[PATCH] kvm, x86: simplify manipulation of ASYNC_PF_PER_VCPU on x86

[Wei Yang <richardw.yang@xxxxxxxxxxxxxxx>]

In generic code kvm_setup_async_pf() checks the async_pf size by:

    if (vcpu->async_pf.queued >= ASYNC_PF_PER_VCPU)

While in x86, we define the array as:

    gfn_t gfns[roundup_pow_of_two(ASYNC_PF_PER_VCPU)];

And each time we compare the index like this:

    i < roundup_pow_of_two(ASYNC_PF_PER_VCPU)

The behavior is correct now, while not consistent with generic code.

As for now ASYNC_PF_PER_VCPU is defined as 64, which is already a power of
2. This patch introduces ASYNC_PF_PER_VCPU_ORDER and rewrite the definition
as:

    #define ASYNC_PF_PER_VCPU_ORDER 6
    #define ASYNC_PF_PER_VCPU      (1 << ASYNC_PF_PER_VCPU_ORDER)

By doing so, we can remove the roundup_pow_of_two()/order_base_2() helpers
when access async_pf on x86. And this make code consistent between
generic and x86.

Signed-off-by: Wei Yang <richardw.yang@xxxxxxxxxxxxxxx>

---
v2: Radim suggest to change platform code instead of generic code.
---
 arch/x86/include/asm/kvm_host.h | 5 +++--
 arch/x86/kvm/x86.c              | 8 ++++----
 2 files changed, 7 insertions(+), 6 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index fbda5a917c5b..570ddc74a4e5 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -134,7 +134,8 @@ static inline gfn_t gfn_to_index(gfn_t gfn, gfn_t base_gfn, int level)
 #define KVM_NR_FIXED_MTRR_REGION 88
 #define KVM_NR_VAR_MTRR 8
 
-#define ASYNC_PF_PER_VCPU 64
+#define ASYNC_PF_PER_VCPU_ORDER 6
+#define ASYNC_PF_PER_VCPU (1 << ASYNC_PF_PER_VCPU_ORDER)
 
 enum kvm_reg {
 	VCPU_REGS_RAX = 0,
@@ -726,7 +727,7 @@ 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 d02937760c3b..ff5296cbc9da 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -218,7 +218,7 @@ 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;
 }
 
@@ -9488,12 +9488,12 @@ 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)
 {
-	return hash_32(gfn & 0xffffffff, order_base_2(ASYNC_PF_PER_VCPU));
+	return hash_32(gfn & 0xffffffff, ASYNC_PF_PER_VCPU_ORDER);
 }
 
 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)
@@ -9511,7 +9511,7 @@ 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);
-- 
2.19.1