Re: [PATCH v13 01/12] swiotlb: Refactor swiotlb init functions

On Fri, Jun 18, 2021 at 7:30 AM Stefano Stabellini
[off-list ref] wrote:

On Thu, 17 Jun 2021, Claire Chang wrote:

quoted

Add a new function, swiotlb_init_io_tlb_mem, for the io_tlb_mem struct
initialization to make the code reusable.

Signed-off-by: Claire Chang <redacted>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Tested-by: Stefano Stabellini <sstabellini@kernel.org>
Tested-by: Will Deacon <will@kernel.org>
---
 kernel/dma/swiotlb.c | 50 ++++++++++++++++++++++----------------------
 1 file changed, 25 insertions(+), 25 deletions(-)

diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
index 52e2ac526757..47bb2a766798 100644
--- a/kernel/dma/swiotlb.c
+++ b/kernel/dma/swiotlb.c

@@ -168,9 +168,28 @@ void __init swiotlb_update_mem_attributes(void)
      memset(vaddr, 0, bytes);
 }

-int __init swiotlb_init_with_tbl(char *tlb, unsigned long nslabs, int verbose)
+static void swiotlb_init_io_tlb_mem(struct io_tlb_mem *mem, phys_addr_t start,
+                                 unsigned long nslabs, bool late_alloc)
 {
+     void *vaddr = phys_to_virt(start);
      unsigned long bytes = nslabs << IO_TLB_SHIFT, i;
+
+     mem->nslabs = nslabs;
+     mem->start = start;
+     mem->end = mem->start + bytes;
+     mem->index = 0;
+     mem->late_alloc = late_alloc;
+     spin_lock_init(&mem->lock);
+     for (i = 0; i < mem->nslabs; i++) {
+             mem->slots[i].list = IO_TLB_SEGSIZE - io_tlb_offset(i);
+             mem->slots[i].orig_addr = INVALID_PHYS_ADDR;
+             mem->slots[i].alloc_size = 0;
+     }
+     memset(vaddr, 0, bytes);
+}
+
+int __init swiotlb_init_with_tbl(char *tlb, unsigned long nslabs, int verbose)
+{
      struct io_tlb_mem *mem;
      size_t alloc_size;

@@ -186,16 +205,8 @@ int __init swiotlb_init_with_tbl(char *tlb, unsigned long nslabs, int verbose)
      if (!mem)
              panic("%s: Failed to allocate %zu bytes align=0x%lx\n",
                    __func__, alloc_size, PAGE_SIZE);
-     mem->nslabs = nslabs;
-     mem->start = __pa(tlb);
-     mem->end = mem->start + bytes;
-     mem->index = 0;
-     spin_lock_init(&mem->lock);
-     for (i = 0; i < mem->nslabs; i++) {
-             mem->slots[i].list = IO_TLB_SEGSIZE - io_tlb_offset(i);
-             mem->slots[i].orig_addr = INVALID_PHYS_ADDR;
-             mem->slots[i].alloc_size = 0;
-     }
+
+     swiotlb_init_io_tlb_mem(mem, __pa(tlb), nslabs, false);

      io_tlb_default_mem = mem;
      if (verbose)

@@ -282,8 +293,8 @@ swiotlb_late_init_with_default_size(size_t default_size)
 int
 swiotlb_late_init_with_tbl(char *tlb, unsigned long nslabs)
 {
-     unsigned long bytes = nslabs << IO_TLB_SHIFT, i;
      struct io_tlb_mem *mem;
+     unsigned long bytes = nslabs << IO_TLB_SHIFT;

      if (swiotlb_force == SWIOTLB_NO_FORCE)
              return 0;

@@ -297,20 +308,9 @@ swiotlb_late_init_with_tbl(char *tlb, unsigned long nslabs)
      if (!mem)
              return -ENOMEM;

-     mem->nslabs = nslabs;
-     mem->start = virt_to_phys(tlb);
-     mem->end = mem->start + bytes;
-     mem->index = 0;
-     mem->late_alloc = 1;
-     spin_lock_init(&mem->lock);
-     for (i = 0; i < mem->nslabs; i++) {
-             mem->slots[i].list = IO_TLB_SEGSIZE - io_tlb_offset(i);
-             mem->slots[i].orig_addr = INVALID_PHYS_ADDR;
-             mem->slots[i].alloc_size = 0;
-     }
-
+     memset(mem, 0, sizeof(*mem));
+     swiotlb_init_io_tlb_mem(mem, virt_to_phys(tlb), nslabs, true);
      set_memory_decrypted((unsigned long)tlb, bytes >> PAGE_SHIFT);
-     memset(tlb, 0, bytes);

This is good for swiotlb_late_init_with_tbl. However I have just noticed
that mem could also be allocated from swiotlb_init_with_tbl, in which
case the zeroing is missing. I think we need another memset in
swiotlb_init_with_tbl as well. Or maybe it could be better to have a
single memset at the beginning of swiotlb_init_io_tlb_mem instead. Up to
you.

swiotlb_init_with_tbl uses memblock_alloc to allocate the io_tlb_mem
and memblock_alloc[1] will do memset in memblock_alloc_try_nid[2], so
swiotlb_init_with_tbl is also good.
I'm happy to add the memset in swiotlb_init_io_tlb_mem if you think
it's clearer and safer.

[1] https://elixir.bootlin.com/linux/v5.13-rc6/source/include/linux/memblock.h#L407
[2] https://elixir.bootlin.com/linux/v5.13-rc6/source/mm/memblock.c#L1555