linux-kernel - Re: [PATCH 1/1] ARM: LPAE: use phys_addr_t instead of unsigned long in outercache hooks

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Date:   Tue, 29 Dec 2020 14:30:56 +0800
From:   "Leizhen (ThunderTown)" <thunder.leizhen@...wei.com>
To:     Russell King - ARM Linux admin <linux@...linux.org.uk>
CC:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Will Deacon <will.deacon@....com>,
        Jason Cooper <jason@...edaemon.net>,
        Haojian Zhuang <haojian.zhuang@...il.com>,
        Arnd Bergmann <arnd@...db.de>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/1] ARM: LPAE: use phys_addr_t instead of unsigned long
 in outercache hooks



On 2020/12/26 20:13, Russell King - ARM Linux admin wrote:
> On Fri, Dec 25, 2020 at 07:44:58PM +0800, Zhen Lei wrote:
>> The outercache of some Hisilicon SOCs support physical addresses wider
>> than 32-bits. The unsigned long datatype is not sufficient for mapping
>> physical addresses >= 4GB. The commit ad6b9c9d78b9 ("ARM: 6671/1: LPAE:
>> use phys_addr_t instead of unsigned long in outercache functions") has
>> already modified the outercache functions. But the parameters of the
>> outercache hooks are not changed. This patch use phys_addr_t instead of
>> unsigned long in outercache hooks: inv_range, clean_range, flush_range.
>>
>> To ensure the outercache that does not support LPAE works properly, do
>> cast phys_addr_t to unsigned long by adding a middle-tier function.
> 
> Please don't do that. The cast can be done inside the L2 functions
> themselves without needing all these additional functions.

OK. At first, I wanted to fit in like this:

-static void l2c220_inv_range(unsigned long start, unsigned long end)
+static void l2c220_inv_range(phys_addr_t lpae_start, phys_addr_t lpae_end)
 {
+  unsigned long start = lpae_start;
+  unsigned long end = lpae_end;


> 
> We probably ought to also add some protection against addresses > 4GB,
> although these are hot paths, so we don't want to add tests in these
> functions. Maybe instead checking whether the system has memory above
> 4GB while the L2 cache is being initialised would be a good idea?
> 

I'm sorry, I didn't quite understand what you meant. Currently, the
biggest problem is the compilation problem. The sizeof(long) may be
32, and the 64-bit physical address cannot be transferred from outcache
functions to outcache hooks.