From patchwork Fri May 20 14:37:37 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Uros Bizjak X-Patchwork-Id: 12856879 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id C06FEC433F5 for ; Fri, 20 May 2022 14:37:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1350387AbiETOh4 (ORCPT ); Fri, 20 May 2022 10:37:56 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58274 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1350374AbiETOhx (ORCPT ); Fri, 20 May 2022 10:37:53 -0400 Received: from mail-ed1-x52f.google.com (mail-ed1-x52f.google.com [IPv6:2a00:1450:4864:20::52f]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C4D7117067F; Fri, 20 May 2022 07:37:52 -0700 (PDT) Received: by mail-ed1-x52f.google.com with SMTP id i40so11049873eda.7; Fri, 20 May 2022 07:37:52 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=SNXNCKWjPv4BzE2CH3tp7uy8+YvTS4PKnxAxp9Lue+o=; b=SSe/chN/e6h9trSK8Krz+duBeXvMclM1sRT+Iru9saimzJrMhlUPrvfU/ttXKXagY9 hgeeYUyv1Ogtfg5+mjSvEEQps40cP+a3+rXBZn25LpxrjEtfVUU1n6w5o2rVK8ZemKlC WYI7APijNeAbks77ldOUbvOfWFwgDSs8jph3JM0gVKGX+APDgaNaYH1TXhg4ov6B9eU7 oNS43AMy2iBAYP0l5VtQxk0XLYm1o1aLfXeonUSYGm5VqQ7GIuitl4G1Z54nx4iTzh5u qtZSwC/OtMINfebalIfiDeHPQCqdmo6j8k84lGwwEjMlYRT05gTlDlZEfDgY76owJUnH MUVw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=SNXNCKWjPv4BzE2CH3tp7uy8+YvTS4PKnxAxp9Lue+o=; b=YGCKiVz01HN/bkCZCgJFa0HkXCRbnqPxYi68aDzRQr2IFe2zYy0X0Qk72droR+F6Tn tT/uk9cFDdsestb5Dd0NrxKJBL9CxB9Tj0G1Mun66eHhmRaTn4vnyjhYkplRAYwqllvc 0c73L29z7527UWOPkTqdZy2dSfBubkOyqFYNMfsUEM/Ou1sypGRPBxbtWUtbsPq8/dhm RXreXU6b1t8XN6cHFFjSPkkRat8lvawb/y0xqXAxqIZ4KJ4DzLjNAdUKGwoJQn/FxNZB la+jm67GRn3biKlGWhgLqNWLFpjVFZbrxMMJkVdUGoFlAJWqhmXFqDaNOoSNrP+Vq66N hx6w== X-Gm-Message-State: AOAM530EIKLkACyMwe81Fs0SEPcszmbcnXmhx4/e0sHZ3AAvTqppgPBu svtQBRuXCKIkCzSDt2RB5tD+yGCtA+c= X-Google-Smtp-Source: ABdhPJx6mzqfScSh0Z9xjgretxGpNUY4ve2pR1Vl4SldM+M92rxx0N+4cPlFRlvzN4BY89Po6tGdtw== X-Received: by 2002:aa7:c506:0:b0:42a:b067:cbe7 with SMTP id o6-20020aa7c506000000b0042ab067cbe7mr11261756edq.4.1653057470979; Fri, 20 May 2022 07:37:50 -0700 (PDT) Received: from localhost.localdomain (93-103-18-160.static.t-2.net. [93.103.18.160]) by smtp.gmail.com with ESMTPSA id cf5-20020a170906b2c500b006feb8cebbbfsm2473ejb.6.2022.05.20.07.37.50 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 20 May 2022 07:37:50 -0700 (PDT) From: Uros Bizjak To: kvm@vger.kernel.org, linux-kernel@vger.kernel.org Cc: Uros Bizjak , Paolo Bonzini , Sean Christopherson , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel Subject: [PATCH v2] KVM: VMX: Use try_cmpxchg64 in pi_try_set_control Date: Fri, 20 May 2022 16:37:37 +0200 Message-Id: <20220520143737.62513-1-ubizjak@gmail.com> X-Mailer: git-send-email 2.35.3 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org Use try_cmpxchg64 instead of cmpxchg64 (*ptr, old, new) != old in pi_try_set_control. cmpxchg returns success in ZF flag, so this change saves a compare after cmpxchg (and related move instruction in front of cmpxchg): b9: 88 44 24 60 mov %al,0x60(%rsp) bd: 48 89 c8 mov %rcx,%rax c0: c6 44 24 62 f2 movb $0xf2,0x62(%rsp) c5: 48 8b 74 24 60 mov 0x60(%rsp),%rsi ca: f0 49 0f b1 34 24 lock cmpxchg %rsi,(%r12) d0: 48 39 c1 cmp %rax,%rcx d3: 75 cf jne a4 patched: c1: 88 54 24 60 mov %dl,0x60(%rsp) c5: c6 44 24 62 f2 movb $0xf2,0x62(%rsp) ca: 48 8b 54 24 60 mov 0x60(%rsp),%rdx cf: f0 48 0f b1 13 lock cmpxchg %rdx,(%rbx) d4: 75 d5 jne ab Signed-off-by: Uros Bizjak Cc: Paolo Bonzini Cc: Sean Christopherson Cc: Vitaly Kuznetsov Cc: Wanpeng Li Cc: Jim Mattson Cc: Joerg Roedel Reported-by: kernel test robot --- v2: - use address of local variable &old The patch is agains tip tree. --- arch/x86/kvm/vmx/posted_intr.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/x86/kvm/vmx/posted_intr.c b/arch/x86/kvm/vmx/posted_intr.c index 3834bb30ce54..259315ea5e44 100644 --- a/arch/x86/kvm/vmx/posted_intr.c +++ b/arch/x86/kvm/vmx/posted_intr.c @@ -42,7 +42,7 @@ static int pi_try_set_control(struct pi_desc *pi_desc, u64 old, u64 new) * update must be retried with a fresh snapshot an ON change causes * the cmpxchg to fail. */ - if (cmpxchg64(&pi_desc->control, old, new) != old) + if (!try_cmpxchg64(&pi_desc->control, &old, new)) return -EBUSY; return 0;