Re: [PATCH v2 3/7] PCI: Honor alignment overrides
From: Jani Nikula <jani.nikula@linux.intel.com>
Date: 2026-10-02 11:46:44
Also in:
dri-devel, intel-gfx, linux-alpha, linux-m68k, linux-mips, linux-pci, linux-sh, lkml
On Fri, 02 Oct 2026, Ilpo Järvinen [off-list ref] wrote:
pci=resource_alignment argument can override the default alignment for
the resource. The remainder code introduced in the commit 9036bd0efcb6
("PCI: Align head space better") can move remainder space (non-aligning
part of the size) before the aligning left edge which results in
violating the requested alignment.
Introduce struct pci_resreq_data to hold device and user-given alignment
to be able to honor it in pci_align_resource(). When user-given alignment
is found, any remainder movement is skipped.
Fixes: 9036bd0efcb6 ("PCI: Align head space better")
Reported-by: Sashiko <sashiko-bot@kernel.org>
Link: https://lore.kernel.org/linux-pci/20260923133202.07DF61F000FF@smtp.kernel.org/ (local)
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>So I don't have the time to figure out what's going on here, but assuming you get proper review, the i915 part is Acked-by: Jani Nikula <redacted> for merging via whichever tree makes sense.
quoted hunk ↗ jump to hunk
--- arch/alpha/kernel/pci.c | 3 ++- arch/arm/kernel/bios32.c | 5 +++-- arch/m68k/kernel/pcibios.c | 4 ++-- arch/mips/pci/pci-generic.c | 5 +++-- arch/mips/pci/pci-legacy.c | 5 +++-- arch/parisc/kernel/pci.c | 5 +++-- arch/powerpc/kernel/pci-common.c | 5 +++-- arch/sh/drivers/pci/pci.c | 5 +++-- arch/x86/pci/i386.c | 5 +++-- arch/xtensa/kernel/pci.c | 5 +++-- drivers/char/agp/intel-gtt.c | 5 ++++- drivers/gpu/drm/i915/i915_gmch.c | 5 +++-- drivers/pci/pci.c | 5 +++-- drivers/pci/setup-res.c | 19 +++++++++++++------ include/linux/pci.h | 26 ++++++++++++++++++++++++-- 15 files changed, 75 insertions(+), 32 deletions(-)diff --git a/arch/alpha/kernel/pci.c b/arch/alpha/kernel/pci.c index 11df411b1d18..c5d725a9781f 100644 --- a/arch/alpha/kernel/pci.c +++ b/arch/alpha/kernel/pci.c@@ -128,7 +128,8 @@ pcibios_align_resource(void *data, const struct resource *res, const struct resource *empty_res, resource_size_t size, resource_size_t align) { - struct pci_dev *dev = data; + struct pci_resreq_data *rr = data; + struct pci_dev *dev = rr->dev; struct pci_controller *hose = dev->sysdata; unsigned long alignto; resource_size_t start = res->start;diff --git a/arch/arm/kernel/bios32.c b/arch/arm/kernel/bios32.c index ac0e890510da..3e61826f07fb 100644 --- a/arch/arm/kernel/bios32.c +++ b/arch/arm/kernel/bios32.c@@ -564,7 +564,8 @@ resource_size_t pcibios_align_resource(void *data, const struct resource *res, resource_size_t size, resource_size_t align) { - struct pci_dev *dev = data; + struct pci_resreq_data *rr = data; + struct pci_dev *dev = rr->dev; resource_size_t start = res->start; struct pci_host_bridge *host_bridge;@@ -578,7 +579,7 @@ resource_size_t pcibios_align_resource(void *data, const struct resource *res, start, size, align); if (res->flags & IORESOURCE_MEM) - return pci_align_resource(dev, res, empty_res, size, align); + return pci_align_resource(rr, res, empty_res, size, align); return start; }diff --git a/arch/m68k/kernel/pcibios.c