From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 6A4C44DA53C for ; Wed, 22 Jul 2026 11:28:35 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.129.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784719722; cv=none; b=chTKWd8oS/Eo9IuM0kK64rbtPYTKBex8LQibGrJzj77p0RP5ejzj79w0BnNRZ2aMP+PhK2TrgOXIGuXtit7amugnFd8titzT4B6iNEuPzf1vfdAvkb58uszkx3HBQx9I4tpZWWf4CYLS5AUEq/FeQeyAIn6LVNr3k/Pg96uzmXs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784719722; c=relaxed/simple; bh=hOkzl25QMkR31KWjR8NOxhwtgyg0bzm7KtlMeuS5bG4=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:content-type; b=SYL9PJitpW6r0Gas7ywciie6ZzcGOaN9wacUjzcsqqwa+odbFVwfJivjaRkcJ+6W+au8ERRAhpOLRuXvgl1Ts9HM5AfqI22REK8VfNBRohnZpZkgOoBduMAdTaEsTUh2vrpfgnJ77JN2cw8D6VUbFv4/tyxm49VnaXb+4CsZhd0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=UZOUOVhD; arc=none smtp.client-ip=170.10.129.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="UZOUOVhD" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1784719710; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=hOkzl25QMkR31KWjR8NOxhwtgyg0bzm7KtlMeuS5bG4=; b=UZOUOVhDHwILaO7WdiMTDM/qCPfcVtRwfFMDWqhO0RTJVIPork6JLqrH2amQMWPo1PqMjQ iSqKcQEmKBr91wlOe7VveLPjRgswy/rWB0cdpfQlhpcN7vGSYW2ibaE0+wvZDAOMjMIrGl aN/tG4J1Jwyl60TJncUjQ5BOUI++bxI= Received: from mx-prod-mc-03.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-623-Uzggo0ZANlGaYbji_F0fhQ-1; Wed, 22 Jul 2026 07:28:23 -0400 X-MC-Unique: Uzggo0ZANlGaYbji_F0fhQ-1 X-Mimecast-MFC-AGG-ID: Uzggo0ZANlGaYbji_F0fhQ_1784719701 Received: from mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.17]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id BA896191DFEB; Wed, 22 Jul 2026 11:28:20 +0000 (UTC) Received: from fedora.redhat.com (unknown [10.44.48.27]) by mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id C8B96195423C; Wed, 22 Jul 2026 11:28:14 +0000 (UTC) From: Jose Ignacio Tornos Martinez To: bhelgaas@google.com, alex@shazbot.org, mani@kernel.org Cc: jtornosm@redhat.com, sashiko-bot@kernel.org, sashiko-reviews@lists.linux.dev, jjohnson@kernel.org, linux-pci@vger.kernel.org, linux-wireless@vger.kernel.org, ath11k@lists.infradead.org, ath12k@lists.infradead.org, mhi@lists.linux.dev, linux-kernel@vger.kernel.org Subject: Re: [PATCH v13] PCI: Add device-specific reset for Qualcomm devices Date: Wed, 22 Jul 2026 13:28:13 +0200 Message-ID: <20260722112813.33153-1-jtornosm@redhat.com> In-Reply-To: <20260721082933.7B5A41F000E9@smtp.kernel.org> References: <20260721082933.7B5A41F000E9@smtp.kernel.org> Precedence: bulk X-Mailing-List: mhi@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.0 on 10.30.177.17 X-Mimecast-MFC-PROC-ID: W8BTILu5XAQdI71LKaUvVo835NGHhWy7ZBpMyTRGRqY_1784719701 X-Mimecast-Originator: redhat.com Content-Transfer-Encoding: 8bit content-type: text/plain; charset="US-ASCII"; x-default=true > [Severity: High] > Will this sequence of ioread32 flush reads and > read_poll_timeout trigger Master Aborts on architectures > with strict error handling? > > The SoC global reset explicitly drops the device PCIe link. > Performing ioread32 flush reads immediately after asserting > the reset, and then actively polling the disconnected MMIO > space with read_poll_timeout while the link recovers, can > result in Unsupported Request errors. > > On strict platforms like ARM64 or x86 servers with APEI/GHES > Firmware First error handling, these can escalate to fatal > Uncorrectable Errors and cause a host kernel panic when a > guest VM exits. > > Should this avoid MMIO flush reads during these reset > sequences and instead use fixed delays to safely bridge the > link-down period? The SoC global reset at 0x3008 does not immediately drop the PCIe link. The flush reads execute while the device is still responsive - the actual reset takes effect during the subsequent msleep. The ath11k/ath12k drivers perform the same register accesses during this reset sequence, including on ARM64 Qualcomm platforms, without issues. The read_poll_timeout polling for link recovery follows the same pattern used elsewhere in the PCI subsystem for waiting on device responses after reset. Tested over 100+ VM crash/reset cycles on x86 with VFIO passthrough without errors. > [Severity: High] > Could this immediate ioread32 flush read also trigger a > fatal Master Abort if the link drops instantly after writing > the MHI SoC reset request? Same as above - the MHI SoC reset does not instantly drop the PCIe link. The flush read completes before the reset takes effect, and the 2-second delay covers the actual reset period. This replicates the MHI driver behavior (mhi_pci_reset_prepare()).