linux-kernel - Re: [PATCH 1/1] swiotlb: Fix debugfs reporting of reserved memory pools

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Message-ID: <20230413205244.70dcbdeb@meshulam.tesarici.cz>
Date:   Thu, 13 Apr 2023 20:52:44 +0200
From:   Petr Tesařík <petr@...arici.cz>
To:     Michael Kelley <mikelley@...rosoft.com>
Cc:     hch@....de, m.szyprowski@...sung.com, robin.murphy@....com,
        decui@...rosoft.com, tiala@...rosoft.com,
        petr.tesarik.ext@...wei.com, iommu@...ts.linux.dev,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/1] swiotlb: Fix debugfs reporting of reserved memory
 pools

On Thu, 13 Apr 2023 08:37:30 -0700
Michael Kelley <mikelley@...rosoft.com> wrote:

> For io_tlb_nslabs, the debugfs code reports the correct value for a
> specific reserved memory pool.  But for io_tlb_used, the value reported
> is always for the default pool, not the specific reserved pool. Fix this.
> 
> Fixes: 5c850d31880e ("swiotlb: fix passing local variable to debugfs_create_ulong()")
> Signed-off-by: Michael Kelley <mikelley@...rosoft.com>
> ---
> 
> I don't have a way to test this directly with OF reserved memory, but I
> cobbled together a hack to call rmem_swiotlb_device_init() multiple times
> for different size reserved pools. I verified that reserved pool debugfs entries
> are created as expected and that the value of io_tlb_used is *not* the value
> from the default pool.

Yeah, the only in-tree user is Mediatek Asurada, and I don't have one
either...

The patch looks good to me. But you know, I'm now well-known for
breaking things because of insufficient testing. ;-)

Petr T

>  kernel/dma/swiotlb.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
> index dac42a2..db43de82 100644
> --- a/kernel/dma/swiotlb.c
> +++ b/kernel/dma/swiotlb.c
> @@ -930,7 +930,9 @@ bool is_swiotlb_active(struct device *dev)
>  
>  static int io_tlb_used_get(void *data, u64 *val)
>  {
> -	*val = mem_used(&io_tlb_default_mem);
> +	struct io_tlb_mem *mem = data;
> +
> +	*val = mem_used(mem);
>  	return 0;
>  }
>  DEFINE_DEBUGFS_ATTRIBUTE(fops_io_tlb_used, io_tlb_used_get, NULL,
> "%llu\n"); @@ -943,7 +945,7 @@ static void
> swiotlb_create_debugfs_files(struct io_tlb_mem *mem, return;
>  
>  	debugfs_create_ulong("io_tlb_nslabs", 0400, mem->debugfs,
> &mem->nslabs);
> -	debugfs_create_file("io_tlb_used", 0400, mem->debugfs, NULL,
> +	debugfs_create_file("io_tlb_used", 0400, mem->debugfs, mem,
>  			&fops_io_tlb_used);
>  }
>