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, kvmarm@lists.cs.columbia.edu,
kvm@vger.kernel.org, marc.zyngier@arm.com, mark.rutland@arm.com,
will.deacon@arm.com, catalin.marinas@arm.com
Subject: Re: [PATCH 15/17] kvm: arm64: Get rid of fake page table levels
Date: Tue, 12 Apr 2016 14:03:25 +0100 [thread overview]
Message-ID: <570CF21D.8000600@arm.com> (raw)
In-Reply-To: <20160412121414.GA3039@cbox>
On 12/04/16 13:14, Christoffer Dall wrote:
> On Mon, Apr 11, 2016 at 03:33:45PM +0100, Suzuki K Poulose wrote:
>> On 08/04/16 16:05, Christoffer Dall wrote:
>>> On Mon, Apr 04, 2016 at 05:26:15PM +0100, Suzuki K Poulose wrote:
>>
>>>> -#if PGDIR_SHIFT > KVM_PHYS_SHIFT
>>>> -#define PTRS_PER_S2_PGD_SHIFT 0
>>>> -#else
>>>> -#define PTRS_PER_S2_PGD_SHIFT (KVM_PHYS_SHIFT - PGDIR_SHIFT)
>>>> -#endif
>>>> -#define PTRS_PER_S2_PGD (1 << PTRS_PER_S2_PGD_SHIFT)
>>>> +#define STAGE2_PGTABLE_LEVELS ARM64_HW_PGTABLE_LEVELS(KVM_PHYS_SHIFT - 4)
>>>>
>>>> /*
>>>> - * If we are concatenating first level stage-2 page tables, we would have less
>>>> - * than or equal to 16 pointers in the fake PGD, because that's what the
>>>> - * architecture allows. In this case, (4 - CONFIG_PGTABLE_LEVELS)
>>>> - * represents the first level for the host, and we add 1 to go to the next
>>>> - * level (which uses contatenation) for the stage-2 tables.
>
> just noticed: s/contatenation/concatenation/
Thanks for catching that. Will fix it.
>>> which case this should be reworded to just state the assumptions and why
>>> this is a good assumption.
>>>
>>> (If my assumptions are wrong here, then there are also weird cases where
>>> the host does huge pages at the PMD level and we don't. Not sure I can
>>> see the full ramifications of that.)
>>
>> I am sorry, I didn't get your point about the PMD level.
>>
>
> Right, I expressed that terribly, and I may have gotten myself confused
> when writing that.
>
> My concern is this: if the number of levels between the host and stage-2
> are different, and the host uses huge pmd mappings (either THP or huge
> tlb fs), then do we always do the right thing for stage-2 tables, even
> if we support the case with more levels in Stage-2 than on the host?
Yes. We are safe with PMD (level 2). In the worst case we will have a 2level
page table at host and say 4 at stage2. In either case, we have a PMD level
(which in host is folded to PGD) and both will use section mapping at level 2
for huge pmd. Also pmd_huge() doesn't care if the PMD is folded or not. So,
we are fine with that. I hope that answers your question.
>
> Thanks for trying to parse my crytptic and potentially nonsensical
> questions.
No no, they make absolute sense. I had gone through these questions myself initially
when I wrote the series, so its good to share them :-).
Btw, I have rebased my series to kvmarm and have addressed the comments. I will post
them after a round of testing.
