[Xen-devel] [PATCH 35/35] x86: Don't panic if can not alloc buffer for swiotlb

[Yinghai Lu <yinghai@xxxxxxxxxx>]

Normal boot path on system with iommu support:
swiotlb buffer will be allocated early at first and then try to initialize
iommu, if iommu for intel or AMD could setup properly, swiotlb buffer
will be freed.

The early allocating is with bootmem, and could panic when we try to use
kdump with buffer above 4G only, or with memmap to limit mem under 4G.
for example: memmap=4095M$1M to remove memory under 4G.

According to Eric, add _nopanic version and no_iotlb_memory to fail
map single later if swiotlb is still needed.

-v2: don't pass nopanic, and use -ENOMEM return value according to Eric.
     panic early instead of using swiotlb_full to panic...according to 
Eric/Konrad.
-v3: make swiotlb_init to be notpanic, but will affect:
     arm64, ia64, powerpc, tile, unicore32, x86.
-v4: cleanup swiotlb_init by removing swiotlb_init_with_default_size.

Suggested-by: Eric W. Biederman <ebiederm@xxxxxxxxxxxx>
Signed-off-by: Yinghai Lu <yinghai@xxxxxxxxxx>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
Cc: Joerg Roedel <joro@xxxxxxxxxx>
Cc: Ralf Baechle <ralf@xxxxxxxxxxxxxx>
Cc: Jeremy Fitzhardinge <jeremy@xxxxxxxx>
Cc: Kyungmin Park <kyungmin.park@xxxxxxxxxxx>
Cc: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>
Cc: Arnd Bergmann <arnd@xxxxxxxx>
Cc: Andrzej Pietrasiewicz <andrzej.p@xxxxxxxxxxx>
Cc: linux-mips@xxxxxxxxxxxxxx
Cc: xen-devel@xxxxxxxxxxxxxxxxxxx
Cc: virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx
Cc: Shuah Khan <shuahkhan@xxxxxxxxx>
---
 arch/mips/cavium-octeon/dma-octeon.c |    3 ++-
 drivers/xen/swiotlb-xen.c            |    4 ++-
 include/linux/swiotlb.h              |    2 +-
 lib/swiotlb.c                        |   47 +++++++++++++++++++++-------------
 4 files changed, 35 insertions(+), 21 deletions(-)

diff --git a/arch/mips/cavium-octeon/dma-octeon.c 
b/arch/mips/cavium-octeon/dma-octeon.c
index 41dd0088..02f2444 100644
--- a/arch/mips/cavium-octeon/dma-octeon.c
+++ b/arch/mips/cavium-octeon/dma-octeon.c
@@ -317,7 +317,8 @@ void __init plat_swiotlb_setup(void)
 
        octeon_swiotlb = alloc_bootmem_low_pages(swiotlbsize);
 
-       swiotlb_init_with_tbl(octeon_swiotlb, swiotlb_nslabs, 1);
+       if (swiotlb_init_with_tbl(octeon_swiotlb, swiotlb_nslabs, 1) == -ENOMEM)
+               panic("Cannot allocate SWIOTLB buffer");
 
        mips_dma_map_ops = &octeon_linear_dma_map_ops.dma_map_ops;
 }
diff --git a/drivers/xen/swiotlb-xen.c b/drivers/xen/swiotlb-xen.c
index af47e75..1d94316 100644
--- a/drivers/xen/swiotlb-xen.c
+++ b/drivers/xen/swiotlb-xen.c
@@ -231,7 +231,9 @@ retry:
        }
        start_dma_addr = xen_virt_to_bus(xen_io_tlb_start);
        if (early) {
-               swiotlb_init_with_tbl(xen_io_tlb_start, xen_io_tlb_nslabs, 
verbose);
+               if (swiotlb_init_with_tbl(xen_io_tlb_start, xen_io_tlb_nslabs,
+                        verbose))
+                       panic("Cannot allocate SWIOTLB buffer");
                rc = 0;
        } else
                rc = swiotlb_late_init_with_tbl(xen_io_tlb_start, 
xen_io_tlb_nslabs);
diff --git a/include/linux/swiotlb.h b/include/linux/swiotlb.h
index 071d62c..2de42f9 100644
--- a/include/linux/swiotlb.h
+++ b/include/linux/swiotlb.h
@@ -23,7 +23,7 @@ extern int swiotlb_force;
 #define IO_TLB_SHIFT 11
 
 extern void swiotlb_init(int verbose);
-extern void swiotlb_init_with_tbl(char *tlb, unsigned long nslabs, int 
verbose);
+int swiotlb_init_with_tbl(char *tlb, unsigned long nslabs, int verbose);
 extern unsigned long swiotlb_nr_tbl(void);
 extern int swiotlb_late_init_with_tbl(char *tlb, unsigned long nslabs);
 
diff --git a/lib/swiotlb.c b/lib/swiotlb.c
index 196b069..bfe02b8 100644
--- a/lib/swiotlb.c
+++ b/lib/swiotlb.c
@@ -122,11 +122,18 @@ static dma_addr_t swiotlb_virt_to_bus(struct device 
*hwdev,
        return phys_to_dma(hwdev, virt_to_phys(address));
 }
 
