From: Thomas Gleixner <tglx@linutronix.de>
To: Yaohui Wang <yaohuiwang@linux.alibaba.com>, dave.hansen@linux.intel.com
Cc: luto@kernel.org, peterz@infradead.org, mingo@redhat.com,
bp@alien8.de, x86@kernel.org, linux-kernel@vger.kernel.org,
Ben Luo <luoben@linux.alibaba.com>,
Yahui Wang <yaohuiwang@linux.alibaba.com>
Subject: Re: [PATCH v2 1/2] mm: fix the pfn calculation mistake in __ioremap_check_ram
Date: Sat, 19 Jun 2021 23:22:08 +0200 [thread overview]
Message-ID: <87r1gxh7nj.ffs@nanos.tec.linutronix.de> (raw)
In-Reply-To: <20210611042147.80744-2-yaohuiwang@linux.alibaba.com>
Yaohui!
On Fri, Jun 11 2021 at 12:21, Yaohui Wang wrote:
A few formal things upfront. The prefix of the subject is incorrect. It
should be "x86/ioremap:" git log $FILE helps to figure that out.
Looking at the Signed-off-by chain below this misses either a
From: Ben Luo <luoben@linux.alibaba.com>
right at the top of the changelog or a Co-Developed-by tag. See
Documentation/process/
> In arch/x86/mm/ioremap.c:__ioremap_check_ram, the original pfn
> wrapping
Just "In __ioremap_check_ram() ..." please. The file name is
uninteresting and we want the '()' at the end of the symbol so it's
obvious that this is a function.
> calculation may cause the pfn range to ignore the very start page, if
> res->start is not page-aligned, or the very end page, if res->end is not
> page aligned.
>
> So start_pfn should wrap down the res->start address, and end_pfn should
> wrap up the res->end address. This makes the pfn range completely
> contain [res->start, res->end] ram range. This check is more strict and is
> more reasonable.
This lacks a "Fixes:" tag
> Signed-off-by: Ben Luo <luoben@linux.alibaba.com>
> Signed-off-by: Yahui Wang <yaohuiwang@linux.alibaba.com>
> ---
> arch/x86/mm/ioremap.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/mm/ioremap.c b/arch/x86/mm/ioremap.c
> index 9e5ccc56f..79adf0d2d 100644
> --- a/arch/x86/mm/ioremap.c
> +++ b/arch/x86/mm/ioremap.c
> @@ -74,8 +74,8 @@ static unsigned int __ioremap_check_ram(struct resource *res)
> if ((res->flags & IORESOURCE_SYSTEM_RAM) != IORESOURCE_SYSTEM_RAM)
> return 0;
>
> - start_pfn = (res->start + PAGE_SIZE - 1) >> PAGE_SHIFT;
> - stop_pfn = (res->end + 1) >> PAGE_SHIFT;
> + start_pfn = res->start >> PAGE_SHIFT;
> + stop_pfn = (res->end + PAGE_SIZE) >> PAGE_SHIFT;
Please make that:
start_pfn = PFN_DOWN(res->start);
stop_pfn = PFN_UP(res->end);
which gives you the first and the last PFN of that range. That obviously
requires to fix the below as well, but that code is unreadable anyway.
> if (stop_pfn > start_pfn) {
> for (i = 0; i < (stop_pfn - start_pfn); ++i)
> if (pfn_valid(start_pfn + i) &&
npages = stop_pfn - start_pfn + 1;
for (i = 0; i < npages; i++) {
if (.....)
}
you get the idea, right?
Thanks,
tglx
next prev parent reply other threads:[~2021-06-19 21:24 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-11 4:21 [PATCH v2 0/2] mm: unexpected behavior of __ioremap_caller Yaohui Wang
2021-06-11 4:21 ` [PATCH v2 1/2] mm: fix the pfn calculation mistake in __ioremap_check_ram Yaohui Wang
2021-06-19 21:22 ` Thomas Gleixner [this message]
2021-06-21 8:06 ` Thomas Gleixner
2021-06-11 4:21 ` [PATCH v2 2/2] mm: fix boundary judgment issues in kernel/resource.c Yaohui Wang
2021-06-19 22:16 ` Thomas Gleixner
2021-06-21 6:12 ` Yaohui Wang
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