Cheers
Suzuki
next prev parent reply other threads:[~2016-04-12 13:03 UTC|newest]
Thread overview: 52+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-04-04 16:26 [PATCH 00/17] kvm-arm: Add stage2 page table walker Suzuki K Poulose
2016-04-04 16:26 ` [PATCH 01/17] arm64: Reuse TCR field definitions for EL1 and EL2 Suzuki K Poulose
2016-04-08 12:43 ` Christoffer Dall
2016-04-04 16:26 ` [PATCH 02/17] arm64: Cleanup VTCR_EL2 and VTTBR field values Suzuki K Poulose
2016-04-08 12:43 ` Christoffer Dall
2016-04-08 12:45 ` Suzuki K Poulose
2016-04-04 16:26 ` [PATCH 03/17] kvm arm: Move fake PGD handling to arch specific files Suzuki K Poulose
2016-04-04 16:26 ` [PATCH 04/17] arm64: Introduce pmd_thp_or_huge Suzuki K Poulose
2016-04-08 12:43 ` Christoffer Dall
2016-04-04 16:26 ` [PATCH 05/17] kvm-arm: Replace kvm_pmd_huge with pmd_thp_or_huge Suzuki K Poulose
2016-04-08 12:43 ` Christoffer Dall
2016-04-04 16:26 ` [PATCH 06/17] kvm-arm: Remove kvm_pud_huge() Suzuki K Poulose
2016-04-08 12:44 ` Christoffer Dall
2016-04-04 16:26 ` [PATCH 07/17] kvm-arm: arm32: Introduce stage2 page table helpers Suzuki K Poulose
2016-04-08 12:43 ` Christoffer Dall
2016-04-08 14:39 ` Suzuki K Poulose
2016-04-04 16:26 ` [PATCH 08/17] kvm-arm: arm: Introduce hyp page table empty checks Suzuki K Poulose
2016-04-08 13:15 ` Christoffer Dall
2016-04-04 16:26 ` [PATCH 09/17] kvm-arm: arm64: Introduce stage2 page table helpers Suzuki K Poulose
2016-04-08 13:15 ` Christoffer Dall
2016-04-04 16:26 ` [PATCH 10/17] kvm-arm: arm64: Introduce hyp page table empty checks Suzuki K Poulose
2016-04-08 13:15 ` Christoffer Dall
2016-04-04 16:26 ` [PATCH 11/17] kvm-arm: Use explicit stage2 helper routines Suzuki K Poulose
2016-04-08 13:16 ` Christoffer Dall
2016-04-04 16:26 ` [PATCH 12/17] kvm-arm: Add explicit hyp page table modifiers Suzuki K Poulose
2016-04-08 13:15 ` Christoffer Dall
2016-04-08 15:09 ` Marc Zyngier
2016-04-08 15:16 ` Christoffer Dall
2016-04-08 15:22 ` Marc Zyngier
2016-04-08 15:22 ` Suzuki K Poulose
2016-04-08 15:25 ` Christoffer Dall
2016-04-04 16:26 ` [PATCH 13/17] kvm-arm: Add stage2 " Suzuki K Poulose
2016-04-08 13:42 ` Christoffer Dall
2016-04-08 15:37 ` Suzuki K Poulose
2016-04-08 17:03 ` Christoffer Dall
2016-04-08 17:07 ` Suzuki K Poulose
2016-04-08 17:25 ` Christoffer Dall
2016-04-04 16:26 ` [PATCH 14/17] kvm-arm: Cleanup kvm_* wrappers Suzuki K Poulose
2016-04-08 15:05 ` Christoffer Dall
2016-04-04 16:26 ` [PATCH 15/17] kvm: arm64: Get rid of fake page table levels Suzuki K Poulose
2016-04-08 15:05 ` Christoffer Dall
2016-04-11 14:33 ` Suzuki K Poulose
2016-04-12 12:14 ` Christoffer Dall
2016-04-12 13:03 ` Suzuki K Poulose [this message]
2016-04-12 13:11 ` Christoffer Dall
2016-04-13 17:49 ` Suzuki K Poulose
2016-04-14 12:18 ` Christoffer Dall
2016-04-04 16:26 ` [PATCH 16/17] kvm-arm: Cleanup stage2 pgd handling Suzuki K Poulose
2016-04-08 15:08 ` Christoffer Dall
2016-04-04 16:26 ` [PATCH 17/17] arm64: kvm: Add support for 16K pages Suzuki K Poulose
2016-04-08 15:13 ` Christoffer Dall
2016-04-08 15:15 ` [PATCH 00/17] kvm-arm: Add stage2 page table walker Christoffer Dall
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