Date:   Sun, 2 Jan 2022 23:54:46 -0800
From:   Christoph Hellwig <hch@infradead.org>
To:     Tianyu Lan <ltykernel@gmail.com>
Cc:     hch@infradead.org, m.szyprowski@samsung.com, robin.murphy@arm.com,
        michael.h.kelley@microsoft.com, kys@microsoft.com,
        Tianyu Lan <Tianyu.Lan@microsoft.com>,
        iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org,
        vkuznets@redhat.com, brijesh.singh@amd.com, konrad.wilk@oracle.com,
        hch@lst.de, wei.liu@kernel.org, parri.andrea@gmail.com,
        thomas.lendacky@amd.com, kernel test robot <lkp@intel.com>
Subject: Re: [PATCH] Swiotlb: Add CONFIG_HAS_IOMEM check around memremap() in
 the swiotlb_mem_remap()
Message-ID: <YdKrxgnpT0Dc0t2T@infradead.org>
References: <20211231165640.1245751-1-ltykernel@gmail.com>
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On Fri, Dec 31, 2021 at 11:56:40AM -0500, Tianyu Lan wrote:
> From: Tianyu Lan <Tianyu.Lan@microsoft.com>
> 
> HAS_IOMEM option may not be selected on some platforms(e.g, s390) and this
> will cause compile error due to miss memremap() implementation. Fix it via
> adding HAS_IOMEM check around memremap() in the swiotlb.c.
> 
> Reported-by: kernel test robot <lkp@intel.com>
> Signed-off-by: Tianyu Lan <Tianyu.Lan@microsoft.com>
> ---
>  kernel/dma/swiotlb.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
> index b36c1cdd0c4f..3de651ba38cc 100644
> --- a/kernel/dma/swiotlb.c
> +++ b/kernel/dma/swiotlb.c
> @@ -167,6 +167,7 @@ static void *swiotlb_mem_remap(struct io_tlb_mem *mem, unsigned long bytes)
>  {
>  	void *vaddr = NULL;
>  
> +#ifdef CONFIG_HAS_IOMEM

Please stub out all of swiotlb_mem_remap instead of the ifdef inside the
function.