]:60670 "EHLO smtp-fw-33001.amazon.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752926AbeBJXjs (ORCPT ); Sat, 10 Feb 2018 18:39:48 -0500 X-IronPort-AV: E=Sophos;i="5.46,492,1511827200"; d="scan'208";a="719069391" From: David Woodhouse To: tglx@linutronix.de, karahmed@amazon.de, sironi@amazon.de, x86@kernel.org, kvm@vger.kernel.org, torvalds@linux-foundation.org, pbonzini@redhat.com, linux-kernel@vger.kernel.org, bp@alien8.de, peterz@infradead.org, jmattson@google.com, rkrcmar@redhat.com, arjan.van.de.ven@intel.com, dave.hansen@intel.com Subject: [PATCH v2 2/6] Revert "x86/speculation: Simplify indirect_branch_prediction_barrier()" Date: Sat, 10 Feb 2018 23:39:23 +0000 Message-Id: <1518305967-31356-3-git-send-email-dwmw@amazon.co.uk> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1518305967-31356-1-git-send-email-dwmw@amazon.co.uk> References: <1518305967-31356-1-git-send-email-dwmw@amazon.co.uk> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This reverts commit 64e16720ea0879f8ab4547e3b9758936d483909b. We cannot call C functions like that, without marking all the call-clobbered registers as, well, clobbered. We might have got away with it for now because the __ibp_barrier() function was *fairly* unlikely to actually use any other registers. But no. Just no. Signed-off-by: David Woodhouse --- arch/x86/include/asm/nospec-branch.h | 13 +++++++++---- arch/x86/include/asm/processor.h | 3 --- arch/x86/kernel/cpu/bugs.c | 6 ------ 3 files changed, 9 insertions(+), 13 deletions(-) diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h index 4d57894..300cc15 100644 --- a/arch/x86/include/asm/nospec-branch.h +++ b/arch/x86/include/asm/nospec-branch.h @@ -164,10 +164,15 @@ static inline void vmexit_fill_RSB(void) static inline void indirect_branch_prediction_barrier(void) { - alternative_input("", - "call __ibp_barrier", - X86_FEATURE_USE_IBPB, - ASM_NO_INPUT_CLOBBER("eax", "ecx", "edx", "memory")); + asm volatile(ALTERNATIVE("", + "movl %[msr], %%ecx\n\t" + "movl %[val], %%eax\n\t" + "movl $0, %%edx\n\t" + "wrmsr", + X86_FEATURE_USE_IBPB) + : : [msr] "i" (MSR_IA32_PRED_CMD), + [val] "i" (PRED_CMD_IBPB) + : "eax", "ecx", "edx", "memory"); } #endif /* __ASSEMBLY__ */ diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h index 513f960..99799fb 100644 --- a/arch/x86/include/asm/processor.h +++ b/arch/x86/include/asm/processor.h @@ -969,7 +969,4 @@ bool xen_set_default_idle(void); void stop_this_cpu(void *dummy); void df_debug(struct pt_regs *regs, long error_code); - -void __ibp_barrier(void); - #endif /* _ASM_X86_PROCESSOR_H */ diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c index 71949bf..61152aa 100644 --- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -337,9 +337,3 @@ ssize_t cpu_show_spectre_v2(struct device *dev, spectre_v2_module_string()); } #endif - -void __ibp_barrier(void) -{ - __wrmsr(MSR_IA32_PRED_CMD, PRED_CMD_IBPB, 0); -} -EXPORT_SYMBOL_GPL(__ibp_barrier); -- 2.7.4