xen/swiotlb: Use the swiotlb_late_init_with_tbl to init Xen-SWIOTLB late when PV PCI is used.

With this patch we provide the functionality to initialize the
Xen-SWIOTLB late in the bootup cycle - specifically for
Xen PCI-frontend. We still will work if the user had
supplied 'iommu=soft' on the Linux command line.

Note: We cannot depend on after_bootmem to automatically
determine whether this is early or not. This is because
when PCI IOMMUs are initialized it is after after_bootmem but
before a lot of "other" subsystems are initialized.

CC: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
[v1: Fix smatch warnings]
[v2: Added check for xen_swiotlb]
[v3: Rebased with new xen-swiotlb changes]
[v4: squashed xen/swiotlb: Depending on after_bootmem is not correct in]
Reviewed-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

4 files changed, 63 insertions, 13 deletions

diff --git a/arch/x86/include/asm/xen/swiotlb-xen.h b/arch/x86/include/asm/xen/swiotlb-xen.h
index 1be1ab7d6a41..ee52fcac6f72 100644
--- a/arch/x86/include/asm/xen/swiotlb-xen.h
+++ b/arch/x86/include/asm/xen/swiotlb-xen.h
@@ -5,10 +5,12 @@
 extern int xen_swiotlb;
 extern int __init pci_xen_swiotlb_detect(void);
 extern void __init pci_xen_swiotlb_init(void);
+extern int pci_xen_swiotlb_init_late(void);
 #else
 #define xen_swiotlb (0)
 static inline int __init pci_xen_swiotlb_detect(void) { return 0; }
 static inline void __init pci_xen_swiotlb_init(void) { }
+static inline int pci_xen_swiotlb_init_late(void) { return -ENXIO; }
 #endif
 
 #endif /* _ASM_X86_SWIOTLB_XEN_H */
diff --git a/arch/x86/xen/pci-swiotlb-xen.c b/arch/x86/xen/pci-swiotlb-xen.c
index 1c1722761eec..b152640d8388 100644
--- a/arch/x86/xen/pci-swiotlb-xen.c
+++ b/arch/x86/xen/pci-swiotlb-xen.c
@@ -12,7 +12,7 @@
 #include <asm/iommu.h>
 #include <asm/dma.h>
 #endif
-
+#include <linux/export.h>
 int xen_swiotlb __read_mostly;
 
 static struct dma_map_ops xen_swiotlb_dma_ops = {
@@ -69,13 +69,33 @@ int __init pci_xen_swiotlb_detect(void)
 void __init pci_xen_swiotlb_init(void)
 {
         if (xen_swiotlb) {
-                xen_swiotlb_init(1);
+                xen_swiotlb_init(1, true /* early */);
                 dma_ops = &xen_swiotlb_dma_ops;
 