b/arch/m68k/kernel/pcibios.c index 7a9e60df79c5..3024408412bc 100644 --- a/arch/m68k/kernel/pcibios.c +++ b/arch/m68k/kernel/pcibios.c@@ -31,14 +31,14 @@ resource_size_t pcibios_align_resource(void *data, const struct resource *res, resource_size_t size, resource_size_t align) { - struct pci_dev *dev = data; + struct pci_resreq_data *rr = data; resource_size_t start = res->start; if ((res->flags & IORESOURCE_IO) && (start & 0x300)) start = (start + 0x3ff) & ~0x3ff; if (res->flags & IORESOURCE_MEM) - return pci_align_resource(dev, res, empty_res, size, align); + return pci_align_resource(rr, res, empty_res, size, align); return start; }diff --git a/arch/mips/pci/pci-generic.c b/arch/mips/pci/pci-generic.c index c2e23d0c1d77..7f3ecb91b85b 100644 --- a/arch/mips/pci/pci-generic.c +++ b/arch/mips/pci/pci-generic.c@@ -25,7 +25,8 @@ resource_size_t pcibios_align_resource(void *data, const struct resource *res, const struct resource *empty_res, resource_size_t size, resource_size_t align) { - struct pci_dev *dev = data; + struct pci_resreq_data *rr = data; + struct pci_dev *dev = rr->dev; resource_size_t start = res->start; struct pci_host_bridge *host_bridge;@@ -39,7 +40,7 @@ resource_size_t pcibios_align_resource(void *data, const struct resource *res, start, size, align); if (res->flags & IORESOURCE_MEM) - return pci_align_resource(dev, res, empty_res, size, align); + return pci_align_resource(rr, res, empty_res, size, align); return start; }diff --git a/arch/mips/pci/pci-legacy.c b/arch/mips/pci/pci-legacy.c index dae6dafdd6e0..82d4b01db64e 100644 --- a/arch/mips/pci/pci-legacy.c +++ b/arch/mips/pci/pci-legacy.c@@ -55,7 +55,8 @@ pcibios_align_resource(void *data, const struct resource *res, const struct resource *empty_res, resource_size_t size, resource_size_t align) { - struct pci_dev *dev = data; + struct pci_resreq_data *rr = data; + struct pci_dev *dev = rr->dev; struct pci_controller *hose = dev->sysdata; resource_size_t start = res->start;@@ -70,7 +71,7 @@ pcibios_align_resource(void *data, const struct resource *res, if (start & 0x300) start = (start + 0x3ff) & ~0x3ff; } else if (res->flags & IORESOURCE_MEM) { - start = pci_align_resource(dev, res, empty_res, size, align); + start = pci_align_resource(rr, res, empty_res, size, align); /* Make sure we start at our min on all hoses */ if (start < PCIBIOS_MIN_MEM + hose->mem_resource->start)diff --git a/arch/parisc/kernel/pci.c b/arch/parisc/kernel/pci.c index 518f532ccddc..d582be996051 100644 --- a/arch/parisc/kernel/pci.c +++ b/arch/parisc/kernel/pci.c@@ -193,7 +193,8 @@ resource_size_t pcibios_align_resource(void *data, const struct resource *res, resource_size_t size, resource_size_t alignment) { - struct pci_dev *dev = data; + struct pci_resreq_data *rr = data; + struct pci_dev *dev = rr->dev; resource_size_t align, start = res->start; pci_dbg(dev, "%pR: pcibios_align_resource(%lx, 0x%llx, 0x%llx), parent %pR\n",@@ -205,7 +206,7 @@ resource_size_t pcibios_align_resource(void *data, const struct resource *res, if (align > alignment) start = ALIGN(start, align); else - start = pci_align_resource(dev, res, empty_res, size, alignment); + start = pci_align_resource(rr, res, empty_res, size, alignment); return