linux-kernel - Re: [RFC PATCH] arm64: fix the missing ktpi= cmdline check in arm64_kernel_unmapped_at

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Date:   Thu, 19 Mar 2020 14:14:55 +0800
From:   Hongbo Yao <yaohongbo@...wei.com>
To:     Will Deacon <will@...nel.org>, Mark Brown <broonie@...nel.org>
CC:     Mark Rutland <mark.rutland@....com>,
        <linux-kernel@...r.kernel.org>, <catalin.marinas@....com>,
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [RFC PATCH] arm64: fix the missing ktpi= cmdline check in
 arm64_kernel_unmapped_at_el0()



On 2020/3/19 4:13, Will Deacon wrote:
> On Wed, Mar 18, 2020 at 11:32:17AM +0000, Mark Brown wrote:
>> On Tue, Mar 17, 2020 at 09:01:54PM +0000, Will Deacon wrote:
>>> On Tue, Mar 17, 2020 at 04:36:38PM +0000, Mark Brown wrote:
>>
>>>> I'd need to go back and retest to confirm but it looks like always had
>>>> the issue that we'd install some nG mappings early even with KPTI
>>>> disabled on the command line so your change is just restoring the
>>>> previous behaviour and we're no worse than we were before.
>>
>>> Urgh, this code brings back really bad memories :( :( :(
>>
>> Tell me about it.
>>
>>> So I've hacked the following, which appears to work but damn I'd like
>>> somebody else to look at this. I also have a nagging feeling that you
>>> implemented it like this at some point, but we tried to consolidate things
>>> during review.
>>
>>> Thoughts?
>>
>> I don't think I did *exactly* this but it's familiar yeah.  It looks
>> sensible and I can't think of any problems but that doesn't mean there
>> aren't any.
> 
> Well, thanks for having a look!
> 
> Hongbo -- please can you confirm that this fixes the problem that you are
> seeing?
Hi, Will,
Sorry for the late response.

This fixes the problem for me.
Tested-by: Hongbo Yao <yaohongbo@...wei.com>

Thanks,
Hongbo.

> Will
> 
> .
>