Nouveau - May 2023 - [PATCH 1/4] x86: move a check out of pci_xen_swiotlb_init

Hi all,

this little series removes the last swiotlb API exposed to modules.

Diffstat:
 arch/x86/include/asm/xen/swiotlb-xen.h |    6 ------
 arch/x86/kernel/pci-dma.c              |   28 ++++------------------------
 drivers/gpu/drm/nouveau/nouveau_ttm.c  |   10 +++-------
 drivers/pci/xen-pcifront.c             |    6 ------
 kernel/dma/swiotlb.c                   |    1 -
 5 files changed, 7 insertions(+), 44 deletions(-)

Move the exact checks when to initialize the Xen swiotlb code out
of pci_xen_swiotlb_init and into the caller so that is uses readable
positive checks, rather than negative ones that will get even more
confusing with another addition.

Signed-off-by: Christoph Hellwig <hch at lst.de>
---
 arch/x86/kernel/pci-dma.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kernel/pci-dma.c b/arch/x86/kernel/pci-dma.c
index de6be0a3965ee4..f887b08ac5ffe4 100644
--- a/arch/x86/kernel/pci-dma.c
+++ b/arch/x86/kernel/pci-dma.c
@@ -74,8 +74,6 @@ static inline void __init pci_swiotlb_detect(void)
 #ifdef CONFIG_SWIOTLB_XEN
 static void __init pci_xen_swiotlb_init(void)
 {
-	if (!xen_initial_domain() && !x86_swiotlb_enable)
-		return;
 	x86_swiotlb_enable = true;
 	x86_swiotlb_flags |= SWIOTLB_ANY;
 	swiotlb_init_remap(true, x86_swiotlb_flags, xen_swiotlb_fixup);
@@ -113,7 +111,8 @@ static inline void __init pci_xen_swiotlb_init(void)
 void __init pci_iommu_alloc(void)
 {
 	if (xen_pv_domain()) {
-		pci_xen_swiotlb_init();
+		if (xen_initial_domain() || x86_swiotlb_enable)
+			pci_xen_swiotlb_init();
 		return;
 	}
 	pci_swiotlb_detect();
-- 
2.39.2

Remove the dangerous late initialization of xen-swiotlb in
pci_xen_swiotlb_init_late and instead just always initialize
xen-swiotlb in the boot code if CONFIG_XEN_PCIDEV_FRONTEND is enabled.

Signed-off-by: Christoph Hellwig <hch at lst.de>
---
 arch/x86/include/asm/xen/swiotlb-xen.h |  6 ------
 arch/x86/kernel/pci-dma.c              | 25 +++----------------------
 drivers/pci/xen-pcifront.c             |  6 ------
 3 files changed, 3 insertions(+), 34 deletions(-)

diff --git a/arch/x86/include/asm/xen/swiotlb-xen.h
b/arch/x86/include/asm/xen/swiotlb-xen.h
index 77a2d19cc9909e..abde0f44df57dc 100644
--- a/arch/x86/include/asm/xen/swiotlb-xen.h
+++ b/arch/x86/include/asm/xen/swiotlb-xen.h
@@ -2,12 +2,6 @@
 #ifndef _ASM_X86_SWIOTLB_XEN_H
 #define _ASM_X86_SWIOTLB_XEN_H
 
-#ifdef CONFIG_SWIOTLB_XEN
-extern int pci_xen_swiotlb_init_late(void);
-#else
-static inline int pci_xen_swiotlb_init_late(void) { return -ENXIO; }
-#endif
-
 int xen_swiotlb_fixup(void *buf, unsigned long nslabs);
 int xen_create_contiguous_region(phys_addr_t pstart, unsigned int order,
 				unsigned int address_bits,
diff --git a/arch/x86/kernel/pci-dma.c b/arch/x86/kernel/pci-dma.c
index f887b08ac5ffe4..c4a7ead9eb674e 100644
--- a/arch/x86/kernel/pci-dma.c
+++ b/arch/x86/kernel/pci-dma.c
@@ -81,27 +81,6 @@ static void __init pci_xen_swiotlb_init(void)
 	if (IS_ENABLED(CONFIG_PCI))
 		pci_request_acs();
 }
-
-int pci_xen_swiotlb_init_late(void)
-{
-	if (dma_ops == &xen_swiotlb_dma_ops)
-		return 0;
-
-	/* we can work with the default swiotlb */
-	if (!io_tlb_default_mem.nslabs) {
-		int rc = swiotlb_init_late(swiotlb_size_or_default(),
-					   GFP_KERNEL, xen_swiotlb_fixup);
-		if (rc < 0)
-			return rc;
-	}
-
-	/* XXX: this switches the dma ops under live devices! */
-	dma_ops = &xen_swiotlb_dma_ops;
-	if (IS_ENABLED(CONFIG_PCI))
-		pci_request_acs();
-	return 0;
-}
-EXPORT_SYMBOL_GPL(pci_xen_swiotlb_init_late);
 #else
 static inline void __init pci_xen_swiotlb_init(void)
 {
@@ -111,7 +90,9 @@ static inline void __init pci_xen_swiotlb_init(void)
 void __init pci_iommu_alloc(void)
 {
 	if (xen_pv_domain()) {
-		if (xen_initial_domain() || x86_swiotlb_enable)
+		if (xen_initial_domain() ||
+		    IS_ENABLED(CONFIG_XEN_PCIDEV_FRONTEND) ||
+		    x86_swiotlb_enable)
 			pci_xen_swiotlb_init();
 		return;
 	}
diff --git a/drivers/pci/xen-pcifront.c b/drivers/pci/xen-pcifront.c
index 83c0ab50676dff..11636634ae512f 100644
--- a/drivers/pci/xen-pcifront.c
+++ b/drivers/pci/xen-pcifront.c
@@ -22,7 +22,6 @@
 #include <linux/bitops.h>
 #include <linux/time.h>
 #include <linux/ktime.h>
-#include <linux/swiotlb.h>
 #include <xen/platform_pci.h>
 
 #include <asm/xen/swiotlb-xen.h>
@@ -669,11 +668,6 @@ static int pcifront_connect_and_init_dma(struct
pcifront_device *pdev)
 
 	spin_unlock(&pcifront_dev_lock);
 
-	if (!err && !is_swiotlb_active(&pdev->xdev->dev)) {
-		err = pci_xen_swiotlb_init_late();
-		if (err)
-			dev_err(&pdev->xdev->dev, "Could not setup SWIOTLB!\n");
-	}
 	return err;
 }
 
-- 
2.39.2

Drivers have no business looking into dma-mapping internals and check
what backend is used.  Unfortunstely the DRM core is still broken and
tries to do plain page allocations instead of using DMA API allocators
by default and uses various bandaids on when to use dma_alloc_coherent.

Switch nouveau to use the same (broken) scheme as amdgpu and radeon
to remove the last driver user of is_swiotlb_active.

Signed-off-by: Christoph Hellwig <hch at lst.de>
---
 drivers/gpu/drm/nouveau/nouveau_ttm.c | 10 +++-------
 1 file changed, 3 insertions(+), 7 deletions(-)

diff --git a/drivers/gpu/drm/nouveau/nouveau_ttm.c
b/drivers/gpu/drm/nouveau/nouveau_ttm.c
index 1469a88910e45d..486f39f31a38df 100644
--- a/drivers/gpu/drm/nouveau/nouveau_ttm.c
+++ b/drivers/gpu/drm/nouveau/nouveau_ttm.c
@@ -24,9 +24,9 @@
  */
 
 #include <linux/limits.h>
-#include <linux/swiotlb.h>
 
 #include <drm/ttm/ttm_range_manager.h>
+#include <drm/drm_cache.h>
 
 #include "nouveau_drv.h"
 #include "nouveau_gem.h"
@@ -265,7 +265,6 @@ nouveau_ttm_init(struct nouveau_drm *drm)
 	struct nvkm_pci *pci = device->pci;
 	struct nvif_mmu *mmu = &drm->client.mmu;
 	struct drm_device *dev = drm->dev;
-	bool need_swiotlb = false;
 	int typei, ret;
 
 	ret = nouveau_ttm_init_host(drm, 0);
@@ -300,13 +299,10 @@ nouveau_ttm_init(struct nouveau_drm *drm)
 		drm->agp.cma = pci->agp.cma;
 	}
 
-#if IS_ENABLED(CONFIG_SWIOTLB) && IS_ENABLED(CONFIG_X86)
-	need_swiotlb = is_swiotlb_active(dev->dev);
-#endif
-
 	ret = ttm_device_init(&drm->ttm.bdev, &nouveau_bo_driver,
drm->dev->dev,
 				  dev->anon_inode->i_mapping,
-				  dev->vma_offset_manager, need_swiotlb,
+				  dev->vma_offset_manager,
+				  drm_need_swiotlb(drm->client.mmu.dmabits),
 				  drm->client.mmu.dmabits <= 32);
 	if (ret) {
 		NV_ERROR(drm, "error initialising bo driver, %d\n", ret);
-- 
2.39.2

Drivers have no business looking at dma-mapping or swiotlb internals.

Signed-off-by: Christoph Hellwig <hch at lst.de>
---
 kernel/dma/swiotlb.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
index af2e304c672c43..9f1fd28264a067 100644
--- a/kernel/dma/swiotlb.c
+++ b/kernel/dma/swiotlb.c
@@ -921,7 +921,6 @@ bool is_swiotlb_active(struct device *dev)
 
 	return mem && mem->nslabs;
 }
-EXPORT_SYMBOL_GPL(is_swiotlb_active);
 
 #ifdef CONFIG_DEBUG_FS
 
-- 
2.39.2