linux-kernel - Re: [PATCH 13/17] kvm-arm: Add stage2 page table modifiers

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Message-ID: <5707E541.5040205@arm.com>
Date:	Fri, 8 Apr 2016 18:07:13 +0100
From:	Suzuki K Poulose <Suzuki.Poulose@....com>
To:	Christoffer Dall <christoffer.dall@...aro.org>
Cc:	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	kvmarm@...ts.cs.columbia.edu, kvm@...r.kernel.org,
	marc.zyngier@....com, mark.rutland@....com, will.deacon@....com,
	catalin.marinas@....com
Subject: Re: [PATCH 13/17] kvm-arm: Add stage2 page table modifiers

On 08/04/16 18:03, Christoffer Dall wrote:
> On Fri, Apr 08, 2016 at 04:37:02PM +0100, Suzuki K Poulose wrote:
>> On 08/04/16 14:42, Christoffer Dall wrote:
>>> On Mon, Apr 04, 2016 at 05:26:13PM +0100, Suzuki K Poulose wrote:
>>
>>>>
>>>> -static void clear_pud_entry(struct kvm *kvm, pud_t *pud, phys_addr_t addr)
>>>> +static void clear_stage2_pud_entry(struct kvm *kvm, pud_t *pud, phys_addr_t addr)
>>>>   {
>>>> -	pmd_t *pmd_table = pmd_offset(pud, 0);
>>>> -	VM_BUG_ON(pud_huge(*pud));
>>>> -	pud_clear(pud);
>>>> +	pmd_t *pmd_table __maybe_unused = stage2_pmd_offset(pud, 0);
>>>
>>> The __maybe_unused are slightly ugly, so it may be nicer to create the
>>> stage2_pmd_free() as static inline's if they're defined to do nothing
>>> instead.
>>>
>>
>> Sure, we could do that for stage2. However, we will need to fix the host helpers
>> as well for making such a change in the _hyp version (for 16K + 36bit VA).
>>
>
> I thought the host helpers were already done like that, since we don't
> need the __maybe_unused currently.  If it involves changing core code
> etc. then don't bother.

Unfortunately no, e.g,

include/asm-generic/pgtable-nopud.h defines:

#define pud_free(mm, x)                         do { } while (0)

Cheers
Suzuki