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

[Will McVicker <willmcvicker@google.com>]

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>
---
 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