[PATCH 0/2] PCI: dwc: Support large BARs on UltraRISC DP1000

[PATCH 0/2] PCI: dwc: Support large BARs on UltraRISC DP1000

[Xincheng Zhang]

This series lets DWC host drivers skip generic outbound iATU programming
for host bridge MEM ranges, which is useful for some compute cards' very
large BAR size demand (>100GB).

DP1000 has 16 outbound iATU windows, and each window can map up to
4GB. This limits its allocatable MEM64 BAR size to 4GB*(16-3)=52GB
(-3 for CFG, I/O and MEM32).

But some EPs like compute cards demand large BAR size that exceeds the
mapping limit of the 13 iATUs. DWC IP spec allows RC to skip MEM iATU setup
and simply uses a direct mapping. By introducing a `bypass_ob_mem_iatu`
flag at the RC level, this patch enables large BARs on UR-DP1000
RISC-V CPU.

Tested on UltraRISC DP1000 EVB and Titan board. The system booted
successfully with PCIe links up on all three controllers and NVMe rootfs
mounted. MMIO read/write speed test within the large BAR space goes well.

Xincheng Zhang (2):
  PCI: dwc: Allow drivers to skip MEM outbound iATU setup
  PCI: ultrarisc: Skip MEM outbound iATU setup on DP1000

 drivers/pci/controller/dwc/pcie-designware-host.c | 6 +++---
 drivers/pci/controller/dwc/pcie-designware.h      | 1 +
 drivers/pci/controller/dwc/pcie-ultrarisc.c       | 6 ++++++
 3 files changed, 10 insertions(+), 3 deletions(-)

-- 
2.34.1

[PATCH 1/2] PCI: dwc: Allow drivers to skip MEM outbound iATU setup

[Xincheng Zhang]

Some DWC-based controllers do not require outbound iATU windows for MEM
transactions. For those platforms, programming outbound iATU windows for
host bridge MEM ranges is unnecessary and may constrain the available MEM
aperture.

Add dw_pcie_rp::bypass_ob_mem_iatu so drivers can skip generic MEM iATU
setup while using the common DWC host init path.

Existing drivers keep the current behavior because the flag defaults to
false. The I/O iATU setup does not use the MEM resource iterator, and the
iterator may be uninitialized when MEM setup is skipped. Avoid using it in
the I/O iATU error path.

Signed-off-by: Xincheng Zhang <zhangxincheng@ultrarisc.com>
---
 drivers/pci/controller/dwc/pcie-designware-host.c | 6 +++---
 drivers/pci/controller/dwc/pcie-designware.h      | 1 +
 2 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/pci/controller/dwc/pcie-designware-host.c b/drivers/pci/controller/dwc/pcie-designware-host.c
index f5a38e6fd8d79..3c5f5ff080818 100644
--- a/drivers/pci/controller/dwc/pcie-designware-host.c
+++ b/drivers/pci/controller/dwc/pcie-designware-host.c
@@ -911,7 +911,8 @@ static int dw_pcie_iatu_setup(struct dw_pcie_rp *pp)
 	resource_list_for_each_entry(entry, &pp->bridge->windows) {
 		resource_size_t res_size;
 
-		if (resource_type(entry->res) != IORESOURCE_MEM)
+		if (pp->bypass_ob_mem_iatu ||
+		    resource_type(entry->res) != IORESOURCE_MEM)
 			continue;
 
 		atu.type = PCIE_TLP_TYPE_MEM_RDWR;
@@ -964,8 +965,7 @@ static int dw_pcie_iatu_setup(struct dw_pcie_rp *pp)
 
 			ret = dw_pcie_prog_outbound_atu(pci, &atu);
 			if (ret) {
-				dev_err(pci->dev, "Failed to set IO range %pr\n",
-					entry->res);
+				dev_err(pci->dev, "Failed to set IO range\n");
 				return ret;
 			}
 			ob_iatu_index++;
diff --git a/drivers/pci/controller/dwc/pcie-designware.h b/drivers/pci/controller/dwc/pcie-designware.h
index 0735ae9409240..d89badcca2689 100644
--- a/drivers/pci/controller/dwc/pcie-designware.h
+++ b/drivers/pci/controller/dwc/pcie-designware.h
@@ -469,6 +469,7 @@ struct dw_pcie_rp {
 	struct pci_config_window *cfg;
 	bool			ecam_enabled;
 	bool			native_ecam;
+	bool			bypass_ob_mem_iatu;
 	bool                    skip_l23_ready;
 	bool			skip_pwrctrl_off;
 };
-- 
2.34.1

Re: [PATCH 1/2] PCI: dwc: Allow drivers to skip MEM outbound iATU setup

[sashiko-bot]

> Some DWC-based controllers do not require outbound iATU windows for MEM
> transactions. For those platforms, programming outbound iATU windows for
> host bridge MEM ranges is unnecessary and may constrain the available MEM
> aperture.
> 
> Add dw_pcie_rp::bypass_ob_mem_iatu so drivers can skip generic MEM iATU
> setup while using the common DWC host init path.
> 
> Existing drivers keep the current behavior because the flag defaults to
> false. The I/O iATU setup does not use the MEM resource iterator, and the
> iterator may be uninitialized when MEM setup is skipped. Avoid using it in
> the I/O iATU error path.
> 
> Signed-off-by: Xincheng Zhang <zhangxincheng@ultrarisc.com>

Sashiko has reviewed this patch and found no issues. It looks great!

