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| author | Peter Xu <peterx@redhat.com> | 2020-04-16 11:58:59 -0400 |
|---|---|---|
| committer | Paolo Bonzini <pbonzini@redhat.com> | 2020-05-15 12:26:13 -0400 |
| commit | dd03bcaad0b1a62c8ea6297e6f2a5993c1c5cd30 (patch) | |
| tree | 58a3a8e50c197261712183bccff0da1c6623303f /arch/x86/kvm/x86.c | |
| parent | c16312f4fa75e786f5748a7b721a05e6b0d761fe (diff) | |
| download | lwn-dd03bcaad0b1a62c8ea6297e6f2a5993c1c5cd30.tar.gz lwn-dd03bcaad0b1a62c8ea6297e6f2a5993c1c5cd30.zip | |
KVM: X86: Force ASYNC_PF_PER_VCPU to be power of two
Forcing the ASYNC_PF_PER_VCPU to be power of two is much easier to be
used rather than calling roundup_pow_of_two() from time to time. Do
this by adding a BUILD_BUG_ON() inside the hash function.
Another point is that generally async pf does not allow concurrency
over ASYNC_PF_PER_VCPU after all (see kvm_setup_async_pf()), so it
does not make much sense either to have it not a power of two or some
of the entries will definitely be wasted.
Signed-off-by: Peter Xu <peterx@redhat.com>
Message-Id: <20200416155859.267366-1-peterx@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'arch/x86/kvm/x86.c')
| -rw-r--r-- | arch/x86/kvm/x86.c | 8 |
1 files changed, 5 insertions, 3 deletions
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index a52ef81fb87a..8e28f21fb39b 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -257,7 +257,7 @@ static int emulator_fix_hypercall(struct x86_emulate_ctxt *ctxt); static inline void kvm_async_pf_hash_reset(struct kvm_vcpu *vcpu) { int i; - for (i = 0; i < roundup_pow_of_two(ASYNC_PF_PER_VCPU); i++) + for (i = 0; i < ASYNC_PF_PER_VCPU; i++) vcpu->arch.apf.gfns[i] = ~0; } @@ -10310,12 +10310,14 @@ void kvm_arch_async_page_ready(struct kvm_vcpu *vcpu, struct kvm_async_pf *work) static inline u32 kvm_async_pf_hash_fn(gfn_t gfn) { + BUILD_BUG_ON(!is_power_of_2(ASYNC_PF_PER_VCPU)); + return hash_32(gfn & 0xffffffff, order_base_2(ASYNC_PF_PER_VCPU)); } static inline u32 kvm_async_pf_next_probe(u32 key) { - return (key + 1) & (roundup_pow_of_two(ASYNC_PF_PER_VCPU) - 1); + return (key + 1) & (ASYNC_PF_PER_VCPU - 1); } static void kvm_add_async_pf_gfn(struct kvm_vcpu *vcpu, gfn_t gfn) @@ -10333,7 +10335,7 @@ static u32 kvm_async_pf_gfn_slot(struct kvm_vcpu *vcpu, gfn_t gfn) int i; u32 key = kvm_async_pf_hash_fn(gfn); - for (i = 0; i < roundup_pow_of_two(ASYNC_PF_PER_VCPU) && + for (i = 0; i < ASYNC_PF_PER_VCPU && (vcpu->arch.apf.gfns[key] != gfn && vcpu->arch.apf.gfns[key] != ~0); i++) key = kvm_async_pf_next_probe(key); |