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[109.243.148.111]) by smtp.gmail.com with ESMTPSA id 2adb3069b0e04-5ad69580f7fsm5934492e87.61.2026.06.29.06.49.42 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 29 Jun 2026 06:49:42 -0700 (PDT) X-BeenThere: xen-devel@lists.xenproject.org List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xenproject.org Precedence: list Sender: "Xen-devel" Authentication-Results: eu.smtp.expurgate.cloud; dkim=pass header.s=20251104 header.d=gmail.com header.i="@gmail.com" header.h="Content-Transfer-Encoding:In-Reply-To:From:Content-Language:References:Cc:To:Subject:User-Agent:MIME-Version:Date:Message-ID" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1782740983; x=1783345783; darn=lists.xenproject.org; h=content-transfer-encoding:in-reply-to:from:content-language :references:cc:to:subject:user-agent:mime-version:date:message-id :from:to:cc:subject:date:message-id:reply-to; bh=495slxjqKmCy38FTYb4GpyK5CV8lVyW69ubl9euwJ/E=; b=S53NKLazZfwiCYb2mJ/WSwlY6AY5/8Le5jLMgsyyNO+m+pscKSdYcPsL2iT7dYuhgM pn6CoojLdecwxEfr2XeDq+Y5btr6ke71/KnIOO2qycAm65K1HtaDRS+M8kNpwykCWezZ XjTTxgbn6eqVZbC2m6N7sr+a23SltISXL9cKoVsYLurxcTPmgQIsNJKNtp1TFuIQZAC9 gPovTBOnp9VFNxkC7r0sqTguE8eAo+jxSqZ8A4h2X94mPn5MrlTwY1elDPWaP32i3nE3 N5lUqnvJvvQhTzNGNH6xK50a+VdQCdYL2TCBF618fLvGbO/mkS2GiloGTQUaOMM7Lv4x axow== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1782740983; x=1783345783; h=content-transfer-encoding:in-reply-to:from:content-language :references:cc:to:subject:user-agent:mime-version:date:message-id :x-gm-gg:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=495slxjqKmCy38FTYb4GpyK5CV8lVyW69ubl9euwJ/E=; b=fcbUznjbhK9qRQ9E6RI89j0inOknSDSxerdGuOO4u0M9u0FGGpoCZ0q5aNZ3PXpZYz KLOCE8ve1oUBpfnI1cnzZyLBYrm7JClKAIPtP4FEGRDQjtLSclabrY47S2WjGmSv97en bsMeizja79AFNaBTSJL/n+79J/F2GuTTv9goNjrMzuquXClS7FkuEs5+23V3GcX6HWJ4 Nq4s/RtNoTiszoHmB5SMXYlg7S6iTMUpR/25LyYD7ygQQ3Q+rcJwqJ+YY52dIRw9YjIF /rbWKPxVvDSOcUoPQp8o/ekkEjRdgXvKK82HIeVMFn2PYJPZE1l5r2va3K372YN6Q3PF CAmQ== X-Forwarded-Encrypted: i=1; AHgh+Rpejy6o4GZCb8lBXDekyipQtELKHRPYk1DYjTS4xq9r479nRHNn+/QeqjpBkK5zkwOrN0D0nApg9nQ=@lists.xenproject.org X-Gm-Message-State: AOJu0Ywi2hpSv/PpQdU5XBsLqml4gqVBd67lXJiJdT/MNVQOis5M9yxC a3h66ICZzxJeiEVmnTuOW7PgRU15xJkYrBxUaRVES1wPBWIwXclYSQYU X-Gm-Gg: AfdE7clLWqdz//BmvdgL9RaZ0OiQcXUd4Wqcvutl8xTYdVnmBF8fBOdtGh6hq1GYi1Y CHiVQRpKjibbgt79SdrZCrf74SY0flmSaZ51l9G8J5vgzxml3c1x6KAYr17na/gJ2tjbFtlWIpF NojaGmN8/yZlGb8UsSGnltXRzREDaSnVG2Ppz1uE8v1Two2we9hqCLLlcXiTpVXZDqCDflXGVox recqjidrTuWzUdhqnqobrhIy+UJw4s6KWUaH3VNcxMX4CKjf/Ph9a2U88UxHwhTjkto34/JJEk0 D5FXGvGz2YhVQT8fpreEVYt1tNfaeGb5Z6Tu8/BJ0zchS1Y/1L+NDmCUDqd3HZwOJm5wQOUVWz2 c1/MNo2A5CKr7tmsCEQ8KAWQBik5ZWAgoTCGV5nuDa4GBrmSNNU70E1VDqtNUZ1BKX2jBKueaAi 0qbgsMwSF9IPKtUcewBqIHM14AgA7TbzqxFoZrOt5Ul+KIDtzpXM7dj6wrANSUFKwKgHM= X-Received: by 2002:a05:6512:6513:b0:5ae:b7d4:7dd7 with SMTP id 2adb3069b0e04-5aeb7d47e82mr875497e87.24.1782740982857; Mon, 29 Jun 2026 06:49:42 -0700 (PDT) Message-ID: Date: Mon, 29 Jun 2026 15:49:41 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH for-4.22 v2 4/4] char/ns16550: bound execution time of ns16550_interrupt() To: Roger Pau Monne , xen-devel@lists.xenproject.org Cc: Andrew Cooper , Anthony PERARD , Michal Orzel , Jan Beulich , Julien Grall , Stefano Stabellini References: <20260629094531.55555-1-roger.pau@citrix.com> <20260629094531.55555-5-roger.pau@citrix.com> Content-Language: en-US From: Oleksii Kurochko In-Reply-To: <20260629094531.55555-5-roger.pau@citrix.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-purgate-ID: tlsNG-c1860d/1782740983-43D333FC-FAAD670B/10/73395122804 X-purgate-type: spam X-purgate-size: 1031 On 6/29/26 11:45 AM, Roger Pau Monne wrote: > The current logic in ns16550_interrupt() will loop until the device sets > the NOINT in IIR. At least on the Lenovo ThinkSystem SR630 V4 the flow > control of the serial-over-lan emulated UART seems to be broken, as it > doesn't set the NOINT bit consistently. The Transmitter Holding Register > Empty in LSR also seems to not be properly signaled, as even with it set > writes to the transmit register take ~6ms. This leads to the watchdog > triggering very easily on such system. > > Introduce an upper bound on the execution time of ns16550_interrupt(), this > is currently set as 4x the polling interval, which is calculated as the > time to fill RX FIFO and/or empty TX FIFO. The current maximum is 5ms. > Once the timeout triggers the interrupt is disabled and the uart is > switched to polling mode. > > Signed-off-by: Roger Pau Monné Release-Acked-by: Oleksii Kurochko Thanks. ~ Oleksii