From 1a78d93750bb5f61abdc59a91fc3bd06a214542a Mon Sep 17 00:00:00 2001 From: Andi Kleen Date: Fri, 20 Mar 2015 10:11:23 -0700 Subject: [PATCH] perf/x86/intel: Streamline LBR MSR handling in PMI The perf PMI currently does unnecessary MSR accesses when LBRs are enabled. We use LBR freezing, or when in callstack mode force the LBRs to only filter on ring 3. So there is no need to disable the LBRs explicitely in the PMI handler. Also we always unnecessarily rewrite LBR_SELECT in the LBR handler, even though it can never change. 5) | /* write_msr: MSR_LBR_SELECT(1c8), value 0 */ 5) | /* read_msr: MSR_IA32_DEBUGCTLMSR(1d9), value 1801 */ 5) | /* write_msr: MSR_IA32_DEBUGCTLMSR(1d9), value 1801 */ 5) | /* write_msr: MSR_CORE_PERF_GLOBAL_CTRL(38f), value 70000000f */ 5) | /* write_msr: MSR_CORE_PERF_GLOBAL_CTRL(38f), value 0 */ 5) | /* write_msr: MSR_LBR_SELECT(1c8), value 0 */ 5) | /* read_msr: MSR_IA32_DEBUGCTLMSR(1d9), value 1801 */ 5) | /* write_msr: MSR_IA32_DEBUGCTLMSR(1d9), value 1801 */ This patch: - Avoids disabling already frozen LBRs unnecessarily in the PMI - Avoids changing LBR_SELECT in the PMI Signed-off-by: Andi Kleen Signed-off-by: Peter Zijlstra (Intel) Cc: eranian@google.com Link: http://lkml.kernel.org/r/1426871484-21285-1-git-send-email-andi@firstfloor.org Signed-off-by: Ingo Molnar --- Reading git-format-patch failed