From: Babu Moger <babu.moger@amd.com>
To: Dave Hansen <dave.hansen@intel.com>,
corbet@lwn.net, tglx@linutronix.de, mingo@redhat.com,
bp@alien8.de, hpa@zytor.com, pbonzini@redhat.com,
sean.j.christopherson@intel.com
Cc: x86@kernel.org, vkuznets@redhat.com, wanpengli@tencent.com,
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dave.hansen@linux.intel.com, luto@kernel.org,
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kvm@vger.kernel.org
Subject: Re: [PATCH v4 1/3] arch/x86: Update config and kernel doc for MPK feature on AMD
Date: Wed, 13 May 2020 10:56:42 -0500 [thread overview]
Message-ID: <e96a653d-bd13-ed25-81e2-b7301d7f92f1@amd.com> (raw)
In-Reply-To: <e8dbb26f-9358-cef7-aae2-14d8b5700245@intel.com>
On 5/13/20 10:09 AM, Dave Hansen wrote:
> On 5/12/20 4:58 PM, Babu Moger wrote:
>> +config X86_MEMORY_PROTECTION_KEYS
>> + # Both Intel and AMD platforms support "Memory Protection Keys"
>> + # feature. So add a generic option X86_MEMORY_PROTECTION_KEYS
>> + # and set the option whenever X86_INTEL_MEMORY_PROTECTION_KEYS
>> + # is set. This is to avoid the confusion about the feature
>> + # availability on AMD platforms. Also renaming the old option
>> + # would cause the user an extra prompt during the kernel
>> + # configuration. So avoided changing the old config name.
>> + def_bool X86_INTEL_MEMORY_PROTECTION_KEYS
>
> Hi Babu,
>
> I made a request earlier for an end date (or version) to be included
> here. I believe that appeared in one of your earlier versions, but it
> was removed in later ones.
>
> Was there a reason for that?
Dave, Sorry, I misunderstood that. I thought we probably are not going to
change the sources/makefile(ifdefs mostly) as it was technically not
required. Now I am reading that we are going to change that in the future
and just keep X86_MEMORY_PROTECTION_KEYS going forward.
Sure. I will add the text you proposed. Please feel free to correct again.
>
> I'd really prefer to put some kind of expiration date on the config
> option. It will outlive us all otherwise.
>
>> Memory Protection Keys for Userspace (PKU aka PKEYs) is a feature
>> which is found on Intel's Skylake "Scalable Processor" Server CPUs.
>> -It will be avalable in future non-server parts.
>> +It will be available in future non-server parts. Also, AMD64
>> +Architecture Programmer’s Manual defines PKU feature in AMD processors.
>
> I actually worked pretty hard to make that sentence useful to Linux
> users. Instead of forcing them to imply that it will be available on
> future AMD CPUs, can we just come out and say it? Can we give any more
> information to our users?
>
> Naming the AMD manual in which the feature is defined doesn't really
> help our users. Let's not waste the bytes on it.
>
> How about:
>
> Memory Protection Keys for Userspace (PKU aka PKEYs) is a
> feature which is found on Intel's Skylake (and later) "Scalable
> Processor" Server CPUs. It will be avalable in future non-
> server Intel parts and future AMD parts.
This should be good enough. Thanks.
>
> Any clarity you can add, such as to say what AMD is doing for server vs.
> client would be nice.
>
> BTW, when I first submitted pkeys, I didn't have any statement like this
> in the changelog or documentation. Ingo, I think, asked for it and I
> worked with folks inside Intel to figure out how much we could say
> publicly about our plans. A similar effort from AMD would be much
> appreciated here.
>
next prev parent reply other threads:[~2020-05-13 15:56 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-12 23:58 [PATCH v4 0/3] arch/x86: Enable MPK feature on AMD Babu Moger
2020-05-12 23:58 ` [PATCH v4 1/3] arch/x86: Update config and kernel doc for " Babu Moger
2020-05-13 15:09 ` Dave Hansen
2020-05-13 15:56 ` Babu Moger [this message]
2020-05-12 23:59 ` [PATCH v4 2/3] KVM: x86: Move pkru save/restore to x86.c Babu Moger
2020-05-12 23:59 ` [PATCH v4 3/3] KVM: x86: Move MPK feature detection to common code Babu Moger
2020-05-13 15:35 ` [PATCH v4 0/3] arch/x86: Enable MPK feature on AMD Paolo Bonzini
2020-05-13 16:00 ` Babu Moger
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