* [PATCH v5 08/14] PCI: Honor alignment overrides
[not found] <20261106134341.39493-1-ilpo.jarvinen@linux.intel.com>
@ 2026-11-06 13:43 ` Ilpo Järvinen
0 siblings, 0 replies; only message in thread
From: Ilpo Järvinen @ 2026-11-06 13:43 UTC (permalink / raw)
To: Maciej Grochowski, Geramy Loveless, Eric Auger, Alexey Fomenko,
Bjorn Helgaas, linux-pci, Lorenzo Pieralisi, Rob Herring,
Krzysztof Wilczyński, Mesih Kilinc, Richard Henderson,
Matt Turner, Magnus Lindholm, Russell King, Geert Uytterhoeven,
Thomas Bogendoerfer, James E.J. Bottomley, Helge Deller,
Madhavan Srinivasan, Michael Ellerman, Nicholas Piggin,
Christophe Leroy (CS GROUP), Ritesh Harjani (IBM),
Shrikanth Hegde, Yoshinori Sato, Rich Felker,
John Paul Adrian Glaubitz, Thomas Gleixner, Ingo Molnar,
Borislav Petkov, Dave Hansen, x86, H. Peter Anvin, Chris Zankel,
Max Filippov, David Airlie, Jani Nikula, Joonas Lahtinen,
Rodrigo Vivi, Tvrtko Ursulin, Simona Vetter, Ilpo Järvinen,
linux-alpha, linux-kernel, linux-arm-kernel, linux-m68k,
linux-mips, linux-parisc, linuxppc-dev, linux-sh, dri-devel,
intel-gfx
Cc: Sashiko
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.
PowerNV will not be able to use the current remainder logic after this
change because on it pcibios_default_alignment() always results in
setting min_align but this code is in a transient state and the problem
will be fixed by an upcoming change that rewrites the resource
placement algorithm with a more generic approach.
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/
Acked-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
---
Jani Nikula <jani.nikula@intel.com> did ack this with a condition that
there is a proper review done by somebody else so I've not yet included
his tag.
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 | 4 ++--
drivers/pci/pci.h | 2 ++
drivers/pci/setup-res.c | 33 ++++++++++++++++++++++++++------
include/linux/pci.h | 15 +++++++++++++--
16 files changed, 79 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 96950fe9c2b7..36a3a439f609 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)\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..06990fad8e48 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_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..f11ed5509095 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_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 7c6f2aba8144..8c40f86d75ee 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -6507,8 +6507,8 @@ 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();
diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
index 77efa4c5c960..e6e2afcceb33 100644
--- a/drivers/pci/pci.h
+++ b/drivers/pci/pci.h
@@ -515,6 +515,8 @@ void devm_pci_alloc_host_bridge_release(void *data);
struct device *pci_get_host_bridge_device(struct pci_dev *dev);
void pci_put_host_bridge_device(struct device *dev);
+resource_size_t pci_specified_resource_alignment(struct pci_dev *dev,
+ bool *resize);
void pci_resize_resource_set_size(struct pci_dev *dev, int resno, int size);
int pci_do_resource_release_and_resize(struct pci_dev *dev, int resno, int size,
int exclude_bars);
diff --git a/drivers/pci/setup-res.c b/drivers/pci/setup-res.c
index 376f09630a4a..9c55b9f9462c 100644
--- a/drivers/pci/setup-res.c
+++ b/drivers/pci/setup-res.c
@@ -248,6 +248,20 @@ static int pci_revert_fw_address(struct resource *res, struct pci_dev *dev,
return 0;
}
+/*
+ * TODO: Improve PCI resource assignment interface so that callers outside PCI
+ * core do not need to know about this detail.
+ */
+void pci_init_resreq_data(struct pci_resreq_data *rr, struct pci_dev *dev)
+{
+ bool dummy;
+
+ memset(rr, 0, sizeof(*rr));
+ rr->dev = dev;
+ rr->min_align = pci_specified_resource_alignment(dev, &dummy);
+}
+EXPORT_SYMBOL_GPL(pci_init_resreq_data);
+
resource_size_t pci_resource_alignment(const struct pci_dev *dev,
const struct resource *res)
{
@@ -265,17 +279,21 @@ 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->min_align)
+ return res->start;
+
if (IS_ALIGNED(size, align))
return res->start;
@@ -306,18 +324,21 @@ 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_resreq_data(&rr, dev);
+
min = (res->flags & IORESOURCE_IO) ? PCIBIOS_MIN_IO : PCIBIOS_MIN_MEM;
/*
@@ -329,7 +350,7 @@ 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 +362,7 @@ 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 +375,7 @@ 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 aa3765a20a96..c945f5753e7c 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -1221,12 +1221,23 @@ 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 */
+/**
+ * struct pci_resreq_data - Data passed to pcibios_align_resource()
+ * @dev: PCI device
+ * @min_align: Minimum alignment bound (from pci=resource_alignment or arch)
+ */
+struct pci_resreq_data {
+ struct pci_dev *dev;
+ resource_size_t min_align;
+};
+
+void pci_init_resreq_data(struct pci_resreq_data *rr, struct pci_dev *dev);
+
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,
--
2.47.3
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2026-11-06 13:43 ` [PATCH v5 08/14] PCI: Honor alignment overrides Ilpo Järvinen
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