Re: [PATCH 2/2] kvm: powerpc: set cache coherency only for kernel managed pages

["\"“tiejun.chen”\"" <tiejun.chen@windriver.com>]

On 07/18/2013 02:04 PM, Bharat Bhushan wrote:
> If there is a struct page for the requested mapping then it's
> normal DDR and the mapping sets "M" bit (coherent, cacheable)
> else this is treated as I/O and we set  "I + G"  (cache inhibited, guarded)
>
> This helps setting proper TLB mapping for direct assigned device
>
> Signed-off-by: Bharat Bhushan <bharat.bhushan@freescale.com>
> ---
>   arch/powerpc/kvm/e500_mmu_host.c |   17 ++++++++++++-----
>   1 files changed, 12 insertions(+), 5 deletions(-)
>
> diff --git a/arch/powerpc/kvm/e500_mmu_host.c b/arch/powerpc/kvm/e500_mmu_host.c
> index 1c6a9d7..089c227 100644
> --- a/arch/powerpc/kvm/e500_mmu_host.c
> +++ b/arch/powerpc/kvm/e500_mmu_host.c
> @@ -64,13 +64,20 @@ static inline u32 e500_shadow_mas3_attrib(u32 mas3, int usermode)
>   	return mas3;
>   }
>
> -static inline u32 e500_shadow_mas2_attrib(u32 mas2, int usermode)
> +static inline u32 e500_shadow_mas2_attrib(u32 mas2, pfn_t pfn)
>   {
> +	u32 mas2_attr;
> +
> +	mas2_attr = mas2 & MAS2_ATTRIB_MASK;
> +
> +	if (!pfn_valid(pfn)) {
> +		mas2_attr |= MAS2_I | MAS2_G;
> +	} else {
>   #ifdef CONFIG_SMP
> -	return (mas2 & MAS2_ATTRIB_MASK) | MAS2_M;
> -#else
> -	return mas2 & MAS2_ATTRIB_MASK;
> +		mas2_attr |= MAS2_M;
>   #endif
> +	}

Additionally, in UP case this little chunk of code is equivalent to

	if (1) {
		mas2_attr |= MAS2_I | MAS2_G;
	} else {
	}

So you'd better wrapper MAS2_m in advance like,

#ifdef CONFIG_SMP
#define M_IF_SMP        MAS2_M
#else
#define M_IF_SMP        0
#endif

Then	
	if (1)
		mas2_attr |= MAS2_I | MAS2_G;
	else
		mas2_attr |= M_IF_SMP;

Tiejun

> +	return mas2_attr;
>   }
>
>   /*
> @@ -313,7 +320,7 @@ static void kvmppc_e500_setup_stlbe(
>   	/* Force IPROT=0 for all guest mappings. */
>   	stlbe->mas1 = MAS1_TSIZE(tsize) | get_tlb_sts(gtlbe) | MAS1_VALID;
>   	stlbe->mas2 = (gvaddr & MAS2_EPN) |
> -		      e500_shadow_mas2_attrib(gtlbe->mas2, pr);
> +		      e500_shadow_mas2_attrib(gtlbe->mas2, pfn);
>   	stlbe->mas7_3 = ((u64)pfn << PAGE_SHIFT) |
>   			e500_shadow_mas3_attrib(gtlbe->mas7_3, pr);
>
>