Re: [PATCH v4 2/5] PCI: dwc: ep: Add 'address' alignment to 'size' check in dw_pcie_prog_ep_inbound_atu()

[Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>]

On Fri, Nov 22, 2024 at 12:57:11PM +0100, Niklas Cassel wrote:
> dw_pcie_prog_ep_inbound_atu() is used to program an inbound iATU in
> "BAR Match Mode".
> 
> A memory address returned by e.g. kmalloc() is guaranteed to have natural
> alignment (aligned to the size of the allocation). It is however not
> guaranteed that pci_epc_set_bar() (and thus dw_pcie_prog_ep_inbound_atu())
> is supplied an address that has natural alignment. (An EPF driver can send
> in an arbitrary physical address to pci_epc_set_bar().)
> 
> The DWC Databook description for the LWR_TARGET_RW and LWR_TARGET_HW fields
> in the IATU_LWR_TARGET_ADDR_OFF_INBOUND_i registers state that:
> "Field size depends on log2(BAR_MASK+1) in BAR match mode."
> 
> I.e. only the upper bits are writable, and the number of writable bits is
> dependent on the configured BAR_MASK.
> 
> Add a check to ensure that the physical address programmed in the iATU is
> aligned to the size of the BAR (BAR_MASK+1), as without this, we can get
> hard to debug errors, as we could write to bits that are read-only (without
> getting a write error), which could cause the iATU to end up redirecting to
> a physical address that is different from the address that we intended.
> 
> Signed-off-by: Niklas Cassel <cassel@kernel.org>

Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>

- Mani

> ---
>  drivers/pci/controller/dwc/pcie-designware-ep.c | 8 +++++---
>  drivers/pci/controller/dwc/pcie-designware.c    | 5 +++--
>  drivers/pci/controller/dwc/pcie-designware.h    | 2 +-
>  3 files changed, 9 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/pci/controller/dwc/pcie-designware-ep.c b/drivers/pci/controller/dwc/pcie-designware-ep.c
> index 34d60142ffb5..ff4350e7adb6 100644
> --- a/drivers/pci/controller/dwc/pcie-designware-ep.c
> +++ b/drivers/pci/controller/dwc/pcie-designware-ep.c
> @@ -128,7 +128,8 @@ static int dw_pcie_ep_write_header(struct pci_epc *epc, u8 func_no, u8 vfunc_no,
>  }
>  
>  static int dw_pcie_ep_inbound_atu(struct dw_pcie_ep *ep, u8 func_no, int type,
> -				  dma_addr_t cpu_addr, enum pci_barno bar)
> +				  dma_addr_t cpu_addr, enum pci_barno bar,
> +				  size_t size)
>  {
>  	int ret;
>  	u32 free_win;
> @@ -145,7 +146,7 @@ static int dw_pcie_ep_inbound_atu(struct dw_pcie_ep *ep, u8 func_no, int type,
>  	}
>  
>  	ret = dw_pcie_prog_ep_inbound_atu(pci, func_no, free_win, type,
> -					  cpu_addr, bar);
> +					  cpu_addr, bar, size);
>  	if (ret < 0) {
>  		dev_err(pci->dev, "Failed to program IB window\n");
>  		return ret;
> @@ -265,7 +266,8 @@ static int dw_pcie_ep_set_bar(struct pci_epc *epc, u8 func_no, u8 vfunc_no,
>  	else
>  		type = PCIE_ATU_TYPE_IO;
>  
> -	ret = dw_pcie_ep_inbound_atu(ep, func_no, type, epf_bar->phys_addr, bar);
> +	ret = dw_pcie_ep_inbound_atu(ep, func_no, type, epf_bar->phys_addr, bar,
> +				     size);
>  	if (ret)
>  		return ret;
>  
> diff --git a/drivers/pci/controller/dwc/pcie-designware.c b/drivers/pci/controller/dwc/pcie-designware.c
> index 6d6cbc8b5b2c..3c683b6119c3 100644
> --- a/drivers/pci/controller/dwc/pcie-designware.c
> +++ b/drivers/pci/controller/dwc/pcie-designware.c
> @@ -597,11 +597,12 @@ int dw_pcie_prog_inbound_atu(struct dw_pcie *pci, int index, int type,
>  }
>  
>  int dw_pcie_prog_ep_inbound_atu(struct dw_pcie *pci, u8 func_no, int index,
> -				int type, u64 cpu_addr, u8 bar)
> +				int type, u64 cpu_addr, u8 bar, size_t size)
>  {
>  	u32 retries, val;
>  
> -	if (!IS_ALIGNED(cpu_addr, pci->region_align))
> +	if (!IS_ALIGNED(cpu_addr, pci->region_align) ||
> +	    !IS_ALIGNED(cpu_addr, size))
>  		return -EINVAL;
>  
>  	dw_pcie_writel_atu_ib(pci, index, PCIE_ATU_LOWER_TARGET,
> diff --git a/drivers/pci/controller/dwc/pcie-designware.h b/drivers/pci/controller/dwc/pcie-designware.h
> index 347ab74ac35a..fc0872711672 100644
> --- a/drivers/pci/controller/dwc/pcie-designware.h
> +++ b/drivers/pci/controller/dwc/pcie-designware.h
> @@ -491,7 +491,7 @@ int dw_pcie_prog_outbound_atu(struct dw_pcie *pci,
>  int dw_pcie_prog_inbound_atu(struct dw_pcie *pci, int index, int type,
>  			     u64 cpu_addr, u64 pci_addr, u64 size);
>  int dw_pcie_prog_ep_inbound_atu(struct dw_pcie *pci, u8 func_no, int index,
> -				int type, u64 cpu_addr, u8 bar);
> +				int type, u64 cpu_addr, u8 bar, size_t size);
>  void dw_pcie_disable_atu(struct dw_pcie *pci, u32 dir, int index);
>  void dw_pcie_setup(struct dw_pcie *pci);
>  void dw_pcie_iatu_detect(struct dw_pcie *pci);
> -- 
> 2.47.0
> 

-- 
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