linux-kernel - Re: [PATCH] lib/logic_pio: Fix overlap check for pio registery

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Message-ID: <4022fa47-fcff-84dc-ae15-63975fbb2a8e@huawei.com>
Date:   Mon, 15 Mar 2021 10:30:25 +0000
From:   John Garry <john.garry@...wei.com>
To:     Jiahui Cen <cenjiahui@...wei.com>, <linux-kernel@...r.kernel.org>
CC:     Wei Xu <xuwei5@...ilicon.com>, Arnd Bergmann <arnd@...db.de>,
        "Bjorn Helgaas" <bhelgaas@...gle.com>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        <xieyingtai@...wei.com>,
        "linuxarm@...neuler.org" <linuxarm@...neuler.org>,
        Dmitry Vyukov <dvyukov@...gle.com>
Subject: Re: [PATCH] lib/logic_pio: Fix overlap check for pio registery

On 18/01/2021 01:27, Jiahui Cen wrote:

+

Hi Arnd, xu wei,

Any chance we could pick up this patch via arm-soc tree?

The series which I originally included in, below, is stalled a bit.

Thanks,
John

https://lore.kernel.org/lkml/1610729929-188490-1-git-send-email-john.garry@huawei.com/

> Hi John,
> 
> On 2021/1/15 18:10, John Garry wrote:
>> On 21/12/2020 13:04, Jiahui Cen wrote:
>>>> On 21/12/2020 03:24, Jiahui Cen wrote:
>>>>> Hi John,
>>>>>
>>>>> On 2020/12/18 18:40, John Garry wrote:
>>>>>> On 18/12/2020 06:23, Jiahui Cen wrote:
>>>>>>> Since the [start, end) is a half-open interval, a range with the end equal
>>>>>>> to the start of another range should not be considered as overlapped.
>>>>>>>
>>>>>>> Signed-off-by: Jiahui Cen<cenjiahui@...wei.com>
>>>>>>> ---
>>>>>>>      lib/logic_pio.c | 2 +-
>>>>>>>      1 file changed, 1 insertion(+), 1 deletion(-)
>>>>>>>
>>>>>>> diff --git a/lib/logic_pio.c b/lib/logic_pio.c
>>>>>>> index f32fe481b492..445d611f1dc1 100644
>>>>>>> --- a/lib/logic_pio.c
>>>>>>> +++ b/lib/logic_pio.c
>>>>>>> @@ -57,7 +57,7 @@ int logic_pio_register_range(struct logic_pio_hwaddr *new_range)
>>>>>>>                  new_range->flags == LOGIC_PIO_CPU_MMIO) {
>>>>>>>                  /* for MMIO ranges we need to check for overlap */
>>>>>>>                  if (start >= range->hw_start + range->size ||
>>>>>>> -                end < range->hw_start) {
>>>>>>> +                end <= range->hw_start) {
>>>>>> It looks like your change is correct, but should not really have an impact in practice since:
>>>>>> a: BIOSes generally list ascending IO port CPU addresses
>>>>>> b. there is space between IO port CPU address regions
>>>>>>
>>>>>> Have you seen a problem here?
>>>>>>
>>>>> No serious problem. I found it just when I was working on adding support of
>>>>> pci expander bridge for Arm in QEMU. I found the IO window of some extended
>>>>> root bus could not be registered when I inserted the extended buses' _CRS
>>>>> info into DSDT table in the x86 way, which does not sort the buses.
>>>>>
>>>>> Though root buses should be sorted in QEMU, would it be better to accept
>>>>> those non-ascending IO windows?
>>>>>
>>>> ok, so it seems that you have seen a real problem, and this issue is not just detected by code analysis.
>>>>
>>>>> BTW, for b, it seems to be no space between IO windows of different root buses
>>>>> generated by EDK2. Or maybe I missed something obvious.
>>>> I don't know about that. Anyway, your change looks ok.
>>>>
>>>> Reviewed-by: John Garry<john.garry@...wei.com>
>>>>
>>>> BTW, for your virt env, will there be requirement to unregister PCI MMIO ranges? Currently we don't see that in non-virt world.
>>>>
>>> Thanks for your review.
>>>
>>> And currently there is no such a requirement in my virt env.
>>>
>>
>> I am not sure what happened to this patch, but I plan on sending some patches in this area soon - do you want me to include this one?
>>
> 
> Sorry for replying late. It's appreciated if you can include this patch.
> 
> Thanks!
> Jiahui
> 
>> Thanks,
>> John
>>
>> .
> .
>