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

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Date:	Fri, 8 Apr 2016 19:25:10 +0200
From:	Christoffer Dall <christoffer.dall@...aro.org>
To:	Suzuki K Poulose <Suzuki.Poulose@....com>
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 Fri, Apr 08, 2016 at 06:07:13PM +0100, Suzuki K Poulose wrote:
> 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)
> 

Leave it then :)

Thanks,
-Christoffer