linux-kernel - RE: [PATCH] swiotlb: Clean up some coding style and minor issues

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Message-ID: <PH0PR21MB3025314BCD4D8A5ECE8DCE5AD7909@PH0PR21MB3025.namprd21.prod.outlook.com>
Date:   Fri, 22 Jul 2022 05:17:56 +0000
From:   "Michael Kelley (LINUX)" <mikelley@...rosoft.com>
To:     "hch@...radead.org" <hch@...radead.org>
CC:     Tianyu Lan <ltykernel@...il.com>,
        "m.szyprowski@...sung.com" <m.szyprowski@...sung.com>,
        "robin.murphy@....com" <robin.murphy@....com>,
        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: hch@...radead.org <hch@...radead.org> Sent: Thursday, July 21, 2022 10:05 PM
> 
> On Fri, Jul 22, 2022 at 04:03:21AM +0000, Michael Kelley (LINUX) wrote:
> > 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.
> 
> That is already fixed in the dma-mapping tree:
> 
> http://git.infradead.org/users/hch/dma-mapping.git/commitdiff/4a97739474c402e0a14cf6a432f1920262f6811c

Indeed.

> 
> > The other fixes look good to me.
> 
> Can you make that a formal Reviewed-by?

Yes.

Reviewed-by: Michael Kelley <mikelley@...rosoft.com>

> 
> >
> > 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
> >
> ---end quoted text---