From dd03bcaad0b1a62c8ea6297e6f2a5993c1c5cd30 Mon Sep 17 00:00:00 2001 From: Peter Xu Date: Thu, 16 Apr 2020 11:58:59 -0400 Subject: [PATCH] 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 Message-Id: <20200416155859.267366-1-peterx@redhat.com> Signed-off-by: Paolo Bonzini --- arch/x86/include/asm/kvm_host.h | 2 +- arch/x86/kvm/x86.c | 8 +++++--- 2 files changed, 6 insertions(+), 4 deletions(-) diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h index b8d035694b87..04f44961858b 100644 --- a/arch/x86/include/asm/kvm_host.h +++ b/arch/x86/include/asm/kvm_host.h @@ -763,7 +763,7 @@ struct kvm_vcpu_arch { struct { bool halted; - gfn_t gfns[roundup_pow_of_two(ASYNC_PF_PER_VCPU)]; + gfn_t gfns[ASYNC_PF_PER_VCPU]; struct gfn_to_hva_cache data; u64 msr_val; u32 id; 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); -- 2.20.1