start; }diff --git a/arch/powerpc/kernel/pci-common.c b/arch/powerpc/kernel/pci-common.c index 4fc52c21fe5d..23594759cfe2 100644 --- a/arch/powerpc/kernel/pci-common.c +++ b/arch/powerpc/kernel/pci-common.c@@ -1131,7 +1131,8 @@ resource_size_t pcibios_align_resource(void *data, const struct resource *res, resource_size_t size, resource_size_t align) { - struct pci_dev *dev = data; + struct pci_resreq_data *rr = data; + struct pci_dev *dev = rr->dev; resource_size_t start = res->start; if (res->flags & IORESOURCE_IO) {@@ -1140,7 +1141,7 @@ resource_size_t pcibios_align_resource(void *data, const struct resource *res, if (start & 0x300) start = (start + 0x3ff) & ~0x3ff; } else if (res->flags & IORESOURCE_MEM) { - start = pci_align_resource(dev, res, empty_res, size, align); + start = pci_align_resource(rr, res, empty_res, size, align); } return start;diff --git a/arch/sh/drivers/pci/pci.c b/arch/sh/drivers/pci/pci.c index 878a27a1acfb..279f2770ff4b 100644 --- a/arch/sh/drivers/pci/pci.c +++ b/arch/sh/drivers/pci/pci.c@@ -172,7 +172,8 @@ resource_size_t pcibios_align_resource(void *data, const struct resource *res, resource_size_t size, resource_size_t align) { - struct pci_dev *dev = data; + struct pci_resreq_data *rr = data; + struct pci_dev *dev = rr->dev; struct pci_channel *hose = dev->sysdata; resource_size_t start = res->start;@@ -186,7 +187,7 @@ resource_size_t pcibios_align_resource(void *data, const struct resource *res, if (start & 0x300) start = (start + 0x3ff) & ~0x3ff; } else if (res->flags & IORESOURCE_MEM) { - start = pci_align_resource(dev, res, empty_res, size, align); + start = pci_align_resource(rr, res, empty_res, size, align); } return start;diff --git a/arch/x86/pci/i386.c b/arch/x86/pci/i386.c index e2de26b82940..4178ae4380c2 100644 --- a/arch/x86/pci/i386.c +++ b/arch/x86/pci/i386.c@@ -156,7 +156,8 @@ pcibios_align_resource(void *data, const struct resource *res, const struct resource *empty_res, resource_size_t size, resource_size_t align) { - struct pci_dev *dev = data; + struct pci_resreq_data *rr = data; + struct pci_dev *dev = rr->dev; resource_size_t start = res->start; if (res->flags & IORESOURCE_IO) {@@ -165,7 +166,7 @@ pcibios_align_resource(void *data, const struct resource *res, if (start & 0x300) start = (start + 0x3ff) & ~0x3ff; } else if (res->flags & IORESOURCE_MEM) { - start = pci_align_resource(dev, res, empty_res, size, align); + start = pci_align_resource(rr, res, empty_res, size, align); /* The low 1MB range is reserved for ISA cards */ if (start < BIOS_END)diff --git a/arch/xtensa/kernel/pci.c b/arch/xtensa/kernel/pci.c index 305031551136..4e8ad4a3c9fe 100644 --- a/arch/xtensa/kernel/pci.c +++ b/arch/xtensa/kernel/pci.c@@ -42,7 +42,8 @@ pcibios_align_resource(void *data, const struct resource *res, const struct resource *empty_res, resource_size_t size, resource_size_t align) { - struct pci_dev *dev = data; + struct pci_resreq_data *rr = data; + struct pci_dev *dev = rr->dev; resource_size_t start = res->start; if (res->flags & IORESOURCE_IO) {@@ -55,7 +56,7 @@ pcibios_align_resource(void *data, const struct resource *res, if (start & 0x300) start = (start + 0x3ff) & ~0x3ff; } else if (res->flags & IORESOURCE_MEM) { - start = pci_align_resource(dev, res, empty_res, size, align); + start = pci_align_resource(rr, res, empty_res, size, align); } return start;diff --git a/drivers/char/agp/intel-gtt.c b/drivers/char/agp/intel-gtt.c index bcc26785175d..2214347906a6 100644 --- a/drivers/char/agp/intel-gtt.c +++ b/drivers/char/agp/intel-gtt.c@@ -1038,10 +1038,13 @@ static struct agp_memory *intel_fake_agp_alloc_by_type(size_t pg_count, static int intel_alloc_chipset_flush_resource(void) { + struct pci_resreq_data rr; int ret; + + pci_init_pci_resreq_data(&rr, intel_private.bridge_dev); ret = pci_bus_alloc_resource(intel_private.bridge_dev->bus, &intel_private.ifp_resource, PAGE_SIZE, PAGE_SIZE, PCIBIOS_MIN_MEM, 0, - pcibios_align_resource, intel_private.bridge_dev); + pcibios_align_resource, &rr); return ret; }diff --git a/drivers/gpu/drm/i915/i915_gmch.c b/drivers/gpu/drm/i915/i915_gmch.c index b0ef6ef577a3..d35097bebc0f 100644 --- a/drivers/gpu/drm/i915/i915_gmch.c +++ b/drivers/gpu/drm/i915/i915_gmch.c@@ -38,6 +38,7 @@ static int mchbar_reg(struct drm_i915_private *i915) static int intel_alloc_mchbar_resource(struct drm_i915_private *i915) { + struct pci_resreq_data rr; u32 temp_lo, temp_hi = 0; u64 mchbar_addr; int ret;@@ -55,12 +56,12 @@ intel_alloc_mchbar_resource(struct drm_i915_private *i915) /* Get some space for it */ i915->gmch.mch_res.name = "i915 MCHBAR"; i915->gmch.mch_res.flags = IORESOURCE_MEM; + pci_init_pci_resreq_data(&rr, i915->gmch.pdev); ret = pci_bus_alloc_resource(i915->gmch.pdev->bus, &i915->gmch.mch_res, MCHBAR_SIZE, MCHBAR_SIZE, PCIBIOS_MIN_MEM, - 0, pcibios_align_resource, - i915->gmch.pdev); + 0, pcibios_align_resource, &rr); if (ret) { drm_dbg(&i915->drm, "failed bus alloc: %d\n", ret); i915->gmch.mch_res.start = 0;diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c index b2879a6be5f8..1b7a4469c6ca 100644 --- a/drivers/pci/pci.c +++ b/drivers/pci/pci.c@@ -6444,8 +6444,8 @@ static DEFINE_SPINLOCK(resource_alignment_lock); * RETURNS: Resource alignment if it is specified. * Zero if it is not specified. */ -static resource_size_t pci_specified_resource_alignment(struct pci_dev *dev, - bool *resize) +resource_size_t pci_specified_resource_alignment(struct pci_dev *dev, + bool *resize) { int align_order, count; resource_size_t align = pcibios_default_alignment();@@ -6497,6 +6497,7 @@ static resource_size_t pci_specified_resource_alignment(struct pci_dev *dev, spin_unlock(&resource_alignment_lock); return align; } +EXPORT_SYMBOL_GPL(pci_specified_resource_alignment); static void pci_request_resource_alignment(struct pci_dev *dev, int bar, resource_size_t align, bool resize)diff --git a/drivers/pci/setup-res.c b/drivers/pci/setup-res.c index 376f09630a4a..441a62807719 100644 --- a/drivers/pci/setup-res.c +++ b/drivers/pci/setup-res.c@@ -265,17 +265,21 @@ resource_size_t pci_resource_alignment(const struct pci_dev *dev, * before res->start if there's enough free space there. This enables * tighter packing for resources. */ -resource_size_t pci_align_resource(struct pci_dev *dev, +resource_size_t pci_align_resource(struct pci_resreq_data *rr, const struct resource *res, const struct resource *empty_res, resource_size_t size, resource_size_t align) { + struct pci_dev *dev = rr->dev; resource_size_t remainder, start_addr; if (!