+static bool no_iotlb_memory;
+
 void swiotlb_print_info(void)
 {
        unsigned long bytes = io_tlb_nslabs << IO_TLB_SHIFT;
        unsigned char *vstart, *vend;
 
+       if (no_iotlb_memory) {
+               pr_warn("software IO TLB: No low mem\n");
+               return;
+       }
+
        vstart = phys_to_virt(io_tlb_start);
        vend = phys_to_virt(io_tlb_end);
 
@@ -136,7 +143,7 @@ void swiotlb_print_info(void)
               bytes >> 20, vstart, vend - 1);
 }
 
-void __init swiotlb_init_with_tbl(char *tlb, unsigned long nslabs, int verbose)
+int __init swiotlb_init_with_tbl(char *tlb, unsigned long nslabs, int verbose)
 {
        void *v_overflow_buffer;
        unsigned long i, bytes;
@@ -150,9 +157,10 @@ void __init swiotlb_init_with_tbl(char *tlb, unsigned long 
nslabs, int verbose)
        /*
         * Get the overflow emergency buffer
         */
-       v_overflow_buffer = 
alloc_bootmem_low_pages(PAGE_ALIGN(io_tlb_overflow));
+       v_overflow_buffer = alloc_bootmem_low_pages_nopanic(
+                                               PAGE_ALIGN(io_tlb_overflow));
        if (!v_overflow_buffer)
-               panic("Cannot allocate SWIOTLB overflow buffer!\n");
+               return -ENOMEM;
 
        io_tlb_overflow_buffer = __pa(v_overflow_buffer);
 
@@ -169,15 +177,19 @@ void __init swiotlb_init_with_tbl(char *tlb, unsigned 
long nslabs, int verbose)
 
        if (verbose)
                swiotlb_print_info();
+
+       return 0;
 }
 
 /*
  * Statically reserve bounce buffer space and initialize bounce buffer data
  * structures for the software IO TLB used to implement the DMA API.
  */
-static void __init
-swiotlb_init_with_default_size(size_t default_size, int verbose)
+void  __init
+swiotlb_init(int verbose)
 {
+       /* default to 64MB */
+       size_t default_size = 64UL<<20;
        unsigned char *vstart;
        unsigned long bytes;
 
@@ -188,20 +200,16 @@ swiotlb_init_with_default_size(size_t default_size, int 
verbose)
 
        bytes = io_tlb_nslabs << IO_TLB_SHIFT;
 
-       /*
-        * Get IO TLB memory from the low pages
-        */
-       vstart = alloc_bootmem_low_pages(PAGE_ALIGN(bytes));
-       if (!vstart)
-               panic("Cannot allocate SWIOTLB buffer");
-
-       swiotlb_init_with_tbl(vstart, io_tlb_nslabs, verbose);
-}
+       /* Get IO TLB memory from the low pages */
+       vstart = alloc_bootmem_low_pages_nopanic(PAGE_ALIGN(bytes));
+       if (vstart && !swiotlb_init_with_tbl(vstart, io_tlb_nslabs, verbose))
+               return;
 
-void __init
-swiotlb_init(int verbose)
-{
-       swiotlb_init_with_default_size(64 * (1<<20), verbose);  /* default to 
64MB */
+       if (io_tlb_start)
+               free_bootmem(io_tlb_start,
+                                PAGE_ALIGN(io_tlb_nslabs << IO_TLB_SHIFT));
+       pr_warn("Cannot allocate SWIOTLB buffer");
+       no_iotlb_memory = true;
 }
 
 /*
@@ -405,6 +413,9 @@ phys_addr_t swiotlb_tbl_map_single(struct device *hwdev,
        unsigned long offset_slots;
        unsigned long max_slots;
 
+       if (no_iotlb_memory)
+               panic("Can not allocate SWIOTLB buffer earlier and can't now 
provide you with the DMA bounce buffer");
+
        mask = dma_get_seg_boundary(hwdev);
 
        tbl_dma_addr &= mask;
-- 
1.7.10.4


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