From b9877ce2994cc812f00dbb2adb88c1749b6dac86 Mon Sep 17 00:00:00 2001 From: Alexander Graf Date: Mon, 2 Aug 2010 21:48:53 +0200 Subject: [PATCH] KVM: PPC: Revert "KVM: PPC: Use kernel hash function" It turns out the in-kernel hash function is sub-optimal for our subtle hash inputs where every bit is significant. So let's revert to the original hash functions. This reverts commit 05340ab4f9a6626f7a2e8f9fe5397c61d494f445. Signed-off-by: Alexander Graf --- arch/powerpc/kvm/book3s_32_mmu_host.c | 10 ++++++++-- arch/powerpc/kvm/book3s_64_mmu_host.c | 11 +++++++++-- 2 files changed, 17 insertions(+), 4 deletions(-) diff --git a/arch/powerpc/kvm/book3s_32_mmu_host.c b/arch/powerpc/kvm/book3s_32_mmu_host.c index 343452c..57dddeb 100644 --- a/arch/powerpc/kvm/book3s_32_mmu_host.c +++ b/arch/powerpc/kvm/book3s_32_mmu_host.c @@ -19,7 +19,6 @@ */ #include -#include #include #include @@ -77,7 +76,14 @@ void kvmppc_mmu_invalidate_pte(struct kvm_vcpu *vcpu, struct hpte_cache *pte) * a hash, so we don't waste cycles on looping */ static u16 kvmppc_sid_hash(struct kvm_vcpu *vcpu, u64 gvsid) { - return hash_64(gvsid, SID_MAP_BITS); + return (u16)(((gvsid >> (SID_MAP_BITS * 7)) & SID_MAP_MASK) ^ + ((gvsid >> (SID_MAP_BITS * 6)) & SID_MAP_MASK) ^ + ((gvsid >> (SID_MAP_BITS * 5)) & SID_MAP_MASK) ^ + ((gvsid >> (SID_MAP_BITS * 4)) & SID_MAP_MASK) ^ + ((gvsid >> (SID_MAP_BITS * 3)) & SID_MAP_MASK) ^ + ((gvsid >> (SID_MAP_BITS * 2)) & SID_MAP_MASK) ^ + ((gvsid >> (SID_MAP_BITS * 1)) & SID_MAP_MASK) ^ + ((gvsid >> (SID_MAP_BITS * 0)) & SID_MAP_MASK)); } diff --git a/arch/powerpc/kvm/book3s_64_mmu_host.c b/arch/powerpc/kvm/book3s_64_mmu_host.c index 321c931..e7c4d00 100644 --- a/arch/powerpc/kvm/book3s_64_mmu_host.c +++ b/arch/powerpc/kvm/book3s_64_mmu_host.c @@ -20,7 +20,6 @@ */ #include -#include #include #include @@ -44,9 +43,17 @@ void kvmppc_mmu_invalidate_pte(struct kvm_vcpu *vcpu, struct hpte_cache *pte) * a hash, so we don't waste cycles on looping */ static u16 kvmppc_sid_hash(struct kvm_vcpu *vcpu, u64 gvsid) { - return hash_64(gvsid, SID_MAP_BITS); + return (u16)(((gvsid >> (SID_MAP_BITS * 7)) & SID_MAP_MASK) ^ + ((gvsid >> (SID_MAP_BITS * 6)) & SID_MAP_MASK) ^ + ((gvsid >> (SID_MAP_BITS * 5)) & SID_MAP_MASK) ^ + ((gvsid >> (SID_MAP_BITS * 4)) & SID_MAP_MASK) ^ + ((gvsid >> (SID_MAP_BITS * 3)) & SID_MAP_MASK) ^ + ((gvsid >> (SID_MAP_BITS * 2)) & SID_MAP_MASK) ^ + ((gvsid >> (SID_MAP_BITS * 1)) & SID_MAP_MASK) ^ + ((gvsid >> (SID_MAP_BITS * 0)) & SID_MAP_MASK)); } + static struct kvmppc_sid_map *find_sid_vsid(struct kvm_vcpu *vcpu, u64 gvsid) { struct kvmppc_sid_map *map; -- 2.7.4