From: "Suzuki K. Poulose" <Suzuki.Poulose@arm.com>
To: Christoffer Dall <christoffer.dall@linaro.org>
Cc: linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, Catalin.Marinas@arm.com,
Will.Deacon@arm.com, Mark.Rutland@arm.com, Marc.Zyngier@arm.com,
kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org,
ard.biesheuvel@linaro.org
Subject: Re: [PATCH 13/15] arm64: kvm: Rewrite fake pgd handling
Date: Tue, 13 Oct 2015 17:04:12 +0100 [thread overview]
Message-ID: <561D2B7C.5050005@arm.com> (raw)
In-Reply-To: <20151013153915.GC21861@cbox>
On 13/10/15 16:39, Christoffer Dall wrote:
> On Mon, Oct 12, 2015 at 10:55:24AM +0100, Suzuki K. Poulose wrote:
>> On 10/10/15 15:52, Christoffer Dall wrote:
>>> Hi Suzuki,
>>
>> Hi Christoffer,
>>
>> Thanks for being patient enough to review the code :-) without much of
>> the comments. I now realise there needs much more documentation than
>> what I have put in already. I am taking care of this in the next
>> revision already.
>>
>>> I had to refresh my mind a fair bit to be able to review this, so I
>>> thought it may be useful to just remind us all what the constraints of
>>> this whole thing is, and make sure we agree on this:
>>>
>>> 1. We fix the IPA max width to 40 bits
>>> 2. We don't support systems with a PARange smaller than 40 bits (do we
>>> check this anywhere or document this anywhere?)
>>
>> AFAIT, no we don't check it anywhere. May be we should. We could plug this
>> into my CPU feature infrastructure[1] and let the is_hype_mode_available()
>> use the info to decide if we can support 40bit IPA ?
>>
>
> If we support 40bit IPA or more, yes, I think that would be sane. Or at
> least put a comment somewhere, perhaps in Documenation.
OK
>>> 3. We always assume we are running on a system with PARange of 40 bits
>>> and we are therefore constrained to use concatination.
>>>
>>> As an implication of (3) above, this code will attempt to allocate 256K
>>> of physically contiguous memory for each VM on the system. That is
>>> probably ok, but I just wanted to point it out in case it raises any
>>> eyebrows for other people following this thread.
>>
>> Right, I will document this in a comment.
>>
>>>> level: 0 1 2 3
>>>> bits : [47] [46 - 36] [35 - 25] [24 - 14] [13 - 0]
>>>> ^ ^ ^
>>>> | | |
>>>> host entry | x---- stage-2 entry
>>>> |
>>>> IPA -----x
>>>
>>> Isn't the stage-2 entry using bits [39:25], because you resolve
>>> more than 11 bits on the initial level of lookup when you concatenate
>>> tables?
>>
>> Yes, the stage-2 entry is just supposed to show the entry level (2).
>>
>
> I don't understand, the stage-2 entry level will be at bit 39, not 35?
>
That picture shows the 'level 2' at which the stage-2 translations begin,
with 16 pages concatenated, which gives 39-25. The host kernel macros,
normally only sees upto bit 35, which is fixed using the kvm_pgd_index()
to pick the right PGD entry for a VA.
Thanks
Suzuki
next prev parent reply other threads:[~2015-10-13 16:04 UTC|newest]
Thread overview: 43+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-09-15 15:41 [PATCHv2 00/15] arm64: 16K translation granule support Suzuki K. Poulose
2015-09-15 15:41 ` [PATCH 01/15] arm64: Move swapper pagetable definitions Suzuki K. Poulose
2015-09-15 15:41 ` [PATCH 02/15] arm64: Handle section maps for swapper/idmap Suzuki K. Poulose
2015-09-15 15:41 ` [PATCH 03/15] arm64: Introduce helpers for page table levels Suzuki K. Poulose
2015-10-07 8:26 ` Christoffer Dall
2015-10-07 9:26 ` Marc Zyngier
2015-10-07 9:48 ` Suzuki K. Poulose
2015-10-08 14:45 ` Christoffer Dall
2015-10-08 17:22 ` Suzuki K. Poulose
2015-10-08 17:28 ` Catalin Marinas
2015-10-09 9:22 ` Suzuki K. Poulose
2015-10-07 9:51 ` Suzuki K. Poulose
2015-09-15 15:41 ` [PATCH 04/15] arm64: Calculate size for idmap_pg_dir at compile time Suzuki K. Poulose
2015-09-15 15:41 ` [PATCH 05/15] arm64: Handle 4 level page table for swapper Suzuki K. Poulose
2015-09-15 15:41 ` [PATCH 06/15] arm64: Clean config usages for page size Suzuki K. Poulose
2015-09-15 15:41 ` [PATCH 07/15] arm64: Kconfig: Fix help text about AArch32 support with 64K pages Suzuki K. Poulose
2015-09-15 15:41 ` [PATCH 08/15] arm64: Check for selected granule support Suzuki K. Poulose
2015-09-15 15:41 ` [PATCH 09/15] arm64: Add page size to the kernel image header Suzuki K. Poulose
2015-10-02 15:49 ` Catalin Marinas
2015-10-02 16:31 ` Catalin Marinas
2015-10-02 16:50 ` Marc Zyngier
2015-10-05 15:43 ` Christoffer Dall
2015-10-05 13:02 ` Suzuki K. Poulose
2015-10-05 13:22 ` Ard Biesheuvel
2015-10-10 17:22 ` Christoffer Dall
2015-09-15 15:41 ` [PATCH 10/15] arm64: kvm: Fix {V}TCR_EL2_TG0 mask Suzuki K. Poulose
2015-10-08 15:17 ` Christoffer Dall
2015-09-15 15:41 ` [PATCH 11/15] arm64: Cleanup VTCR_EL2 computation Suzuki K. Poulose
2015-10-07 10:11 ` Marc Zyngier
2015-10-07 10:23 ` Suzuki K. Poulose
2015-10-10 17:22 ` Christoffer Dall
2015-09-15 15:41 ` [PATCH 12/15] arm: kvm: Move fake PGD handling to arch specific files Suzuki K. Poulose
2015-10-07 10:23 ` Marc Zyngier
2015-10-10 17:22 ` Christoffer Dall
2015-09-15 15:41 ` [PATCH 13/15] arm64: kvm: Rewrite fake pgd handling Suzuki K. Poulose
2015-10-07 11:13 ` Marc Zyngier
2015-10-07 12:21 ` Suzuki K. Poulose
2015-10-10 14:52 ` Christoffer Dall
2015-10-12 9:55 ` Suzuki K. Poulose
2015-10-13 15:39 ` Christoffer Dall
2015-10-13 16:04 ` Suzuki K. Poulose [this message]
2015-09-15 15:41 ` [PATCH 14/15] arm64: Add 16K page size support Suzuki K. Poulose
2015-09-15 15:41 ` [PATCH 15/15] arm64: 36 bit VA Suzuki K. Poulose
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