From: John Garry <john.garry@huawei.com>
To: Jiahui Cen <cenjiahui@huawei.com>, <linux-kernel@vger.kernel.org>
Cc: Wei Xu <xuwei5@hisilicon.com>, Arnd Bergmann <arnd@arndb.de>,
"Bjorn Helgaas" <bhelgaas@google.com>,
Andy Shevchenko <andy.shevchenko@gmail.com>,
<xieyingtai@huawei.com>
Subject: Re: [PATCH] lib/logic_pio: Fix overlap check for pio registery
Date: Mon, 21 Dec 2020 11:12:54 +0000 [thread overview]
Message-ID: <5df9663b-7c6a-6652-2561-9d3889ff94bc@huawei.com> (raw)
In-Reply-To: <006ad6ce-d6b2-59cb-8209-aca3f6e53fec@huawei.com>
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@huawei.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@huawei.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,
John
next prev parent reply other threads:[~2020-12-21 11:14 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-18 6:23 [PATCH] lib/logic_pio: Fix overlap check for pio registery Jiahui Cen
2020-12-18 10:40 ` John Garry
2020-12-21 3:24 ` Jiahui Cen
2020-12-21 11:12 ` John Garry [this message]
2020-12-21 13:04 ` Jiahui Cen
2021-01-15 10:10 ` John Garry
2021-01-18 1:27 ` Jiahui Cen
2021-03-15 10:30 ` John Garry
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