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 <ag...@suse.de> --- 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 <linux/kvm_host.h> -#include <linux/hash.h> #include <asm/kvm_ppc.h> #include <asm/kvm_book3s.h> @@ -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 <linux/kvm_host.h> -#include <linux/hash.h> #include <asm/kvm_ppc.h> #include <asm/kvm_book3s.h> @@ -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; -- 1.6.0.2 -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html