swiotlb: Export swioltb_nr_tbl and utilize it as appropiate.

By default the io_tlb_nslabs is set to zero, and gets set to
whatever value is passed in via swiotlb_init_with_tbl function.
The default value passed in is 64MB. However, if the user provides
the 'swiotlb=<nslabs>' the default value is ignored and
the value provided by the user is used... Except when the SWIOTLB
is used under Xen - there the default value of 64MB is used and
the Xen-SWIOTLB has no mechanism to get the 'io_tlb_nslabs' filled
out by setup_io_tlb_npages functions. This patch provides a function
for the Xen-SWIOTLB to call to see if the io_tlb_nslabs is set
and if so use that value.

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

3 files changed, 15 insertions, 3 deletions

diff --git a/drivers/xen/swiotlb-xen.c b/drivers/xen/swiotlb-xen.c
index 54469c3eeacd..5ac3f4843f5c 100644
--- a/drivers/xen/swiotlb-xen.c
+++ b/drivers/xen/swiotlb-xen.c
@@ -147,9 +147,15 @@ void __init xen_swiotlb_init(int verbose)
 {
         unsigned long bytes;
         int rc;
-
-        xen_io_tlb_nslabs = (64 * 1024 * 1024 >> IO_TLB_SHIFT);
-        xen_io_tlb_nslabs = ALIGN(xen_io_tlb_nslabs, IO_TLB_SEGSIZE);
+        unsigned long nr_tbl;
+
+        nr_tbl = swioltb_nr_tbl();
+        if (nr_tbl)
+                xen_io_tlb_nslabs = nr_tbl;
+        else {
+                xen_io_tlb_nslabs = (64 * 1024 * 1024 >> IO_TLB_SHIFT);
+                xen_io_tlb_nslabs = ALIGN(xen_io_tlb_nslabs, IO_TLB_SEGSIZE);
+        }
 
         bytes = xen_io_tlb_nslabs << IO_TLB_SHIFT;
 
diff --git a/include/linux/swiotlb.h b/include/linux/swiotlb.h
index 8c0e349f4a6c..445702c60d04 100644
--- a/include/linux/swiotlb.h
+++ b/include/linux/swiotlb.h
@@ -24,6 +24,7 @@ extern int swiotlb_force;
 
 extern void swiotlb_init(int verbose);
 extern void swiotlb_init_with_tbl(char *tlb, unsigned long nslabs, int verbose);
+extern unsigned long swioltb_nr_tbl(void);
 
 /*
  * Enumeration for sync targets
diff --git a/lib/swiotlb.c b/lib/swiotlb.c
index 93ca08b8a451..99093b396145 100644
--- a/lib/swiotlb.c
+++ b/lib/swiotlb.c
@@ -110,6 +110,11 @@ setup_io_tlb_npages(char *str)
 __setup("swiotlb=", setup_io_tlb_npages);
 /* make io_tlb_overflow tunable too? */
 
+unsigned long swioltb_nr_tbl(void)
+{
+        return io_tlb_nslabs;
+}
+
 /* Note that this doesn't work with highmem page */
 static dma_addr_t swiotlb_virt_to_bus(struct device *hwdev,
                                       volatile void *address)