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Date: Wed, 20 Oct 2021 00:32:12 +0900
From: Sergey Senozhatsky <senozhatsky@...omium.org>
To: Paolo Bonzini <pbonzini@...hat.com>,
David Matlack <dmatlack@...gle.com>
Cc: Sean Christopherson <seanjc@...gle.com>,
Vitaly Kuznetsov <vkuznets@...hat.com>,
Wanpeng Li <wanpengli@...cent.com>,
Jim Mattson <jmattson@...gle.com>,
Joerg Roedel <joro@...tes.org>,
Suleiman Souhlal <suleiman@...gle.com>, kvm@...r.kernel.org,
linux-kernel@...r.kernel.org,
Sergey Senozhatsky <senozhatsky@...omium.org>
Subject: [PATCHV2 1/3] KVM: x86: introduce kvm_mmu_pte_prefetch structure
kvm_mmu_pte_prefetch is a per-VCPU structure that holds a PTE
prefetch pages array, lock and the number of PTE to prefetch.
This is needed to turn PTE_PREFETCH_NUM into a tunable VM
parameter.
Signed-off-by: Sergey Senozhatsky <senozhatsky@...omium.org>
---
arch/x86/include/asm/kvm_host.h | 12 +++++++
arch/x86/kvm/mmu.h | 4 +++
arch/x86/kvm/mmu/mmu.c | 57 ++++++++++++++++++++++++++++++---
arch/x86/kvm/x86.c | 9 +++++-
4 files changed, 77 insertions(+), 5 deletions(-)
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 5271fce6cd65..11400bc3c70d 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -607,6 +607,16 @@ struct kvm_vcpu_xen {
u64 runstate_times[4];
};
+struct kvm_mmu_pte_prefetch {
+ /*
+ * This will be cast either to array of pointers to struct page,
+ * or array of u64, or array of u32
+ */
+ void *ents;
+ unsigned int num_ents;
+ spinlock_t lock;
+};
+
struct kvm_vcpu_arch {
/*
* rip and regs accesses must go through
@@ -682,6 +692,8 @@ struct kvm_vcpu_arch {
struct kvm_mmu_memory_cache mmu_gfn_array_cache;
struct kvm_mmu_memory_cache mmu_page_header_cache;
+ struct kvm_mmu_pte_prefetch mmu_pte_prefetch;
+
/*
* QEMU userspace and the guest each have their own FPU state.
* In vcpu_run, we switch between the user and guest FPU contexts.
diff --git a/arch/x86/kvm/mmu.h b/arch/x86/kvm/mmu.h
index 75367af1a6d3..b953a3a4083a 100644
--- a/arch/x86/kvm/mmu.h
+++ b/arch/x86/kvm/mmu.h
@@ -68,6 +68,10 @@ static __always_inline u64 rsvd_bits(int s, int e)
void kvm_mmu_set_mmio_spte_mask(u64 mmio_value, u64 mmio_mask, u64 access_mask);
void kvm_mmu_set_ept_masks(bool has_ad_bits, bool has_exec_only);
+int kvm_set_pte_prefetch(struct kvm_vcpu *vcpu, u64 num_ents);
+int kvm_init_pte_prefetch(struct kvm_vcpu *vcpu);
+void kvm_pte_prefetch_destroy(struct kvm_vcpu *vcpu);
+
void kvm_init_mmu(struct kvm_vcpu *vcpu);
void kvm_init_shadow_npt_mmu(struct kvm_vcpu *vcpu, unsigned long cr0,
unsigned long cr4, u64 efer, gpa_t nested_cr3);
diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 24a9f4c3f5e7..fed3a498a729 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -115,6 +115,7 @@ module_param(dbg, bool, 0644);
#endif
#define PTE_PREFETCH_NUM 8
+#define MAX_PTE_PREFETCH_NUM 128
#define PT32_LEVEL_BITS 10
@@ -732,7 +733,7 @@ static int mmu_topup_memory_caches(struct kvm_vcpu *vcpu, bool maybe_indirect)
/* 1 rmap, 1 parent PTE per level, and the prefetched rmaps. */
r = kvm_mmu_topup_memory_cache(&vcpu->arch.mmu_pte_list_desc_cache,
- 1 + PT64_ROOT_MAX_LEVEL + PTE_PREFETCH_NUM);
+ 1 + PT64_ROOT_MAX_LEVEL + MAX_PTE_PREFETCH_NUM);
if (r)
return r;
r = kvm_mmu_topup_memory_cache(&vcpu->arch.mmu_shadow_page_cache,
@@ -2753,12 +2754,13 @@ static int direct_pte_prefetch_many(struct kvm_vcpu *vcpu,
struct kvm_mmu_page *sp,
u64 *start, u64 *end)
{
- struct page *pages[PTE_PREFETCH_NUM];
+ struct page **pages;
struct kvm_memory_slot *slot;
unsigned int access = sp->role.access;
