From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-wr1-f54.google.com (mail-wr1-f54.google.com [209.85.221.54]) (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 3AD742F83B7 for ; Wed, 18 Feb 2026 11:00:56 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.221.54 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1771412457; cv=none; b=DbWLED4LDtD2Xw9vh/RPXei/KI1MkkK4epnCUw7GJ1hm2l47jKdW8FGl8WY4o4Io0mOXb0rmiQipqTthgwsrZUHcbijrduTA0OBZ9D5u8f/aAv5WYEeHhCOy85ZCEKC3p5bxi3mWzOYj+R0zLOgVHf3oz2fBto3ALlvHJkZ5bgc= 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=209.85.221.54 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-wr1-f54.google.com with SMTP id ffacd0b85a97d-436317c80f7so480031f8f.1 for ; Wed, 18 Feb 2026 03:00:56 -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=ncC/kPZzPMOBcGMbjtM0EM2E08v9B12sQy25/vPwlUDfqGYyeD+VZgX01RzkXGCCuL 9OoofkeYxlVR24HcSPM7hbUO/HdOMFivazcU9swaOd6/TK9nP4+THZW/t1DbdEmhrYTq iH3P9sUSnTa0sD1l6NGnVoMKqKoENCi8jimWRrx9xCUMfoDkDuOmKebMJedvQXfnPTmj PwLTnuldQy562+QZcmSwqGzPlbT4+rmzYgxxe5icTNKdM84DYSck7Glwp64R75HAb0Z7 eZGauX7LzyxffETJQ+J5c1PM3c4Z/f4/ju7YfFRyXtZRgbd6QatTNZisS5b9adyVX2o3 Wqdw== X-Gm-Message-State: AOJu0Yz+CbA862ICKiOp6+bU7/nl4jd4/6vFirnGnUmk9nKqrK35wiYX oasUByNQpt4N1vs9ou84QHLDNVe7whKdnInMseJp1bzAX2UCiLmozMci33rDJjaD X-Gm-Gg: AZuq6aKv/VwvP/fLLw6dd4bwkmEfzr9yw+SDZM8ionchooQb7tXVDlKJrPQTk1QuSe2 3GB3ZObOQ78ek1UKREoItxPNBi1hlfZoauD3wayNbydVku3s5I7eaPM5DFizLI6RF0pjKhKdf3i +smXdTOaZltku6qrpEzkiZNmGGyH6U9PQbFrxSvwrG8lLDgN7qEOU3zFzYWQoLh/IBWXRjSkltY yoBMdyYqQf7w47ObsWMHrhTSPmfTFcmeE0dMhPwo4+FaAA5V9uD65ytDbJ5jNKdZEsd1/7NcOaZ oVnYoxc41UzPBXPnluys1xjLIlneQvpfriF79MH2TNZKY0WJ5HkAKGSGovDAMx0FQUAXqnftfo9 T1I2LwdnVFC2Uiu4zeMq9dL7/CVwe98tLFrZF/FspUFiY9eZ5LbO3tsQxRlEIpqFl+X0WeMJ/OA RbfuzZQVC4CRNBQ0QIUW0qoeAD44gFffQJmm5VcZAjXABhYsNKBiNf2lvCuBwD49lfMOjTYf/cK 8YHImYBDDQRAxRC3QRx5vLQHAJQkZMw/lhr31tiFr1o 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-hyperv@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Use !try_cmpxchg() instead of cmpxchg (*ptr, old, new) != 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) != old_msg_type) + if (!try_cmpxchg(&msg->header.message_type, + &old_msg_type, HVMSG_NONE)) return; /* 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 *vp, u32 vector) new_iv.vector[new_iv.vector_count++] = vector; - if (cmpxchg(&vp->vp_register_page->interrupt_vectors.as_uint64, - iv.as_uint64, new_iv.as_uint64) != iv.as_uint64) + if (!try_cmpxchg(&vp->vp_register_page->interrupt_vectors.as_uint64, + &iv.as_uint64, new_iv.as_uint64)) return -EAGAIN; return 0; -- 2.53.0