Subject: Re: [PATCH kernel 3/4] KVM: PPC: Add @offset to kvmppc_spapr_tce_table

From: David Gibson <[email-masked]>
Date: Mon, 25 Jan 2016 16:33:09 +1100

On Thu, Jan 21, 2016 at 07:15:25PM +1100, Alexey Kardashevskiy wrote:
> This enables userspace view of TCE tables to start from non-zero offset
> on a bus. This will be used for huge DMA windows.

Again I'd like the commit message adjusted to clarify the fact that
this has internal changes only which will need interface changes to
actually use.

> Signed-off-by: Alexey Kardashevskiy <[email-masked]>

Reviewed-by: David Gibson <[email-masked]>

> ---
>  arch/powerpc/include/asm/kvm_host.h | 1 +
>  arch/powerpc/kvm/book3s_64_vio_hv.c | 6 ++++--
>  2 files changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/powerpc/include/asm/kvm_host.h b/arch/powerpc/include/asm/kvm_host.h
> index a4ed9f5..8769f91 100644
> --- a/arch/powerpc/include/asm/kvm_host.h
> +++ b/arch/powerpc/include/asm/kvm_host.h
> @@ -185,6 +185,7 @@ struct kvmppc_spapr_tce_table {
>  	u64 liobn;
>  	struct rcu_head rcu;
>  	u32 page_shift;
> +	u64 offset;		/* in pages */
>  	u64 size;		/* in pages */
>  	struct page *pages[0];
>  };
> diff --git a/arch/powerpc/kvm/book3s_64_vio_hv.c b/arch/powerpc/kvm/book3s_64_vio_hv.c
> index 01ef9f9..0e66459 100644
> --- a/arch/powerpc/kvm/book3s_64_vio_hv.c
> +++ b/arch/powerpc/kvm/book3s_64_vio_hv.c
> @@ -75,7 +75,8 @@ long kvmppc_ioba_validate(struct kvmppc_spapr_tce_table *stt,
>  	unsigned long mask = ~((1ULL << stt->page_shift) - 1);
>  	unsigned long idx = ioba >> stt->page_shift;
>  
> -	if ((ioba & ~mask) || (idx + npages > stt->size))
> +	if ((ioba & ~mask) || (idx < stt->offset) ||
> +			(idx - stt->offset + npages > stt->size))
>  		return H_PARAMETER;
>  
>  	return H_SUCCESS;
> @@ -147,6 +148,7 @@ void kvmppc_tce_put(struct kvmppc_spapr_tce_table *stt,
>  	struct page *page;
>  	u64 *tbl;
>  
> +	idx -= stt->offset;
>  	page = stt->pages[idx / TCES_PER_PAGE];
>  	tbl = kvmppc_page_address(page);
>  
> @@ -324,7 +326,7 @@ long kvmppc_h_get_tce(struct kvm_vcpu *vcpu, unsigned long liobn,
>  	if (ret != H_SUCCESS)
>  		return ret;
>  
> -	idx = ioba >> stt->page_shift;
> +	idx = (ioba >> stt->page_shift) - stt->offset;
>  	page = stt->pages[idx / TCES_PER_PAGE];
>  	tbl = (u64 *)page_address(page);
>  

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson