From nobody Sun Apr 5 17:27:14 2026 Received: from mail-wm1-f47.google.com (mail-wm1-f47.google.com [209.85.128.47]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E631029E110 for ; Wed, 18 Feb 2026 11:00:55 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.128.47 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1771412457; cv=none; b=RiMH/R2JWdBs0gHUGrwEvSxorsKbh4yoNyU9ZncluyMViaQ+5C1rvGW+prOsD+gAmMrN4g+kDAILfNh4fZag4PHlRlNUWEwsSOvVn/U1FDzIEz7RSfzokYPE36Q3ZKlQKeH+YJw4Ao1udIcrzUG/ElaMVjg3KyUkiXi1OJKvZt8= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1771412457; c=relaxed/simple; bh=jut32K0qD5zIBVpRTNRvCDkT9o6H9Ok5g7HL5cpHO9Y=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=EZUI3S1wQikIqTC6XjW6JKP6BIq/Y/mq2kCocEOqG5P/yMhsIl1HEPAKWU7ZouRGy+D/eK7sKl0AEY/loNRf+XXJ6SiQItjCL6rcXuNtc8m/Ooj4WO0VzuXG3PQEpn8vhH27JbOUWLPNHscK5EPCsNiCTCejRpnOrloxURAzOcY= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=mFNdk2JA; arc=none smtp.client-ip=209.85.128.47 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="mFNdk2JA" Received: by mail-wm1-f47.google.com with SMTP id 5b1f17b1804b1-4806bf39419so5171775e9.1 for ; Wed, 18 Feb 2026 03:00:55 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1771412454; x=1772017254; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=qthjmaZatp2uaj2R40wSdI4uEfUCjCNWJ8jI4UcjTZM=; b=mFNdk2JAUyWNjqFDJ04UbR48jtVHACrlNROeDzS8/XiyOSt6BwamqqlVno6JZ0Kq6c RVn45/ZNlHwjYAso64XVwtjXpPTX8hqqUP4Pa13kl51TMc09gsAq9VEpYdp4WciOU7Zu 0sk0Q7ZuL/iERODCQ+s8y/oQluvIAzJGxS3D5EZr3f/OtdVZ9uNzdEE/zJizojhQ9U2V LL3ke8CQxEKjDk54j/dp9GTHvbEKdRA4yFArXEVvHCmcfKTMl2FGy1WLtSXquuH31cMM TBE4CfRBNu1oE8IvUAsZ7aAIIGjvgHQ2gfuzX6XdFDR88A8+s77Nj70TQzjGoIRBpePR APNA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1771412454; x=1772017254; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-gg:x-gm-message-state:from :to:cc:subject:date:message-id:reply-to; bh=qthjmaZatp2uaj2R40wSdI4uEfUCjCNWJ8jI4UcjTZM=; b=b8mPUE1vdLaMOi6qdQEvFIYCRQ0xXHcdmZiebcGcrES9iM9jyK/WFowrPc4aWaK/ZZ NAECi0I7ff1tXdZcHNQ5s9wtRGY3BAdanJCoXFrgXGA33TSQ+4PUb43Jx9dK8wmIFJO/ TBoSSsKbskJJAk+q4fH1ZIgpF9qeAT8cGQk+xuwi8WEkp+pdjXCLjVWOxY7atQOO09bi KP8cpykoIZIawlpjp2Kr40+N6dIJAl1KIZI63z88WD5k6I045FlCVNs1IupLGIaLFOC7 NQyUV4c8mX+mPFG3OIsiLvlHE04OGeMMb2PmKFbtdZ6pHPyyVq7Wu+h5Jfq921j/u4qX uE7g== X-Forwarded-Encrypted: i=1; AJvYcCVQrotEKxbAtOic647lyrTEL0zCjNvqgWlo1yACkSQ0dawurrf7SmEiCuKYu0odgKDAK0j+itJxBWwRmXI=@vger.kernel.org X-Gm-Message-State: AOJu0Yw3akcK7jIQvafeQBgNBkmTIdqrqIPu0OVbIeLxX0JFcJ1nHfHU EEMEzV7XPCKXWOte7Yxr/n7+PYv06JjwVgtgwbnv2fB6TjjBMOTalAyi X-Gm-Gg: AZuq6aKwKtJtZ9lR6MFd7iMbFEfUAbRhJHCmKHtR75khewlboEIxkyAGF+8OuJmqJ2Q U9YqbBQvA04n9zmKnAlKp5JdsSWjINSHSlyUVzSPKVKVfG4hAY3nVIy5K33DFFO5yMuluEPONk6 /WsnV6NAdx5yDXA8DntTXmHYYDKthzScfXZaDcvTrofF5vPkD3oy88pPlCEKQSWxwtu887Xat+t P1UVbW+ccVfrEqSIgfgkzlj/IwgQCFIAKoHH+G50zVAp4pcaiWIlR5JmBHdr4PHVV7NOYgt4tgx o7Ra1uNWUL4x6EPSzsIKZG21gtChFvkEw9J8G9hhVNMVuPdPjwCrZNGpJjMPDeplyRp9DuiUqvc GddhTiOq+L6zqXmDgoxjOmUdRiSw7DFECraGTni9w+GQC1Kx3Bb10XuoNhco3XQ2oWtBcvPHNeM