int i, ret;
gfn_t gfn;
+ pages = (struct page **)vcpu->arch.mmu_pte_prefetch.ents;
gfn = kvm_mmu_page_get_gfn(sp, start - sp->spt);
slot = gfn_to_memslot_dirty_bitmap(vcpu, gfn, access & ACC_WRITE_MASK);
if (!slot)
@@ -2781,14 +2783,17 @@ static void __direct_pte_prefetch(struct kvm_vcpu *vcpu,
struct kvm_mmu_page *sp, u64 *sptep)
{
u64 *spte, *start = NULL;
+ unsigned int pte_prefetch_num;
int i;
WARN_ON(!sp->role.direct);
- i = (sptep - sp->spt) & ~(PTE_PREFETCH_NUM - 1);
+ spin_lock(&vcpu->arch.mmu_pte_prefetch.lock);
+ pte_prefetch_num = vcpu->arch.mmu_pte_prefetch.num_ents;
+ i = (sptep - sp->spt) & ~(pte_prefetch_num - 1);
spte = sp->spt + i;
- for (i = 0; i < PTE_PREFETCH_NUM; i++, spte++) {
+ for (i = 0; i < pte_prefetch_num; i++, spte++) {
if (is_shadow_present_pte(*spte) || spte == sptep) {
if (!start)
continue;
@@ -2800,6 +2805,7 @@ static void __direct_pte_prefetch(struct kvm_vcpu *vcpu,
}
if (start)
direct_pte_prefetch_many(vcpu, sp, start, spte);
+ spin_unlock(&vcpu->arch.mmu_pte_prefetch.lock);
}
static void direct_pte_prefetch(struct kvm_vcpu *vcpu, u64 *sptep)
@@ -4914,6 +4920,49 @@ void kvm_init_mmu(struct kvm_vcpu *vcpu)
}
EXPORT_SYMBOL_GPL(kvm_init_mmu);
+int kvm_set_pte_prefetch(struct kvm_vcpu *vcpu, u64 num_ents)
+{
+ u64 *ents;
+
+ if (!num_ents)
+ return -EINVAL;
+
+ if (!is_power_of_2(num_ents))
+ return -EINVAL;
+
+ if (num_ents > MAX_PTE_PREFETCH_NUM)
+ return -EINVAL;
+
+ ents = kmalloc_array(num_ents, sizeof(u64), GFP_KERNEL);
+ if (!ents)
+ return -ENOMEM;
+
+ spin_lock(&vcpu->arch.mmu_pte_prefetch.lock);
+ kfree(vcpu->arch.mmu_pte_prefetch.ents);
+ vcpu->arch.mmu_pte_prefetch.ents = ents;
+ vcpu->arch.mmu_pte_prefetch.num_ents = num_ents;
+ spin_unlock(&vcpu->arch.mmu_pte_prefetch.lock);
+
+ return 0;
+}
+EXPORT_SYMBOL_GPL(kvm_set_pte_prefetch);
+
+int kvm_init_pte_prefetch(struct kvm_vcpu *vcpu)
+{
+ spin_lock_init(&vcpu->arch.mmu_pte_prefetch.lock);
+
+ return kvm_set_pte_prefetch(vcpu, PTE_PREFETCH_NUM);
+}
+EXPORT_SYMBOL_GPL(kvm_init_pte_prefetch);
+
+void kvm_pte_prefetch_destroy(struct kvm_vcpu *vcpu)
+{
+ vcpu->arch.mmu_pte_prefetch.num_ents = 0;
+ kfree(vcpu->arch.mmu_pte_prefetch.ents);
+ vcpu->arch.mmu_pte_prefetch.ents = NULL;
+}
+EXPORT_SYMBOL_GPL(kvm_pte_prefetch_destroy);
+
static union kvm_mmu_page_role
kvm_mmu_calc_root_page_role(struct kvm_vcpu *vcpu)
{
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index b0f99132d7d1..4805960a89e6 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -10707,10 +10707,14 @@ int kvm_arch_vcpu_create(struct kvm_vcpu *vcpu)
vcpu->arch.hv_root_tdp = INVALID_PAGE;
#endif
- r = static_call(kvm_x86_vcpu_create)(vcpu);
+ r = kvm_init_pte_prefetch(vcpu);
if (r)
goto free_guest_fpu;
+ r = static_call(kvm_x86_vcpu_create)(vcpu);
+ if (r)
+ goto free_pte_prefetch;
+
vcpu->arch.arch_capabilities = kvm_get_arch_capabilities();
vcpu->arch.msr_platform_info = MSR_PLATFORM_INFO_CPUID_FAULT;
kvm_vcpu_mtrr_init(vcpu);
@@ -10721,6 +10725,8 @@ int kvm_arch_vcpu_create(struct kvm_vcpu *vcpu)
vcpu_put(vcpu);
return 0;
+free_pte_prefetch:
+ kvm_pte_prefetch_destroy(vcpu);
free_guest_fpu:
kvm_free_guest_fpu(vcpu);
free_user_fpu:
@@ -10782,6 +10788,7 @@ void kvm_arch_vcpu_destroy(struct kvm_vcpu *vcpu)
kvm_free_lapic(vcpu);
idx = srcu_read_lock(&vcpu->kvm->srcu);
kvm_mmu_destroy(vcpu);
+ kvm_pte_prefetch_destroy(vcpu);
srcu_read_unlock(&vcpu->kvm->srcu, idx);
free_page((unsigned long)vcpu->arch.pio_data);
kvfree(vcpu->arch.cpuid_entries);
--
2.33.0.1079.g6e70778dc9-goog
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