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Date: Fri, 22 Jul 2022 04:03:21 +0000
From: "Michael Kelley (LINUX)" <mikelley@...rosoft.com>
To: Tianyu Lan <ltykernel@...il.com>,
"hch@...radead.org" <hch@...radead.org>,
"m.szyprowski@...sung.com" <m.szyprowski@...sung.com>,
"robin.murphy@....com" <robin.murphy@....com>
CC: Tianyu Lan <Tianyu.Lan@...rosoft.com>,
"iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>
Subject: RE: [PATCH] swiotlb: Clean up some coding style and minor issues
From: Tianyu Lan <ltykernel@...il.com> Sent: Thursday, July 21, 2022 8:39 PM
>
> - Fix the used field of struct io_tlb_area wasn't initialized
> - Set area number to be 0 if input area number parameter is 0
> - Use array_size() to calculate io_tlb_area array size
> - Fix error handle of io_tlb_used debugfs node and introduce
> fops_io_tlb_used attribute
> - Make parameters of swiotlb_do_find_slots() more reasonable
>
I think you missed one of the bugs I pointed out in my previous
comments. In the function rmem_swiotlb_device_init(), the two
calls to kfree() in the error path are in the wrong order. It's a
path that will probably never happen, but it still should be fixed.
The other fixes look good to me.
Michael
> Fixes: 26ffb91fa5e0 ("swiotlb: split up the global swiotlb lock")
> Signed-off-by: Tianyu Lan <tiala@...rosoft.com>
> ---
> .../admin-guide/kernel-parameters.txt | 3 +-
> kernel/dma/swiotlb.c | 42 ++++++++++++-------
> 2 files changed, 30 insertions(+), 15 deletions(-)
>
> diff --git a/Documentation/admin-guide/kernel-parameters.txt
> b/Documentation/admin-guide/kernel-parameters.txt
> index 4a6ad177d4b8..ddca09550f76 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -5907,7 +5907,8 @@
> Format: { <int> [,<int>] | force | noforce }
> <int> -- Number of I/O TLB slabs
> <int> -- Second integer after comma. Number of swiotlb
> - areas with their own lock. Must be power of 2.
> + areas with their own lock. Will be rounded up
> + to a power of 2.
> force -- force using of bounce buffers even if they
> wouldn't be automatically used by the kernel
> noforce -- Never use bounce buffers (for debugging)
> diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
> index c39483bf067d..5752db98a1f2 100644
> --- a/kernel/dma/swiotlb.c
> +++ b/kernel/dma/swiotlb.c
> @@ -96,7 +96,13 @@ struct io_tlb_slot {
>
> static void swiotlb_adjust_nareas(unsigned int nareas)
> {
> - if (!is_power_of_2(nareas))
> + /*
> + * Set area number to 1 when input area number
> + * is zero.
> + */
> + if (!nareas)
> + nareas = 1;
> + else if (!is_power_of_2(nareas))
> nareas = roundup_pow_of_two(nareas);
>
> default_nareas = nareas;
> @@ -270,6 +276,7 @@ static void swiotlb_init_io_tlb_mem(struct io_tlb_mem *mem,
> phys_addr_t start,
> for (i = 0; i < mem->nareas; i++) {
> spin_lock_init(&mem->areas[i].lock);
> mem->areas[i].index = 0;
> + mem->areas[i].used = 0;
> }
>
> for (i = 0; i < mem->nslabs; i++) {
> @@ -353,8 +360,8 @@ void __init swiotlb_init_remap(bool addressing_limit, unsigned
> int flags,
> panic("%s: Failed to allocate %zu bytes align=0x%lx\n",
> __func__, alloc_size, PAGE_SIZE);
>
> - mem->areas = memblock_alloc(sizeof(struct io_tlb_area) *
> - default_nareas, SMP_CACHE_BYTES);
> + mem->areas = memblock_alloc(array_size(sizeof(struct io_tlb_area),
> + default_nareas), SMP_CACHE_BYTES);
> if (!mem->areas)
> panic("%s: Failed to allocate mem->areas.\n", __func__);
>
> @@ -479,7 +486,7 @@ void __init swiotlb_exit(void)
> free_pages((unsigned long)mem->slots, get_order(slots_size));
> } else {
> memblock_free_late(__pa(mem->areas),
> - mem->nareas * sizeof(struct io_tlb_area));
> + array_size(sizeof(*mem->areas), mem->nareas));
> memblock_free_late(mem->start, tbl_size);
> memblock_free_late(__pa(mem->slots), slots_size);
> }
> @@ -593,11 +600,12 @@ static unsigned int wrap_area_index(struct io_tlb_mem
> *mem, unsigned int index)
> * Find a suitable number of IO TLB entries size that will fit this request and
> * allocate a buffer from that IO TLB pool.
> */
> -static int swiotlb_do_find_slots(struct io_tlb_mem *mem,
> - struct io_tlb_area *area, int area_index,
> - struct device *dev, phys_addr_t orig_addr,
> +static int swiotlb_do_find_slots(struct device *dev,
> + int area_index, phys_addr_t orig_addr,
> size_t alloc_size, unsigned int alloc_align_mask)
> {
> + struct io_tlb_mem *mem = dev->dma_io_tlb_mem;
> + struct io_tlb_area *area = mem->areas + area_index;
> unsigned long boundary_mask = dma_get_seg_boundary(dev);
> dma_addr_t tbl_dma_addr =
> phys_to_dma_unencrypted(dev, mem->start) & boundary_mask;
> @@ -686,13 +694,12 @@ static int swiotlb_find_slots(struct device *dev, phys_addr_t
> orig_addr,
> size_t alloc_size, unsigned int alloc_align_mask)
> {
> struct io_tlb_mem *mem = dev->dma_io_tlb_mem;
> - int start = raw_smp_processor_id() & ((1U << __fls(mem->nareas)) - 1);
> + int start = raw_smp_processor_id() & (mem->nareas - 1);
> int i = start, index;
>
> do {
> - index = swiotlb_do_find_slots(mem, mem->areas + i, i,
> - dev, orig_addr, alloc_size,
> - alloc_align_mask);
> + index = swiotlb_do_find_slots(dev, i, orig_addr,
> + alloc_size, alloc_align_mask);
> if (index >= 0)
> return index;
> if (++i >= mem->nareas)
> @@ -903,17 +910,24 @@ bool is_swiotlb_active(struct device *dev)
> }
> EXPORT_SYMBOL_GPL(is_swiotlb_active);
>
> +static int io_tlb_used_get(void *data, u64 *val)
> +{
> + *val = mem_used(&io_tlb_default_mem);
> +
> + return 0;
> +}
> +DEFINE_DEBUGFS_ATTRIBUTE(fops_io_tlb_used, io_tlb_used_get, NULL, "%llu\n");
> +
> static void swiotlb_create_debugfs_files(struct io_tlb_mem *mem,
> const char *dirname)
> {
> - unsigned long used = mem_used(mem);
> -
> mem->debugfs = debugfs_create_dir(dirname, io_tlb_default_mem.debugfs);
> if (!mem->nslabs)
> return;
>
> debugfs_create_ulong("io_tlb_nslabs", 0400, mem->debugfs, &mem->nslabs);
> - debugfs_create_ulong("io_tlb_used", 0400, mem->debugfs, &used);
> + debugfs_create_file_unsafe("io_tlb_used", 0400, mem->debugfs, NULL,
> + &fops_io_tlb_used);
> }
>
> static int __init __maybe_unused swiotlb_create_default_debugfs(void)
> --
> 2.25.1
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