Re: [PATCH] KVM: PPC: Book3S HV: Use RADIX_PTE_INDEX_SIZE in Radix MMU code

[Leonardo Bras <leonardo@linux.ibm.com>]

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Hello Michael,

On Tue, 2020-02-18 at 15:36 +1100, Michael Ellerman wrote:
> In kvmppc_unmap_free_pte() in book3s_64_mmu_radix.c, we use the
> non-constant value PTE_INDEX_SIZE to clear a PTE page.
> 
> We can instead use the constant RADIX_PTE_INDEX_SIZE, because we know
> this code will only be running when the Radix MMU is active.
> 
> Note that we already use RADIX_PTE_INDEX_SIZE for the allocation of
> kvm_pte_cache.
> 
> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
> ---
>  arch/powerpc/kvm/book3s_64_mmu_radix.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/powerpc/kvm/book3s_64_mmu_radix.c b/arch/powerpc/kvm/book3s_64_mmu_radix.c
> index 803940d79b73..134fbc1f029f 100644
> --- a/arch/powerpc/kvm/book3s_64_mmu_radix.c
> +++ b/arch/powerpc/kvm/book3s_64_mmu_radix.c
> @@ -425,7 +425,7 @@ static void kvmppc_unmap_free_pte(struct kvm *kvm, pte_t *pte, bool full,
>  				  unsigned int lpid)
>  {
>  	if (full) {
> -		memset(pte, 0, sizeof(long) << PTE_INDEX_SIZE);
> +		memset(pte, 0, sizeof(long) << RADIX_PTE_INDEX_SIZE);
>  	} else {
>  		pte_t *p = pte;
>  		unsigned long it;

Looks fine to mee. 

For book3s_64, pgtable.h says:
extern unsigned long __pte_index_size;
#define PTE_INDEX_SIZE  __pte_index_size

powerpc/mm/pgtable_64.c defines/export the variable:
unsigned long __pte_index_size;
EXPORT_SYMBOL(__pte_index_size);

And book3s64/radix_pgtable.c set the value in radix__early_init_mmu().
__pte_index_size = RADIX_PTE_INDEX_SIZE;

So I think it's ok to use the value directly in book3s_64_mmu_radix.c.
The include dependency looks fine for that to work.

FWIW:
Reviewed-by: Leonardo Bras <leonardo@linux.ibm.com>


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