From patchwork Tue Feb 9 11:19:02 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Stefano Stabellini X-Patchwork-Id: 8260161 Return-Path: X-Original-To: patchwork-linux-arm@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork2.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.136]) by patchwork2.web.kernel.org (Postfix) with ESMTP id 5C80EBEEE5 for ; Tue, 9 Feb 2016 11:21:21 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 64AF82025A for ; Tue, 9 Feb 2016 11:21:20 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.9]) (using TLSv1.2 with cipher AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 732D220254 for ; Tue, 9 Feb 2016 11:21:19 +0000 (UTC) Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.80.1 #2 (Red Hat Linux)) id 1aT6Kk-0006Y2-Fm; Tue, 09 Feb 2016 11:19:50 +0000 Received: from smtp.citrix.com ([66.165.176.89]) by bombadil.infradead.org with esmtps (Exim 4.80.1 #2 (Red Hat Linux)) id 1aT6Kh-0006VA-Kv for linux-arm-kernel@lists.infradead.org; Tue, 09 Feb 2016 11:19:48 +0000 X-IronPort-AV: E=Sophos;i="5.22,420,1449532800"; d="scan'208";a="330530225" Date: Tue, 9 Feb 2016 11:19:02 +0000 From: Stefano Stabellini X-X-Sender: sstabellini@kaball.uk.xensource.com To: "Rafael J. Wysocki" Subject: Re: [PATCH v4 01/17] Xen: ACPI: Hide UART used by Xen In-Reply-To: <2213954.ztOe55fprN@vostro.rjw.lan> Message-ID: References: <1454641552-12576-1-git-send-email-zhaoshenglong@huawei.com> <2213954.ztOe55fprN@vostro.rjw.lan> User-Agent: Alpine 2.02 (DEB 1266 2009-07-14) MIME-Version: 1.0 X-DLP: MIA2 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20160209_031947_886384_23539C54 X-CRM114-Status: GOOD ( 22.80 ) X-Spam-Score: -7.2 (-------) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.20 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Mark Rutland , "devicetree@vger.kernel.org" , linux-efi@vger.kernel.org, Catalin Marinas , ian.campbell@citrix.com, ard.biesheuvel@linaro.org, Stefano Stabellini , "Rafael J. Wysocki" , Will Deacon , Linux Kernel Mailing List , xen-devel@lists.xen.org, julien.grall@citrix.com, "open list:ACPI" , stefano.stabellini@citrix.com, david.vrabel@citrix.com, Shannon Zhao , peter.huangpeng@huawei.com, Len Brown , "linux-arm-kernel@lists.infradead.org" , Shannon Zhao Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org X-Spam-Status: No, score=-4.5 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_MED, RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP On Mon, 8 Feb 2016, Rafael J. Wysocki wrote: > On Monday, February 08, 2016 10:57:01 AM Stefano Stabellini wrote: > > On Sat, 6 Feb 2016, Rafael J. Wysocki wrote: > > > On Fri, Feb 5, 2016 at 4:05 AM, Shannon Zhao wrote: > > > > From: Shannon Zhao > > > > > > > > ACPI 6.0 introduces a new table STAO to list the devices which are used > > > > by Xen and can't be used by Dom0. On Xen virtual platforms, the physical > > > > UART is used by Xen. So here it hides UART from Dom0. > > > > > > > > Signed-off-by: Shannon Zhao > > > > Reviewed-by: Stefano Stabellini > > > > > > Well, this doesn't look right to me. > > > > > > We need to find a nicer way to achieve what you want. > > > > I take that you are talking about how to honor the STAO table in Linux. > > Do you have any concrete suggestions? > > I do. > > The last hunk of the patch is likely what it needs to be, although I'm > not sure if the place it is added to is the right one. That's a minor thing, > though. > > The other part is problematic. Not that as it doesn't work, but because of > how it works. With these changes the device will be visible to the OS (in > fact to user space even), but will never be "present". I'm not sure if > that's what you want? > > It might be better to add a check to acpi_bus_type_and_status() that will > evaluate the "should ignore?" thing and return -ENODEV if this is true. This > way the device won't be visible at all. Something like below? Actually your suggestion is better, thank you! diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c index 78d5f02..4778c51 100644 --- a/drivers/acpi/scan.c +++ b/drivers/acpi/scan.c @@ -1455,6 +1455,9 @@ static int acpi_bus_type_and_status(acpi_handle handle, int *type, if (ACPI_FAILURE(status)) return -ENODEV; + if (acpi_check_device_is_ignored(handle)) + return -ENODEV; + switch (acpi_type) { case ACPI_TYPE_ANY: /* for ACPI_ROOT_OBJECT */ case ACPI_TYPE_DEVICE: