unexport swiotlb_active v2

unexport swiotlb_active v2

[Christoph Hellwig]

Hi all,

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

Changes since v1:
 - add a patch from Juergen to export if the e820 table indicates Xen PV
   PCI is enabled
 - slightly reorganize the logic to check if swiotlb is needed for
   Xen/x86
 - drop the already merged nouveau patch

Diffstat:
 arch/x86/include/asm/xen/swiotlb-xen.h |    6 ------
 arch/x86/kernel/pci-dma.c              |   29 +++++++----------------------
 arch/x86/xen/setup.c                   |    6 ++++++
 drivers/pci/xen-pcifront.c             |    6 ------
 include/xen/xen.h                      |    6 ++++++
 kernel/dma/swiotlb.c                   |    1 -
 6 files changed, 19 insertions(+), 35 deletions(-)

[PATCH 1/3] xen/pci: add flag for PCI passthrough being possible

[Christoph Hellwig]

From: Juergen Gross <jgross@suse.com>

When running as a Xen PV guests passed through PCI devices only have a
chance to work if the Xen supplied memory map has some PCI space
reserved.

Add a flag xen_pv_pci_possible which will be set in early boot in case
the memory map has at least one area with the type E820_TYPE_RESERVED.

Signed-off-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 arch/x86/xen/setup.c | 6 ++++++
 include/xen/xen.h    | 6 ++++++
 2 files changed, 12 insertions(+)

diff --git a/arch/x86/xen/setup.c b/arch/x86/xen/setup.c
index c2be3efb2ba0fa..716f76c4141651 100644
--- a/arch/x86/xen/setup.c
+++ b/arch/x86/xen/setup.c
@@ -43,6 +43,9 @@ struct xen_memory_region xen_extra_mem[XEN_EXTRA_MEM_MAX_REGIONS] __initdata;
 /* Number of pages released from the initial allocation. */
 unsigned long xen_released_pages;
 
+/* Memory map would allow PCI passthrough. */
+bool xen_pv_pci_possible;
+
 /* E820 map used during setting up memory. */
 static struct e820_table xen_e820_table __initdata;
 
@@ -804,6 +807,9 @@ char * __init xen_memory_setup(void)
 		chunk_size = size;
 		type = xen_e820_table.entries[i].type;
 
+		if (type == E820_TYPE_RESERVED)
+			xen_pv_pci_possible = true;
+
 		if (type == E820_TYPE_RAM) {
 			if (addr < mem_end) {
 				chunk_size = min(size, mem_end - addr);
diff --git a/include/xen/xen.h b/include/xen/xen.h
index 0efeb652f9b8fb..5eb0a974a11e7e 100644
--- a/include/xen/xen.h
+++ b/include/xen/xen.h
@@ -29,6 +29,12 @@ extern bool xen_pvh;
 
 extern uint32_t xen_start_flags;
 
+#ifdef CONFIG_XEN_PV
+extern bool xen_pv_pci_possible;
+#else
+#define xen_pv_pci_possible	0
+#endif
+
 #include <xen/interface/hvm/start_info.h>
 extern struct hvm_start_info pvh_start_info;
 
-- 
2.39.2

[PATCH 2/3] x86: always initialize xen-swiotlb when xen-pcifront is enabling

[Christoph Hellwig]

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 and Xen PV PCI is possible.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 arch/x86/include/asm/xen/swiotlb-xen.h |  6 ------
 arch/x86/kernel/pci-dma.c              | 29 +++++++-------------------
 drivers/pci/xen-pcifront.c             |  6 ------
 3 files changed, 7 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 de6be0a3965ee4..f323d83e40a70b 100644
--- a/arch/x86/kernel/pci-dma.c
+++ b/arch/x86/kernel/pci-dma.c
@@ -72,9 +72,15 @@ static inline void __init pci_swiotlb_detect(void)
 #endif /* CONFIG_SWIOTLB */
 
 #ifdef CONFIG_SWIOTLB_XEN
+static bool xen_swiotlb_enabled(void)
+{
+	return xen_initial_domain() || x86_swiotlb_enable ||
+		(IS_ENABLED(CONFIG_XEN_PCIDEV_FRONTEND) && xen_pv_pci_possible);
+}
+
 static void __init pci_xen_swiotlb_init(void)
 {
-	if (!xen_initial_domain() && !x86_swiotlb_enable)
+	if (!xen_swiotlb_enabled())
 		return;
 	x86_swiotlb_enable = true;
 	x86_swiotlb_flags |= SWIOTLB_ANY;
@@ -83,27 +89,6 @@ 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)
 {
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

Re: [PATCH 2/3] x86: always initialize xen-swiotlb when xen-pcifront is enabling

[Juergen Gross]

[-- Attachment #1.1.1: Type: text/plain, Size: 391 bytes --]

On 12.06.23 16:25, Christoph Hellwig wrote:
> 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 and Xen PV PCI is possible.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>

Reviewed-by: Juergen Gross <jgross@suse.com>


Juergen


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[PATCH 3/3] swiotlb: unexport is_swiotlb_active

[Christoph Hellwig]

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

Signed-off-by: Christoph Hellwig <hch@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 775f7bb10ab184..1891faa3a6952e 100644
--- a/kernel/dma/swiotlb.c
+++ b/kernel/dma/swiotlb.c
@@ -932,7 +932,6 @@ bool is_swiotlb_active(struct device *dev)
 
 	return mem && mem->nslabs;
 }
-EXPORT_SYMBOL_GPL(is_swiotlb_active);
 
 #ifdef CONFIG_DEBUG_FS
 
-- 
2.39.2

Re: [PATCH 3/3] swiotlb: unexport is_swiotlb_active

[Juergen Gross]

[-- Attachment #1.1.1: Type: text/plain, Size: 234 bytes --]

On 12.06.23 16:25, Christoph Hellwig wrote:
> Drivers have no business looking at dma-mapping or swiotlb internals.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>

Reviewed-by: Juergen Gross <jgross@suse.com>


Juergen


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Re: unexport swiotlb_active v2

[Christoph Hellwig]

Any comments?  I'd really like to finish this off this merge window..

Re: unexport swiotlb_active v2

[Petr Tesařík]

On Mon, 19 Jun 2023 11:19:41 +0200
Christoph Hellwig <hch@lst.de> wrote:

> Any comments?  I'd really like to finish this off this merge window..

Let me second this request. My dynamic SWIOTLB patch series also has a
dependence on this.

Petr T