linux-kernel - Re: [PATCH 3/3] vmcore: Convert read_from_oldmem() to take an iov

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Date:   Mon, 13 Dec 2021 09:02:57 +0100
From:   Christoph Hellwig <hch@....de>
To:     "Matthew Wilcox (Oracle)" <willy@...radead.org>
Cc:     Baoquan He <bhe@...hat.com>, Vivek Goyal <vgoyal@...hat.com>,
        Dave Young <dyoung@...hat.com>, kexec@...ts.infradead.org,
        Tiezhu Yang <yangtiezhu@...ngson.cn>,
        linux-kernel@...r.kernel.org,
        Amit Daniel Kachhap <amit.kachhap@....com>,
        Christoph Hellwig <hch@....de>, linux-s390@...r.kernel.org,
        linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH 3/3] vmcore: Convert read_from_oldmem() to take an
 iov_iter

>  
>  ssize_t elfcorehdr_read(char *buf, size_t count, u64 *ppos)
>  {
> -	return read_from_oldmem(buf, count, ppos, 0,
> +	struct kvec kvec = { .iov_base = buf, .iov_len = count };
> +	struct iov_iter iter;
> +
> +	iov_iter_kvec(&iter, READ, &kvec, 1, count);
> +
> +	return read_from_oldmem(&iter, count, ppos,
>  				cc_platform_has(CC_ATTR_GUEST_MEM_ENCRYPT));
>  }

elfcorehdr_read should probably also take an iov_iter while we're at it.

I also don't quite understand why we even need the arch overrides for it,
but that would require some digging into the history of this interface.