linux-kernel - [PATCH v1 07/10] powerpc/pseries/iommu: Allow DDW windows starting at 0x00

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Date:   Mon, 17 Aug 2020 20:40:30 -0300
From:   Leonardo Bras <leobras.c@...il.com>
To:     Michael Ellerman <mpe@...erman.id.au>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Alexey Kardashevskiy <aik@...abs.ru>,
        Christophe Leroy <christophe.leroy@....fr>,
        Leonardo Bras <leobras.c@...il.com>,
        Joel Stanley <joel@....id.au>,
        Thiago Jung Bauermann <bauerman@...ux.ibm.com>,
        Ram Pai <linuxram@...ibm.com>,
        Brian King <brking@...ux.vnet.ibm.com>,
        Murilo Fossa Vicentini <muvic@...ux.ibm.com>,
        David Dai <zdai@...ux.vnet.ibm.com>
Cc:     linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: [PATCH v1 07/10] powerpc/pseries/iommu: Allow DDW windows starting at 0x00

enable_ddw() currently returns the address of the DMA window, which is
considered invalid if has the value 0x00.

Also, it only considers valid an address returned from find_existing_ddw
if it's not 0x00.

Changing this behavior makes sense, given the users of enable_ddw() only
need to know if direct mapping is possible. It can also allow a DMA window
starting at 0x00 to be used.

This will be helpful for using a DDW with indirect mapping, as the window
address will be different than 0x00, but it will not map the whole
partition.

Signed-off-by: Leonardo Bras <leobras.c@...il.com>
---
 arch/powerpc/platforms/pseries/iommu.c | 30 ++++++++++++--------------
 1 file changed, 14 insertions(+), 16 deletions(-)

diff --git a/arch/powerpc/platforms/pseries/iommu.c b/arch/powerpc/platforms/pseries/iommu.c
index fcdefcc0f365..4031127c9537 100644
--- a/arch/powerpc/platforms/pseries/iommu.c
+++ b/arch/powerpc/platforms/pseries/iommu.c
@@ -852,24 +852,25 @@ static void remove_ddw(struct device_node *np, bool remove_prop)
 			np, ret);
 }
 
-static u64 find_existing_ddw(struct device_node *pdn)
+static bool find_existing_ddw(struct device_node *pdn, u64 *dma_addr)
 {
 	struct direct_window *window;
 	const struct dynamic_dma_window_prop *direct64;
-	u64 dma_addr = 0;
+	bool found = false;
 
 	spin_lock(&direct_window_list_lock);
 	/* check if we already created a window and dupe that config if so */
 	list_for_each_entry(window, &direct_window_list, list) {
 		if (window->device == pdn) {
 			direct64 = window->prop;
-			dma_addr = be64_to_cpu(direct64->dma_base);
+			*dma_addr = be64_to_cpu(direct64->dma_base);
+			found = true;
 			break;
 		}
 	}
 	spin_unlock(&direct_window_list_lock);
 
-	return dma_addr;
+	return found;
 }
 
 static struct direct_window *ddw_list_add(struct device_node *pdn,
@@ -1131,15 +1132,15 @@ static void reset_dma_window(struct pci_dev *dev, struct device_node *par_dn)
  * pdn: the parent pe node with the ibm,dma_window property
  * Future: also check if we can remap the base window for our base page size
  *
- * returns the dma offset for use by the direct mapped DMA code.
+ * returns true if can map all pages (direct mapping), false otherwise..
  */
-static u64 enable_ddw(struct pci_dev *dev, struct device_node *pdn)
+static bool enable_ddw(struct pci_dev *dev, struct device_node *pdn)
 {
 	int len, ret;
 	struct ddw_query_response query;
 	struct ddw_create_response create;
 	int page_shift;
-	u64 dma_addr, max_addr;
+	u64 max_addr;
 	struct device_node *dn;
 	u32 ddw_avail[DDW_APPLICABLE_SIZE];
 	struct direct_window *window;
@@ -1150,8 +1151,7 @@ static u64 enable_ddw(struct pci_dev *dev, struct device_node *pdn)
 
 	mutex_lock(&direct_window_init_mutex);
 
-	dma_addr = find_existing_ddw(pdn);
-	if (dma_addr != 0)
+	if (find_existing_ddw(pdn, &dev->dev.archdata.dma_offset))
 		goto out_unlock;
 
 	/*
@@ -1292,7 +1292,7 @@ static u64 enable_ddw(struct pci_dev *dev, struct device_node *pdn)
 		goto out_free_window;
 	}
 
-	dma_addr = be64_to_cpu(ddwprop->dma_base);
+	dev->dev.archdata.dma_offset = be64_to_cpu(ddwprop->dma_base);
 	goto out_unlock;
 
 out_free_window:
@@ -1309,6 +1309,7 @@ static u64 enable_ddw(struct pci_dev *dev, struct device_node *pdn)
 	kfree(win64->name);
 	kfree(win64->value);
 	kfree(win64);
+	win64 = NULL;
 
 out_failed:
 	if (default_win_removed)
@@ -1322,7 +1323,7 @@ static u64 enable_ddw(struct pci_dev *dev, struct device_node *pdn)
 
 out_unlock:
 	mutex_unlock(&direct_window_init_mutex);
-	return dma_addr;
+	return win64;
 }
 
 static void pci_dma_dev_setup_pSeriesLP(struct pci_dev *dev)
@@ -1401,11 +1402,8 @@ static bool iommu_bypass_supported_pSeriesLP(struct pci_dev *pdev, u64 dma_mask)
 			break;
 	}
 
-	if (pdn && PCI_DN(pdn)) {
-		pdev->dev.archdata.dma_offset = enable_ddw(pdev, pdn);
-		if (pdev->dev.archdata.dma_offset)
-			return true;
-	}
+	if (pdn && PCI_DN(pdn))
+		return enable_ddw(pdev, pdn);
 
 	return false;
 }
-- 
2.25.4