From mboxrd@z Thu Jan 1 00:00:00 1970 From: Peter Wu Subject: Re: [PATCH] qxl: fix null-pointer crash during suspend Date: Mon, 1 Oct 2018 22:33:22 +0200 Message-ID: <20181001203322.GA13696@al> References: <20180904202747.14968-1-peter@lekensteyn.nl> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org To: Fubo Chen Cc: airlied@redhat.com, kraxel@redhat.com, alan.christopher.jenkins@gmail.com, virtualization@lists.linux-foundation.org, dri-devel@lists.freedesktop.org, Linux Kernel List-Id: dri-devel@lists.freedesktop.org On Mon, Oct 01, 2018 at 01:13:59PM -0700, Fubo Chen wrote: > On Tue, Sep 4, 2018 at 2:10 PM Peter Wu wrote: > > > > "crtc->helper_private" is not initialized by the QXL driver and thus the > > "crtc_funcs->disable" call would crash (resulting in suspend failure). > > Fix this by converting the suspend/resume functions to use the > > drm_mode_config_helper_* helpers. > > > > Tested system sleep with QEMU 3.0 using "echo mem > /sys/power/state". > > During suspend the following message is visible from QEMU: > > > > spice/server/display-channel.c:2425:display_channel_validate_surface: canvas address is 0x7fd05da68308 for 0 (and is NULL) > > spice/server/display-channel.c:2426:display_channel_validate_surface: failed on 0 > > > > This seems to be triggered by QXL_IO_NOTIFY_CMD after > > QXL_IO_DESTROY_PRIMARY_ASYNC, but aside from the warning things still > > seem to work (tested with both the GTK and -spice options). > > > > Signed-off-by: Peter Wu > > Is this a new issue or something that was introduced a long time ago? > In the latter case, please consider adding a "Cc: > " tag to this patch. I am not sure exactly when the issue was introduced, but the original code was added in v3.10-rc7-800-gd84300bf7934 while the new drm_mode_config_helper_suspend API was added in 4.16. The intended call chain to initialize the private object seems to be: drm_crtc_helper_add <- qdev_crtc_init <- qxl_modeset_init <- qxl_pci_probe If any error occurs along the callchain, then the helper_private pointer will remain NULL. Or if the crtc is obtained in a different way (not sure how). Not sure if it is worth backporting, suspend/resume does not seem an important use case for VMs using QXL and the fix was not validated for older kernels. -- Kind regards, Peter Wu https://lekensteyn.nl