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Date:   Sat, 8 Oct 2022 05:26:49 +0000
From:   Stafford Horne <shorne@gmail.com>
To:     linux-kernel@vger.kernel.org
Cc:     openrisc@lists.librecores.org, Jann Horn <jannh@google.com>,
        Jonas Bonn <jonas@southpole.se>,
        Stefan Kristiansson <stefan.kristiansson@saunalahti.fi>,
        Steven Price <steven.price@arm.com>
Subject: Re: [PATCH] openrisc: Fix pagewalk usage in arch_dma_{clear,
 set}_uncached
Message-ID: <Y0EKGV38rvbbXZF6@oscomms1>
References: <20221008052422.29695-1-shorne@gmail.com>
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Sorry, meant to tag this as v2. But I missed the command line option as I am on
a new system and was working on getting aliases and other things setup to send
this mail.

-Stafford

On Sat, Oct 08, 2022 at 06:24:21AM +0100, Stafford Horne wrote:
> From: Jann Horn <jannh@google.com>
> 
> Since commit 8782fb61cc848 ("mm: pagewalk: Fix race between unmap and page
> walker"), walk_page_range() on kernel ranges won't work anymore,
> walk_page_range_novma() must be used instead.
> 
> Note: I don't have an openrisc development setup, so this is completely
> untested.
> 
> Fixes: 8782fb61cc848 ("mm: pagewalk: Fix race between unmap and page walker")
> Signed-off-by: Jann Horn <jannh@google.com>
> Signed-off-by: Stafford Horne <shorne@gmail.com>
> ---
> Since v1:
>  - Repost to include LKML.
>  - Added my SOB
>  - I tested this by booking this on the qemu virt platform and it works fine.
> 
>  arch/openrisc/kernel/dma.c | 16 ++++++++--------
>  1 file changed, 8 insertions(+), 8 deletions(-)
> 
> diff --git a/arch/openrisc/kernel/dma.c b/arch/openrisc/kernel/dma.c
> index a82b2caaa560..b3edbb33b621 100644
> --- a/arch/openrisc/kernel/dma.c
> +++ b/arch/openrisc/kernel/dma.c
> @@ -74,10 +74,10 @@ void *arch_dma_set_uncached(void *cpu_addr, size_t size)
>  	 * We need to iterate through the pages, clearing the dcache for
>  	 * them and setting the cache-inhibit bit.
>  	 */
> -	mmap_read_lock(&init_mm);
> -	error = walk_page_range(&init_mm, va, va + size, &set_nocache_walk_ops,
> -			NULL);
> -	mmap_read_unlock(&init_mm);
> +	mmap_write_lock(&init_mm);
> +	error = walk_page_range_novma(&init_mm, va, va + size,
> +			&set_nocache_walk_ops, NULL, NULL);
> +	mmap_write_unlock(&init_mm);
>  
>  	if (error)
>  		return ERR_PTR(error);
> @@ -88,11 +88,11 @@ void arch_dma_clear_uncached(void *cpu_addr, size_t size)
>  {
>  	unsigned long va = (unsigned long)cpu_addr;
>  
> -	mmap_read_lock(&init_mm);
> +	mmap_write_lock(&init_mm);
>  	/* walk_page_range shouldn't be able to fail here */
> -	WARN_ON(walk_page_range(&init_mm, va, va + size,
> -			&clear_nocache_walk_ops, NULL));
> -	mmap_read_unlock(&init_mm);
> +	WARN_ON(walk_page_range_novma(&init_mm, va, va + size,
> +			&clear_nocache_walk_ops, NULL, NULL));
> +	mmap_write_unlock(&init_mm);
>  }
>  
>  void arch_sync_dma_for_device(phys_addr_t addr, size_t size,
> -- 
> 2.37.2
>