RJaKY1ZF0oSfn4o+BG6m2NtxWCJrmpJRVieAXwiCo6O4ef/2q2BjJ1OSkmGFwyoiQv9gg9XkV/Z DL5dL6TH6AJArEc3Avsvj4UmS+qWuN/KlxXD3at9ZIf X-Received: by 2002:a05:600c:c1c8:20b0:47e:e0b3:2437 with SMTP id 5b1f17b1804b1-48398c667edmr17184675e9.5.1771412453875; Wed, 18 Feb 2026 03:00:53 -0800 (PST) Received: from fedora ([193.77.86.199]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4839712580esm26652285e9.1.2026.02.18.03.00.52 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 18 Feb 2026 03:00:53 -0800 (PST) From: Uros Bizjak To: linux-hyperv@vger.kernel.org, linux-kernel@vger.kernel.org Cc: Uros Bizjak , "K. Y. Srinivasan" , Haiyang Zhang , Wei Liu , Dexuan Cui , Long Li Subject: [PATCH RESEND] mshv: Use try_cmpxchg() instead of cmpxchg() Date: Wed, 18 Feb 2026 12:00:18 +0100 Message-ID: <20260218110041.179949-1-ubizjak@gmail.com> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260218102604.178561-1-ubizjak@gmail.com> References: <20260218102604.178561-1-ubizjak@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Use !try_cmpxchg() instead of cmpxchg (*ptr, old, new) !=3D old. x86 CMPXCHG instruction returns success in ZF flag, so this change saves a compare after CMPXCHG. The generated assembly code improves from e.g.: 415: 48 8b 44 24 30 mov 0x30(%rsp),%rax 41a: 48 8b 54 24 38 mov 0x38(%rsp),%rdx 41f: f0 49 0f b1 91 a8 02 lock cmpxchg %rdx,0x2a8(%r9) 426: 00 00 428: 48 3b 44 24 30 cmp 0x30(%rsp),%rax 42d: 0f 84 09 ff ff ff je 33c <...> to: 415: 48 8b 44 24 30 mov 0x30(%rsp),%rax 41a: 48 8b 54 24 38 mov 0x38(%rsp),%rdx 41f: f0 49 0f b1 91 a8 02 lock cmpxchg %rdx,0x2a8(%r9) 426: 00 00 428: 0f 84 0e ff ff ff je 33c <...> No functional change intended. Signed-off-by: Uros Bizjak Cc: "K. Y. Srinivasan" Cc: Haiyang Zhang Cc: Wei Liu Cc: Dexuan Cui Cc: Long Li --- drivers/hv/hyperv_vmbus.h | 4 ++-- drivers/hv/mshv_eventfd.c | 4 ++-- 2 files changed, 4 insertions(+), 4 deletions(-) diff --git a/drivers/hv/hyperv_vmbus.h b/drivers/hv/hyperv_vmbus.h index cdbc5f5c3215..7bd8f8486e85 100644 --- a/drivers/hv/hyperv_vmbus.h +++ b/drivers/hv/hyperv_vmbus.h @@ -370,8 +370,8 @@ static inline void vmbus_signal_eom(struct hv_message *= msg, u32 old_msg_type) * CHANNELMSG_UNLOAD_RESPONSE and we don't care about other messages * on crash. */ - if (cmpxchg(&msg->header.message_type, old_msg_type, - HVMSG_NONE) !=3D old_msg_type) + if (!try_cmpxchg(&msg->header.message_type, + &old_msg_type, HVMSG_NONE)) return; =20 /* diff --git a/drivers/hv/mshv_eventfd.c b/drivers/hv/mshv_eventfd.c index 0b75ff1edb73..525e002758e4 100644 --- a/drivers/hv/mshv_eventfd.c +++ b/drivers/hv/mshv_eventfd.c @@ -128,8 +128,8 @@ static int mshv_vp_irq_try_set_vector(struct mshv_vp *v= p, u32 vector) =20 new_iv.vector[new_iv.vector_count++] =3D vector; =20 - if (cmpxchg(&vp->vp_register_page->interrupt_vectors.as_uint64, - iv.as_uint64, new_iv.as_uint64) !=3D iv.as_uint64) + if (!try_cmpxchg(&vp->vp_register_page->interrupt_vectors.as_uint64, + &iv.as_uint64, new_iv.as_uint64)) return -EAGAIN; =20 return 0; --=20 2.53.0