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KVM: PPC: Revert "KVM: PPC: Use kernel hash function"

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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 <agraf@suse.de>
This commit is contained in:
Alexander Graf 2010-08-02 21:48:53 +02:00 committed by Avi Kivity
parent 928d78be54
commit b9877ce299
2 changed files with 17 additions and 4 deletions
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10
arch/powerpc/kvm/book3s_32_mmu_host.c
View file

@ -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));
}

11
arch/powerpc/kvm/book3s_64_mmu_host.c
View file

@ -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;