The actual bug is showing in https://gitlab.freedesktop.org/drm/i915/kernel/-/issues/14598 if CONFIG_INTEL_IOMMU_DEFAULT_ON=y , that IOMMU prevent the invalid access, but if CONFIG_INTEL_IOMMU_DEFAULT_ON=n, the invalid access will directly cause system crash after kexec reboot.
-----Original Message----- From: Ville Syrjälä <[email protected]> Sent: Wednesday, October 8, 2025 5:22 AM To: Yao, Jia <[email protected]> Cc: [email protected]; Zuo, Alex <[email protected]>; Lin, Shuicheng <[email protected]>; Askar Safin <[email protected]>; Pingfan Liu <[email protected]>; Chris Wilson <[email protected]> Subject: Re: [PATCH v2] drm/i915: Setting/clearing the memory access bit when en/disabling i915 On Tue, Oct 07, 2025 at 09:40:45PM +0000, Yao, Jia wrote: > You mean intel_pxp_fini(i915) ? > This is because mei_me_shutdown is called after i915_driver_shutdown > in pci_device_shutdown sequence. If we don't close pxp in advance, it > will cause > > [ 295.584775] i915 0000:00:02.0: [drm] *ERROR* gt: MMIO unreliable > (forcewake register returns 0xFFFFFFFF)! So that is the actual bug you're trying to fix? Please just submit the pxp fix on its own. > > Since we disabled PCI_COMMAND_MEMORY in i915_driver_shutdown > > Thanks, > Jia > > -----Original Message----- > From: Ville Syrjälä <[email protected]> > Sent: Tuesday, October 7, 2025 2:25 PM > To: Yao, Jia <[email protected]> > Cc: [email protected]; Zuo, Alex <[email protected]>; > Lin, Shuicheng <[email protected]>; Askar Safin > <[email protected]>; Pingfan Liu <[email protected]>; Chris Wilson > <[email protected]> > Subject: Re: [PATCH v2] drm/i915: Setting/clearing the memory access > bit when en/disabling i915 > > On Tue, Oct 07, 2025 at 08:25:14PM +0000, Jia Yao wrote: > > Make i915's PCI device management more robust by always > > setting/clearing the memory access bit when enabling/disabling the > > device, and by consolidating this logic into helper functions. > > > > It fixes kexec reboot issue by disabling memory access before > > shutting down the device, which can block unsafe and unwanted access from > > DMA. > > > > v2: > > - follow brace style > > > > Link: https://gitlab.freedesktop.org/drm/i915/kernel/-/issues/14598 > > Cc: Alex Zuo <[email protected]> > > Cc: Shuicheng Lin <[email protected]> > > Cc: Askar Safin <[email protected]> > > Cc: Pingfan Liu <[email protected]> > > Suggested-by: Chris Wilson <[email protected]> > > Signed-off-by: Jia Yao <[email protected]> > > --- > > drivers/gpu/drm/i915/i915_driver.c | 35 > > +++++++++++++++++++++++++++--- > > 1 file changed, 32 insertions(+), 3 deletions(-) > > > > diff --git a/drivers/gpu/drm/i915/i915_driver.c > > b/drivers/gpu/drm/i915/i915_driver.c > > index b46cb54ef5dc..766f85726b67 100644 > > --- a/drivers/gpu/drm/i915/i915_driver.c > > +++ b/drivers/gpu/drm/i915/i915_driver.c > > @@ -118,6 +118,33 @@ > > > > static const struct drm_driver i915_drm_driver; > > > > +static int i915_enable_device(struct pci_dev *pdev) { > > + u32 cmd; > > + int ret; > > + > > + ret = pci_enable_device(pdev); > > + if (ret) > > + return ret; > > + > > + pci_read_config_dword(pdev, PCI_COMMAND, &cmd); > > + if (!(cmd & PCI_COMMAND_MEMORY)) > > + pci_write_config_dword(pdev, PCI_COMMAND, cmd | > > +PCI_COMMAND_MEMORY); > > + > > + return 0; > > +} > > NAK. If the pci code is broken then fix the problem there. > Do not add ugly hacks into random drivers. > > > + > > +static void i915_disable_device(struct pci_dev *pdev) { > > + u32 cmd; > > + > > + pci_read_config_dword(pdev, PCI_COMMAND, &cmd); > > + if (cmd & PCI_COMMAND_MEMORY) > > + pci_write_config_dword(pdev, PCI_COMMAND, cmd & > > +~PCI_COMMAND_MEMORY); > > + > > + pci_disable_device(pdev); > > +} > > + > > static int i915_workqueues_init(struct drm_i915_private *dev_priv) { > > /* > > @@ -788,7 +815,7 @@ int i915_driver_probe(struct pci_dev *pdev, const > > struct pci_device_id *ent) > > struct intel_display *display; > > int ret; > > > > - ret = pci_enable_device(pdev); > > + ret = i915_enable_device(pdev); > > if (ret) { > > pr_err("Failed to enable graphics device: %pe\n", ERR_PTR(ret)); > > return ret; > > @@ -796,7 +823,7 @@ int i915_driver_probe(struct pci_dev *pdev, > > const struct pci_device_id *ent) > > > > i915 = i915_driver_create(pdev, ent); > > if (IS_ERR(i915)) { > > - pci_disable_device(pdev); > > + i915_disable_device(pdev); > > return PTR_ERR(i915); > > } > > > > @@ -885,7 +912,7 @@ int i915_driver_probe(struct pci_dev *pdev, const > > struct pci_device_id *ent) > > enable_rpm_wakeref_asserts(&i915->runtime_pm); > > i915_driver_late_release(i915); > > out_pci_disable: > > - pci_disable_device(pdev); > > + i915_disable_device(pdev); > > i915_probe_error(i915, "Device initialization failed (%d)\n", ret); > > return ret; > > } > > @@ -1003,6 +1030,7 @@ void i915_driver_shutdown(struct > > drm_i915_private *i915) > > > > intel_dmc_suspend(display); > > > > + intel_pxp_fini(i915); > > What is that doing in this patch? > > > i915_gem_suspend(i915); > > > > /* > > @@ -1020,6 +1048,7 @@ void i915_driver_shutdown(struct drm_i915_private > > *i915) > > enable_rpm_wakeref_asserts(&i915->runtime_pm); > > > > intel_runtime_pm_driver_last_release(&i915->runtime_pm); > > + i915_disable_device(to_pci_dev(i915->drm.dev)); > > } > > > > static bool suspend_to_idle(struct drm_i915_private *dev_priv) > > -- > > 2.34.1 > > -- > Ville Syrjälä > Intel -- Ville Syrjälä Intel
