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

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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@xxxxxxxxxxxxx>
---
  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);



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