From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ian Campbell Subject: Re: [PATCH] xen: arm: configure correct dom0_gnttab_start/size Date: Tue, 4 Nov 2014 10:17:29 +0000 Message-ID: <1415096249.11486.12.camel@citrix.com> References: <1410448889-18731-1-git-send-email-ian.campbell@citrix.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1410448889-18731-1-git-send-email-ian.campbell@citrix.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: xen-devel@lists.xen.org, Konrad Rzeszutek Wilk Cc: julien.grall@linaro.org, tim@xen.org, stefano.stabellini@eu.citrix.com List-Id: xen-devel@lists.xenproject.org On Thu, 2014-09-11 at 16:21 +0100, Ian Campbell wrote: I think we should apply this workaround for 4.5 and do things properly for 4.6. Any thoughts? > Vexpress is currently failing to boot for me with: > ------------[ cut here ]------------ > WARNING: CPU: 0 PID: 1 at arch/arm/mm/ioremap.c:301 __arm_ioremap_pfn_caller+0x118/0x1a4() > CPU: 0 PID: 1 Comm: swapper Tainted: G W 3.16.0-arm-native+ #276 > [] (unwind_backtrace) from [] (show_stack+0x10/0x14) > [] (show_stack) from [] (warn_slowpath_common+0x5c/0x7c) > [] (warn_slowpath_common) from [] (warn_slowpath_null+0x18/0x20) > [] (warn_slowpath_null) from [] (__arm_ioremap_pfn_caller+0x118/0x1a4) > [] (__arm_ioremap_pfn_caller) from [] (__arm_ioremap+0x14/0x20) > [] (__arm_ioremap) from [] (gnttab_setup_auto_xlat_frames+0x30/0xdc) > [] (gnttab_setup_auto_xlat_frames) from [] (xen_guest_init+0x19c/0x2d4) > [] (xen_guest_init) from [] (do_one_initcall+0xfc/0x1a4) > [] (do_one_initcall) from [] (kernel_init_freeable+0x58/0x1b4) > [] (kernel_init_freeable) from [] (kernel_init+0x8/0xe4) > [] (kernel_init) from [] (ret_from_fork+0x14/0x3c) > ---[ end trace 3406ff24bd97382f ]--- > xen:grant_table: Failed to ioremap gnttab share frames (addr=0x00000000b0000000)! > > which is: > /* > * Don't allow RAM to be mapped - this causes problems with ARMv6+ > */ > if (WARN_ON(pfn_valid(pfn))) > return NULL; > > This makes sense since the gnttab defaults to 0xb000000 and my dom0 > is being allocated a 1:1 mapping at 0xa0000000-0xc0000000. > > I suspect this broke around the time we stopped forcing dom0 memory to be > allocated as low as possible which happened to prevent the default dom0_gnttab > region overlapping RAM. > > This patch specifies an explicit dom0_gnttab base which is explicitly unused > according to the FVP model docs (although it correpsonds to CS5 this isn't > wired up to anything). > > Signed-off-by: Ian Campbell > --- > This just fixes vexpress, I wonder if a followup patch should either remove the > default dom0_gnttab (forcing all platforms to specify one explicitly) or make > the default something less arbitrary than 0xb0000000, e.g. 0x0-0x20000 or > 0xfffe0000-0x100000000 (very start or very end of RAM). Perhaps with a command > line option to override for new platform hacking. > > Or maybe we should search for an unused hole in the dom0 RAM space? > --- > xen/arch/arm/platforms/vexpress.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/xen/arch/arm/platforms/vexpress.c b/xen/arch/arm/platforms/vexpress.c > index 8e6a4ea..ce66935 100644 > --- a/xen/arch/arm/platforms/vexpress.c > +++ b/xen/arch/arm/platforms/vexpress.c > @@ -176,6 +176,8 @@ PLATFORM_START(vexpress, "VERSATILE EXPRESS") > #endif > .reset = vexpress_reset, > .blacklist_dev = vexpress_blacklist_dev, > + .dom0_gnttab_start = 0x10000000, > + .dom0_gnttab_size = 0x20000, > PLATFORM_END > > /*