linux-kernel - Re: [PATCH v3 10/20] kvm: arm64: Dynamic configuration of VTTBR mask

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Message-ID: <1696a35f-9cd5-d807-f2e9-41d9f19d919a@arm.com>
Date:   Wed, 4 Jul 2018 09:29:06 +0100
From:   Suzuki K Poulose <suzuki.poulose@....com>
To:     Auger Eric <eric.auger@...hat.com>,
        linux-arm-kernel@...ts.infradead.org
Cc:     cdall@...nel.org, kvm@...r.kernel.org, marc.zyngier@....com,
        catalin.marinas@....com, punit.agrawal@....com,
        will.deacon@....com, linux-kernel@...r.kernel.org,
        qemu-devel@...gnu.org, julien.grall@....com, james.morse@....com,
        kvmarm@...ts.cs.columbia.edu
Subject: Re: [PATCH v3 10/20] kvm: arm64: Dynamic configuration of VTTBR mask

On 07/04/2018 09:24 AM, Auger Eric wrote:
>>>> + *
>>>> + * We have a magic formula for the Magic_N below.
>>>> + *
>>>> + *  Magic_N(PAGE_SIZE, Entry_Level) = 64 - ((PAGE_SHIFT - 3) *
>>>> Number of levels)
>>
>> [0] ^^^
>>
>>
>>
>>>> + *
>>>> + * where number of levels = (4 - Entry_Level).
>>
>> ^^^ Doesn't this help make it clear ? Using the expansion makes it a bit
>> more
>> unreadable below.
> 
> I just wanted to mention the tables you refer (D4-23 and D4-25) give
> Magic_N for a larger scope as they deal with any lookup level while we
> only care about the entry level for BADDR. So I was a little bit
> confused when reading the explanation but that's not a big deal.

Ah, ok. I will try to clarify it.

Cheers
Suzuki