Subject: Re: [PATCH] KVM: PPC: BOOK3S: HV: Use base page size when comparing against slb value

From: Alexander Graf <[email-masked]>
Date: Fri, 13 Jun 2014 12:03:14 +0200

On 13.06.14 09:23, Aneesh Kumar K.V wrote:
> With guest supporting Multiple page size per segment (MPSS),
> hpte_page_size returns actual page size used. Add a new function to
> return base page size and use that to compare against the the page size
> calculated from SLB

Why? What does this fix? Is this a bug fix, an enhancement? Don't 
describe only what you do, but also why you do it.

Alex

>
> Signed-off-by: Aneesh Kumar K.V <[email-masked]>
> ---
>   arch/powerpc/include/asm/kvm_book3s_64.h | 19 +++++++++++++++++--
>   arch/powerpc/kvm/book3s_64_mmu_hv.c      |  2 +-
>   arch/powerpc/kvm/book3s_hv_rm_mmu.c      |  2 +-
>   3 files changed, 19 insertions(+), 4 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/kvm_book3s_64.h b/arch/powerpc/include/asm/kvm_book3s_64.h
> index 34422be566ce..3d0f3fb9c6b6 100644
> --- a/arch/powerpc/include/asm/kvm_book3s_64.h
> +++ b/arch/powerpc/include/asm/kvm_book3s_64.h
> @@ -202,8 +202,10 @@ static inline unsigned long compute_tlbie_rb(unsigned long v, unsigned long r,
>   	return rb;
>   }
>   
> -static inline unsigned long hpte_page_size(unsigned long h, unsigned long l)
> +static inline unsigned long __hpte_page_size(unsigned long h, unsigned long l,
> +					     bool is_base_size)
>   {
> +
>   	int size, a_psize;
>   	/* Look at the 8 bit LP value */
>   	unsigned int lp = (l >> LP_SHIFT) & ((1 << LP_BITS) - 1);
> @@ -218,14 +220,27 @@ static inline unsigned long hpte_page_size(unsigned long h, unsigned long l)
>   				continue;
>   
>   			a_psize = __hpte_actual_psize(lp, size);
> -			if (a_psize != -1)
> +			if (a_psize != -1) {
> +				if (is_base_size)
> +					return 1ul << mmu_psize_defs[size].shift;
>   				return 1ul << mmu_psize_defs[a_psize].shift;
> +			}
>   		}
>   
>   	}
>   	return 0;
>   }
>   
> +static inline unsigned long hpte_page_size(unsigned long h, unsigned long l)
> +{
> +	return __hpte_page_size(h, l, 0);
> +}
> +
> +static inline unsigned long hpte_base_page_size(unsigned long h, unsigned long l)
> +{
> +	return __hpte_page_size(h, l, 1);
> +}
> +
>   static inline unsigned long hpte_rpn(unsigned long ptel, unsigned long psize)
>   {
>   	return ((ptel & HPTE_R_RPN) & ~(psize - 1)) >> PAGE_SHIFT;
> diff --git a/arch/powerpc/kvm/book3s_64_mmu_hv.c b/arch/powerpc/kvm/book3s_64_mmu_hv.c
> index f53cf2eae36a..7ff45ed27c65 100644
> --- a/arch/powerpc/kvm/book3s_64_mmu_hv.c
> +++ b/arch/powerpc/kvm/book3s_64_mmu_hv.c
> @@ -1567,7 +1567,7 @@ static ssize_t kvm_htab_write(struct file *file, const char __user *buf,
>   				goto out;
>   			}
>   			if (!rma_setup && is_vrma_hpte(v)) {
> -				unsigned long psize = hpte_page_size(v, r);
> +				unsigned long psize = hpte_base_page_size(v, r);
>   				unsigned long senc = slb_pgsize_encoding(psize);
>   				unsigned long lpcr;
>   
> diff --git a/arch/powerpc/kvm/book3s_hv_rm_mmu.c b/arch/powerpc/kvm/book3s_hv_rm_mmu.c
> index 87624ab5ba82..c6aca75b8376 100644
> --- a/arch/powerpc/kvm/book3s_hv_rm_mmu.c
> +++ b/arch/powerpc/kvm/book3s_hv_rm_mmu.c
> @@ -839,7 +839,7 @@ long kvmppc_hv_find_lock_hpte(struct kvm *kvm, gva_t eaddr, unsigned long slb_v,
>   			 * to check against the actual page size.
>   			 */
>   			if ((v & valid) && (v & mask) == val &&
> -			    hpte_page_size(v, r) == (1ul << pshift))
> +			    hpte_base_page_size(v, r) == (1ul << pshift))
>   				/* Return with the HPTE still locked */
>   				return (hash << 3) + (i >> 1);
>