linux-kernel - Re: [PATCH 6/9] drm/xe: Remove driver side BAR release before resize

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Message-ID: <3ts3e2fwom7inbu2kzrvljo5mm7wz5ruaf6daib6cf5tk3v4al@njzufk22tcsy>
Date: Tue, 28 Oct 2025 16:24:04 -0500
From: Lucas De Marchi <lucas.demarchi@...el.com>
To: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
CC: Alex Bennée <alex.bennee@...aro.org>, Simon Richter
	<Simon.Richter@...yros.de>, Alex Deucher <alexander.deucher@....com>,
	<amd-gfx@...ts.freedesktop.org>, Bjorn Helgaas <bhelgaas@...gle.com>, "David
 Airlie" <airlied@...il.com>, <dri-devel@...ts.freedesktop.org>,
	<intel-gfx@...ts.freedesktop.org>, <intel-xe@...ts.freedesktop.org>, "Jani
 Nikula" <jani.nikula@...ux.intel.com>, Joonas Lahtinen
	<joonas.lahtinen@...ux.intel.com>, <linux-pci@...r.kernel.org>, Rodrigo Vivi
	<rodrigo.vivi@...el.com>, Simona Vetter <simona@...ll.ch>, Tvrtko Ursulin
	<tursulin@...ulin.net>, Christian König
	<christian.koenig@....com>, Thomas Hellström
	<thomas.hellstrom@...ux.intel.com>, Michał Winiarski
	<michal.winiarski@...el.com>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 6/9] drm/xe: Remove driver side BAR release before resize

On Tue, Oct 28, 2025 at 07:35:48PM +0200, Ilpo Järvinen wrote:
>PCI core handles releasing device's resources and their rollback in
>case of failure of a BAR resizing operation. Releasing resource prior
>to calling pci_resize_resource() prevents PCI core from restoring the
>BARs as they were.
>
>Remove driver-side release of BARs from the xe driver.
>
>Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
>Cc: Lucas De Marchi <lucas.demarchi@...el.com>
>---
> drivers/gpu/drm/xe/xe_vram.c | 3 ---
> 1 file changed, 3 deletions(-)
>
>diff --git a/drivers/gpu/drm/xe/xe_vram.c b/drivers/gpu/drm/xe/xe_vram.c
>index b44ebf50fedb..929412f0d131 100644
>--- a/drivers/gpu/drm/xe/xe_vram.c
>+++ b/drivers/gpu/drm/xe/xe_vram.c
>@@ -33,9 +33,6 @@ _resize_bar(struct xe_device *xe, int resno, resource_size_t size)
> 	int bar_size = pci_rebar_bytes_to_size(size);
> 	int ret;
>
>-	if (pci_resource_len(pdev, resno))
>-		pci_release_resource(pdev, resno);
>-

conflict with drm-xe-next:

++<<<<<<< ours
  +      release_bars(pdev);
  +
++=======
++>>>>>>> theirs

if we don't need to release the BARs anymore to call
pci_resize_resource(), then the resolution is simply to drop the
function release_bars() function.

I'm sending that to our CI for coverage:
https://lore.kernel.org/intel-xe/20251028211613.3228940-2-lucas.demarchi@intel.com/T/#u

thanks
Lucas De Marchi

> 	ret = pci_resize_resource(pdev, resno, bar_size);
> 	if (ret) {
> 		drm_info(&xe->drm, "Failed to resize BAR%d to %dM (%pe). Consider enabling 'Resizable BAR' support in your BIOS\n",
>-- 
>2.39.5
>