                 /* Make sure ACS will be enabled */
                 pci_request_acs();
         }
 }
+
+int pci_xen_swiotlb_init_late(void)
+{
+        int rc;
+
+        if (xen_swiotlb)
+                return 0;
+
+        rc = xen_swiotlb_init(1, false /* late */);
+        if (rc)
+                return rc;
+
+        dma_ops = &xen_swiotlb_dma_ops;
+        /* Make sure ACS will be enabled */
+        pci_request_acs();
+
+        return 0;
+}
+EXPORT_SYMBOL_GPL(pci_xen_swiotlb_init_late);
+
 IOMMU_INIT_FINISH(pci_xen_swiotlb_detect,
                   0,
                   pci_xen_swiotlb_init,
diff --git a/drivers/xen/swiotlb-xen.c b/drivers/xen/swiotlb-xen.c
index 701b1035fa6f..7461edb5118e 100644
--- a/drivers/xen/swiotlb-xen.c
+++ b/drivers/xen/swiotlb-xen.c
@@ -176,9 +176,9 @@ static const char *xen_swiotlb_error(enum xen_swiotlb_err err)
         }
         return "";
 }
-void __init xen_swiotlb_init(int verbose)
+int __ref xen_swiotlb_init(int verbose, bool early)
 {
-        unsigned long bytes;
+        unsigned long bytes, order;
         int rc = -ENOMEM;
         enum xen_swiotlb_err m_ret = XEN_SWIOTLB_UNKNOWN;
         unsigned int repeat = 3;
@@ -186,10 +186,28 @@ void __init xen_swiotlb_init(int verbose)
         xen_io_tlb_nslabs = swiotlb_nr_tbl();
 retry:
         bytes = xen_set_nslabs(xen_io_tlb_nslabs);
+        order = get_order(xen_io_tlb_nslabs << IO_TLB_SHIFT);
         /*
          * Get IO TLB memory from any location.
          */
-        xen_io_tlb_start = alloc_bootmem_pages(PAGE_ALIGN(bytes));
+        if (early)
+                xen_io_tlb_start = alloc_bootmem_pages(PAGE_ALIGN(bytes));
+        else {
+#define SLABS_PER_PAGE (1 << (PAGE_SHIFT - IO_TLB_SHIFT))
+#define IO_TLB_MIN_SLABS ((1<<20) >> IO_TLB_SHIFT)
+                while ((SLABS_PER_PAGE << order) > IO_TLB_MIN_SLABS) {
+                        xen_io_tlb_start = (void *)__get_free_pages(__GFP_NOWARN, order);
+                        if (xen_io_tlb_start)
+                                break;
+                        order--;
+                }
+                if (order != get_order(bytes)) {
+                        pr_warn("Warning: only able to allocate %ld MB "
+                                "for software IO TLB\n", (PAGE_SIZE << order) >> 20);
+                        xen_io_tlb_nslabs = SLABS_PER_PAGE << order;
+                        bytes = xen_io_tlb_nslabs << IO_TLB_SHIFT;
+                }
+        }
         if (!xen_io_tlb_start) {
                 m_ret = XEN_SWIOTLB_ENOMEM;
                 goto error;
@@ -202,14 +220,21 @@ retry:
                                bytes,
                                xen_io_tlb_nslabs);
         if (rc) {
-                free_bootmem(__pa(xen_io_tlb_start), PAGE_ALIGN(bytes));
+                if (early)
+                        free_bootmem(__pa(xen_io_tlb_start), PAGE_ALIGN(bytes));
+                else {
+                        free_pages((unsigned long)xen_io_tlb_start, order);
+                        xen_io_tlb_start = NULL;
+                }
                 m_ret = XEN_SWIOTLB_EFIXUP;
                 goto error;
         }
         start_dma_addr = xen_virt_to_bus(xen_io_tlb_start);
-        swiotlb_init_with_tbl(xen_io_tlb_start, xen_io_tlb_nslabs, verbose);
-
-        return;
+        if (early)
+                swiotlb_init_with_tbl(xen_io_tlb_start, xen_io_tlb_nslabs, verbose);
+        else
+                rc = swiotlb_late_init_with_tbl(xen_io_tlb_start, xen_io_tlb_nslabs);
+        return rc;
 error:
         if (repeat--) {
                 xen_io_tlb_nslabs = max(1024UL, /* Min is 2MB */
@@ -218,10 +243,13 @@ error:
                       (xen_io_tlb_nslabs << IO_TLB_SHIFT) >> 20);
                 goto retry;
         }
-        xen_raw_printk("%s (rc:%d)", xen_swiotlb_error(m_ret), rc);
-        panic("%s (rc:%d)", xen_swiotlb_error(m_ret), rc);
+        pr_err("%s (rc:%d)", xen_swiotlb_error(m_ret), rc);
+        if (early)
+                panic("%s (rc:%d)", xen_swiotlb_error(m_ret), rc);
+        else
+                free_pages((unsigned long)xen_io_tlb_start, order);
+        return rc;
 }
-
 void *
 xen_swiotlb_alloc_coherent(struct device *hwdev, size_t size,
                            dma_addr_t *dma_handle, gfp_t flags,
diff --git a/include/xen/swiotlb-xen.h b/include/xen/swiotlb-xen.h
index 4f4d449f00f6..289ee509bda9 100644
--- a/include/xen/swiotlb-xen.h
+++ b/include/xen/swiotlb-xen.h
@@ -3,7 +3,7 @@
 
 #include <linux/swiotlb.h>
 
-extern void xen_swiotlb_init(int verbose);
+extern int xen_swiotlb_init(int verbose, bool early);
 
 extern void
 *xen_swiotlb_alloc_coherent(struct device *hwdev, size_t size,