(res->flags & IORESOURCE_MEM)) return res->start; + if (rr->user_align) + return res->start; + if (IS_ALIGNED(size, align)) return res->start;@@ -306,18 +310,21 @@ resource_size_t __weak pcibios_align_resource(void *data, resource_size_t size, resource_size_t align) { - struct pci_dev *dev = data; + struct pci_resreq_data *rr = data; - return pci_align_resource(dev, res, empty_res, size, align); + return pci_align_resource(rr, res, empty_res, size, align); } static int __pci_assign_resource(struct pci_bus *bus, struct pci_dev *dev, int resno, resource_size_t size, resource_size_t align) { struct resource *res = pci_resource_n(dev, resno); + struct pci_resreq_data rr; resource_size_t min; int ret; + pci_init_pci_resreq_data(&rr, dev); + min = (res->flags & IORESOURCE_IO) ? PCIBIOS_MIN_IO : PCIBIOS_MIN_MEM; /*@@ -329,7 +336,7 @@ static int __pci_assign_resource(struct pci_bus *bus, struct pci_dev *dev, */ ret = pci_bus_alloc_resource(bus, res, size, align, min, IORESOURCE_PREFETCH | IORESOURCE_MEM_64, - pcibios_align_resource, dev); + pcibios_align_resource, &rr); if (ret == 0) return 0;@@ -341,7 +348,7 @@ static int __pci_assign_resource(struct pci_bus *bus, struct pci_dev *dev, (IORESOURCE_PREFETCH | IORESOURCE_MEM_64)) { ret = pci_bus_alloc_resource(bus, res, size, align, min, IORESOURCE_PREFETCH, - pcibios_align_resource, dev); + pcibios_align_resource, &rr); if (ret == 0) return 0; }@@ -354,7 +361,7 @@ static int __pci_assign_resource(struct pci_bus *bus, struct pci_dev *dev, */ if (res->flags & (IORESOURCE_PREFETCH | IORESOURCE_MEM_64)) ret = pci_bus_alloc_resource(bus, res, size, align, min, 0, - pcibios_align_resource, dev); + pcibios_align_resource, &rr); return ret; }diff --git a/include/linux/pci.h b/include/linux/pci.h index d31a8d107b1e..fe0233f0d9e6 100644 --- a/include/linux/pci.h +++ b/include/linux/pci.h@@ -1217,12 +1217,34 @@ int __must_check pcibios_enable_device(struct pci_dev *, int mask); /* Architecture-specific versions may override this (weak) */ char *pcibios_setup(char *str); -/* Used only when drivers/pci/setup.c is used */ +/* Resource assignment request handling */ +/** + * struct pci_resreq_data - Data passed to pcibios_align_resource() + * @dev: PCI device + * @user_align: User provided alignment override (pci=resource_alignment param) + */ +struct pci_resreq_data { + struct pci_dev *dev; + resource_size_t user_align; +}; + +resource_size_t pci_specified_resource_alignment(struct pci_dev *dev, + bool *resize); +static inline void pci_init_pci_resreq_data(struct pci_resreq_data *rr, + struct pci_dev *dev) +{ + bool user_aligned; + + memset(rr, 0, sizeof(*rr)); + rr->dev = dev; + rr->user_align = pci_specified_resource_alignment(dev, &user_aligned); +} + resource_size_t pcibios_align_resource(void *data, const struct resource *res, const struct resource *empty_res, resource_size_t size, resource_size_t align); -resource_size_t pci_align_resource(struct pci_dev *dev, +resource_size_t pci_align_resource(struct pci_resreq_data *rr, const struct resource *res, const struct resource *empty_res, resource_size_t size,
-- Jani Nikula, Intel