From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stefano Stabellini Subject: Re: [PATCH v2 01/16] Xen: ACPI: Hide UART used by Xen Date: Mon, 18 Jan 2016 11:38:08 +0000 Message-ID: References: <1452840929-19612-1-git-send-email-zhaoshenglong@huawei.com> <1452840929-19612-2-git-send-email-zhaoshenglong@huawei.com> <20160118103216.GB21067@leverpostej> Mime-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Return-path: In-Reply-To: <20160118103216.GB21067@leverpostej> Sender: linux-efi-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Mark Rutland Cc: Shannon Zhao , leif.lindholm-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org, linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org, ard.biesheuvel-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org, stefano.stabellini-Sxgqhf6Nn4DQT0dZR+AlfA@public.gmane.org, david.vrabel-Sxgqhf6Nn4DQT0dZR+AlfA@public.gmane.org, catalin.marinas-5wv7dgnIgG8@public.gmane.org, will.deacon-5wv7dgnIgG8@public.gmane.org, julien.grall-Sxgqhf6Nn4DQT0dZR+AlfA@public.gmane.org, xen-devel-GuqFBffKawuEi8DpZVb4nw@public.gmane.org, devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-efi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, shannon.zhao-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org, peter.huangpeng-hv44wF8Li93QT0dZR+AlfA@public.gmane.org, "Rafael J. Wysocki" , Len Brown , "open list:ACPI" List-Id: linux-efi@vger.kernel.org On Mon, 18 Jan 2016, Mark Rutland wrote: > On Fri, Jan 15, 2016 at 02:55:14PM +0800, 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 > > --- > > CC: "Rafael J. Wysocki" (supporter:ACPI) > > CC: Len Brown (supporter:ACPI) > > CC: linux-acpi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org (open list:ACPI) > > --- > > drivers/acpi/bus.c | 30 ++++++++++++++++++++++++++++++ > > 1 file changed, 30 insertions(+) > > > > diff --git a/drivers/acpi/bus.c b/drivers/acpi/bus.c > > index a212cef..d7a559f 100644 > > --- a/drivers/acpi/bus.c > > +++ b/drivers/acpi/bus.c > > @@ -46,6 +46,7 @@ ACPI_MODULE_NAME("bus"); > > struct acpi_device *acpi_root; > > struct proc_dir_entry *acpi_root_dir; > > EXPORT_SYMBOL(acpi_root_dir); > > +static u64 spcr_uart_addr; > > > > #ifdef CONFIG_X86 > > #ifdef CONFIG_ACPI_CUSTOM_DSDT > > @@ -93,6 +94,17 @@ acpi_status acpi_bus_get_status_handle(acpi_handle handle, > > { > > acpi_status status; > > > > + if (spcr_uart_addr != 0xffffffffffffffff) { > > The SPCR spec says that the Base Address fields being zero means that > console redirection is disabled (though I'm not clear on whether or not > that requires the whole acpi_generic_address to be zero). > > Can we not use that here? Shannon changed the code from 0 to 0xffffffffffffffff following my suggestion to his previous series, but I didn't realize that the SPCR spec says 0 means no console redirection. In that case using 0 is better.