Re: [PATCH v1 1/1] PCI: dwc: Fix MSI msi_msg dma mapping

[Bjorn Helgaas <helgaas@kernel.org>]

On Wed, May 25, 2022 at 10:33:16PM +0000, Will McVicker wrote:
> As of commit 07940c369a6b ("PCI: dwc: Fix MSI page leakage in
> suspend/resume"), the PCIe designware host driver has been using the
> driver data allocation for the msi_msg dma mapping which can result in
> a DMA_MAPPING_ERROR due to the DMA overflow check in
> dma_direct_map_page() when the address is greater than 32-bits (reported
> in [1]). The commit was trying to address a memory leak on
> suspend/resume by moving the MSI mapping to dw_pcie_host_init(), but
> subsequently dropped the page allocation thinking it wasn't needed.
> 
> To fix the DMA mapping issue as well as make msi_msg DMA'able, let's
> switch back to allocating a 32-bit page for the msi_msg. To avoid the
> suspend/resume leak, we can allocate the page in dw_pcie_host_init()
> since that function shouldn't be called during suspend/resume.
> 
> [1] https://lore.kernel.org/all/Yo0soniFborDl7+C@google.com/
> 
> Signed-off-by: Will McVicker <willmcvicker@google.com>

Applied to pci/ctrl/dwc for v5.20, thanks!

> ---
>  drivers/pci/controller/dwc/pcie-designware-host.c | 14 ++++++++------
>  drivers/pci/controller/dwc/pcie-designware.h      |  2 +-
>  2 files changed, 9 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/pci/controller/dwc/pcie-designware-host.c b/drivers/pci/controller/dwc/pcie-designware-host.c
> index 2fa86f32d964..3655c6f88bf1 100644
> --- a/drivers/pci/controller/dwc/pcie-designware-host.c
> +++ b/drivers/pci/controller/dwc/pcie-designware-host.c
> @@ -267,8 +267,9 @@ static void dw_pcie_free_msi(struct pcie_port *pp)
>  		struct dw_pcie *pci = to_dw_pcie_from_pp(pp);
>  		struct device *dev = pci->dev;
>  
> -		dma_unmap_single_attrs(dev, pp->msi_data, sizeof(pp->msi_msg),
> -				       DMA_FROM_DEVICE, DMA_ATTR_SKIP_CPU_SYNC);
> +		dma_unmap_page(dev, pp->msi_data, PAGE_SIZE, DMA_FROM_DEVICE);
> +		if (pp->msi_page)
> +			__free_page(pp->msi_page);
>  	}
>  }
>  
> @@ -392,12 +393,13 @@ int dw_pcie_host_init(struct pcie_port *pp)
>  			if (ret)
>  				dev_warn(pci->dev, "Failed to set DMA mask to 32-bit. Devices with only 32-bit MSI support may not work properly\n");
>  
> -			pp->msi_data = dma_map_single_attrs(pci->dev, &pp->msi_msg,
> -						      sizeof(pp->msi_msg),
> -						      DMA_FROM_DEVICE,
> -						      DMA_ATTR_SKIP_CPU_SYNC);
> +			pp->msi_page = alloc_page(GFP_DMA32);
> +			pp->msi_data = dma_map_page(pci->dev, pp->msi_page, 0, PAGE_SIZE,
> +						    DMA_FROM_DEVICE);
>  			if (dma_mapping_error(pci->dev, pp->msi_data)) {
>  				dev_err(pci->dev, "Failed to map MSI data\n");
> +				__free_page(pp->msi_page);
> +				pp->msi_page = NULL;
>  				pp->msi_data = 0;
>  				goto err_free_msi;
>  			}
> diff --git a/drivers/pci/controller/dwc/pcie-designware.h b/drivers/pci/controller/dwc/pcie-designware.h
> index 7d6e9b7576be..b5f528536358 100644
> --- a/drivers/pci/controller/dwc/pcie-designware.h
> +++ b/drivers/pci/controller/dwc/pcie-designware.h
> @@ -190,8 +190,8 @@ struct pcie_port {
>  	int			msi_irq;
>  	struct irq_domain	*irq_domain;
>  	struct irq_domain	*msi_domain;
> -	u16			msi_msg;
>  	dma_addr_t		msi_data;
> +	struct page		*msi_page;
>  	struct irq_chip		*msi_irq_chip;
>  	u32			num_vectors;
>  	u32			irq_mask[MAX_MSI_CTRLS];
> -- 
> 2.36.1.124.g0e6072fb45-goog
>