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260827055448.1818858-1-zhangxincheng@ultrarisc.com?part=1

[PATCH 2/2] PCI: ultrarisc: Skip MEM outbound iATU setup on DP1000

[Xincheng Zhang]

DP1000 has 16 outbound iATU windows and each window can map up to 4GB. One
window is used for CFG accesses, one for I/O space and one for the 32-bit
MEM aperture, leaving only 13 windows for the 64-bit MEM aperture.

This limits the 64-bit MEM aperture that can be described with outbound
iATU windows. DP1000 routes MEM transactions without using outbound iATU
windows, so skip generic DWC MEM outbound iATU setup to allow a larger
64-bit MEM aperture.

Set dw_pcie_rp::bypass_ob_mem_iatu for this controller.

Signed-off-by: Xincheng Zhang <zhangxincheng@ultrarisc.com>
---
 drivers/pci/controller/dwc/pcie-ultrarisc.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/pci/controller/dwc/pcie-ultrarisc.c b/drivers/pci/controller/dwc/pcie-ultrarisc.c
index 51e89180490d4..0d4989a0f3afc 100644
--- a/drivers/pci/controller/dwc/pcie-ultrarisc.c
+++ b/drivers/pci/controller/dwc/pcie-ultrarisc.c
@@ -154,6 +154,12 @@ static int ultrarisc_pcie_probe(struct platform_device *pdev)
 
 	pp = &pci->pp;
 
+	/*
+	 * DP1000 routes MEM transactions without outbound iATU windows, which
+	 * avoids the 16-window/4GB-per-window aperture limit.
+	 */
+	pp->bypass_ob_mem_iatu = true;
+
 	platform_set_drvdata(pdev, ultra);
 
 	ret = ultrarisc_pcie_init_clks(ultra);
-- 
2.34.1

Re: [PATCH 2/2] PCI: ultrarisc: Skip MEM outbound iATU setup on DP1000

[sashiko-bot]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:

Pre-existing issues:
- [High] Missing driver `.remove` callback causes a Use-After-Free of PCI host bridge structures when the module is unloaded.
--

commit e72827a32cf8b1eb87517edbf6b7e64e76f36134
Author: Xincheng Zhang <zhangxincheng@ultrarisc.com>

PCI: ultrarisc: Skip MEM outbound iATU setup on DP1000

The DP1000 has 16 outbound iATU windows, one of which is used for the
32-bit MEM aperture. To avoid limiting the 64-bit MEM aperture to the
remaining 13 windows, this commit skips generic DWC MEM outbound iATU
setup, allowing transactions to bypass outbound iATU windows.

> diff --git a/drivers/pci/controller/dwc/pcie-ultrarisc.c b/drivers/pci/controller/dwc/pcie-ultrarisc.c
> index 51e89180490d4..0d4989a0f3afc 100644
> --- a/drivers/pci/controller/dwc/pcie-ultrarisc.c
> +++ b/drivers/pci/controller/dwc/pcie-ultrarisc.c
> @@ -154,6 +154,12 @@ static int ultrarisc_pcie_probe(struct platform_device *pdev)
>  
>  	pp = &pci->pp;
>  
> +	/*
> +	 * DP1000 routes MEM transactions without outbound iATU windows, which
> +	 * avoids the 16-window/4GB-per-window aperture limit.
> +	 */
> +	pp->bypass_ob_mem_iatu = true;
> +
>  	platform_set_drvdata(pdev, ultra);
>  
>  	ret = ultrarisc_pcie_init_clks(ultra);

[Severity: High]
This is a pre-existing issue, but since you are modifying the probe path,
I noticed that ultrarisc_pcie_probe() calls dw_pcie_host_init() which allocates
a PCI host bridge via devres, yet the platform driver lacks a remove callback.

Because the driver registers with module_platform_driver():

static struct platform_driver ultrarisc_pcie_driver = {
	.driver = {
		.name = "ultrarisc-pcie",
		...
	},
	.probe = ultrarisc_pcie_probe,
};
module_platform_driver(ultrarisc_pcie_driver);

Is it possible for a privileged user to unload the module and trigger a
use-after-free?

When the module is unloaded, devres will automatically free the memory for the
pci_host_bridge. Because there is no remove callback in the driver,
dw_pcie_host_deinit() is never invoked to call pci_stop_root_bus() and
pci_remove_root_bus().

Does this leave the PCI core with active references to the freed host bridge
structures after the module is removed?

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260827055448.1818858-1-zhangxincheng@ultrarisc.com?part=2