From: John Garry <john.garry@huawei•com>
To: Will Deacon <will@kernel•org>
Cc: Catalin Marinas <catalin.marinas@arm•com>,
Mark Brown <broonie@kernel•org>,
linux-arm-kernel@lists•infradead.org
Subject: Re: [PATCH v4 0/4] E0PD support
Date: Thu, 31 Oct 2019 14:13:52 +0000 [thread overview]
Message-ID: <a074ae3a-273f-5be2-7e4d-267e6103a094@huawei.com> (raw)
In-Reply-To: <20191031124217.GE26059@willie-the-truck>
On 31/10/2019 12:42, Will Deacon wrote:
> On Thu, Oct 31, 2019 at 12:13:35PM +0000, John Garry wrote:
>> On 31/10/2019 11:26, Will Deacon wrote:
>>> On Thu, Oct 24, 2019 at 10:42:03PM +0100, Mark Brown wrote:
>>>> This series adds support for E0PD. We enable E0PD unconditionally where
>>>> present on systems where all the CPUs in the system support E0PD and
>>>> change to not enabling KPTI by default on systems where we have enabled
>>>> E0PD. It also converts the runtime checks for use of non-global mappings
>>>> into a variable.
>>>
>>> Although I welcome the simplification introduced by this patch set, I'm
>>> worried that we might be removing a significant optimisation to KASLR
>>> boot-time on machines with large memory. John reported issues with this
>>> in the past, so I'm looping him in in case he has a chance to test this
>>> (branch here [1]). Of course, I could just be missing something since
>>> this code was really subtle to begin with.
>>
>> I booted our D05 and D06 boards with that branch and did not experience the
>> pauses which we reported some time ago.
>
> Hmm. So I annotated the code locally and I see that we do rewrite swapper
> in this case, so I'm surprised you're not seeing the performance issue
> you ran into with this before. Have you got KASLR enabled and are you
> passing a non-zero seed?
Just to confirm: yes and no (both boards pump out "EFI_RNG_PROTOCOL
unavailable, no randomness supplied")
Thanks,
John
>
> Will
> .
>
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next prev parent reply other threads:[~2019-10-31 14:14 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-24 21:42 [PATCH v4 0/4] E0PD support Mark Brown
2019-10-24 21:42 ` [PATCH v4 1/4] arm64: Add initial support for E0PD Mark Brown
2019-10-24 21:42 ` [PATCH v4 2/4] arm64: Factor out checks for KASLR in KPTI code into separate function Mark Brown
2019-10-24 21:42 ` [PATCH v4 3/4] arm64: Don't use KPTI where we have E0PD Mark Brown
2019-10-24 21:42 ` [PATCH v4 4/4] arm64: Use a variable to store non-global mappings decision Mark Brown
2019-10-30 12:13 ` Catalin Marinas
2019-10-30 12:41 ` Mark Brown
2019-10-30 14:17 ` Catalin Marinas
2019-10-31 8:18 ` Mark Brown
2019-10-31 10:18 ` Catalin Marinas
2019-10-31 10:35 ` Mark Brown
2019-11-04 17:20 ` Mark Brown
2019-10-30 12:26 ` [PATCH v4 0/4] E0PD support Catalin Marinas
2019-10-30 12:54 ` Mark Brown
2019-10-31 11:26 ` Will Deacon
2019-10-31 12:13 ` John Garry
2019-10-31 12:42 ` Will Deacon
2019-10-31 13:00 ` Mark Brown
2019-10-31 13:09 ` Will Deacon
2019-10-31 14:13 ` John Garry [this message]
2019-10-31 16:06 ` Ard Biesheuvel
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