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Subject[PATCH v4 6/6] KVM: MMU: trace pte prefetch
Trace pte prefetch, it can help us to improve the prefetch's performance

Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
---
arch/x86/kvm/mmu.c | 41 +++++++++++++++++++++++++++++++----------
arch/x86/kvm/mmutrace.h | 33 +++++++++++++++++++++++++++++++++
arch/x86/kvm/paging_tmpl.h | 23 +++++++++++++++++------
3 files changed, 81 insertions(+), 16 deletions(-)
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 00f8ae9..71a694e 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -91,6 +91,12 @@ module_param(oos_shadow, bool, 0644);

#define PTE_PREFETCH_NUM 16

+#define PREFETCH_SUCCESS 0
+#define PREFETCH_ERR_GFN2PFN 1
+#define PREFETCH_ERR_ALLOC_MEM 2
+#define PREFETCH_ERR_RSVD_BITS_SET 3
+#define PREFETCH_ERR_MMIO 4
+
#define PT_FIRST_AVAIL_BITS_SHIFT 9
#define PT64_SECOND_AVAIL_BITS_SHIFT 52

@@ -2004,7 +2010,7 @@ static void nonpaging_new_cr3(struct kvm_vcpu *vcpu)

static int direct_pte_prefetch_many(struct kvm_vcpu *vcpu,
struct kvm_mmu_page *sp,
- u64 *start, u64 *end)
+ u64 *start, u64 *end, u64 address)
{
gfn_t gfn;
struct page *pages[PTE_PREFETCH_NUM];
@@ -2016,31 +2022,44 @@ static int direct_pte_prefetch_many(struct kvm_vcpu *vcpu,

ret = gfn_to_page_many_atomic(vcpu->kvm, gfn, pages,
end - start, &enough);
- if (ret <= 0)
+ if (ret <= 0) {
+ trace_pte_prefetch(true, address, 0, ret == -1 ?
+ PREFETCH_ERR_MMIO : PREFETCH_ERR_GFN2PFN);
return -1;
+ }

- for (j = 0; j < ret; j++, gfn++, start++)
+ for (j = 0; j < ret; j++, gfn++, start++) {
+ trace_pte_prefetch(true, address, 0,
+ PREFETCH_SUCCESS);
mmu_set_spte(vcpu, start, ACC_ALL,
sp->role.access, 0, 0, 1, NULL,
sp->role.level, gfn,
page_to_pfn(pages[j]), true, true);
+ }

- if (!enough)
+ if (!enough) {
+ trace_pte_prefetch(true, address, 0,
+ PREFETCH_ERR_GFN2PFN);
return -1;
+ }
}
return 0;
}

static void __direct_pte_prefetch(struct kvm_vcpu *vcpu,
- struct kvm_mmu_page *sp, u64 *sptep)
+ struct kvm_mmu_page *sp, u64 *sptep,
+ u64 addr)
{
u64 *start = NULL;
int index, i, max;

WARN_ON(!sp->role.direct);

- if (pte_prefetch_topup_memory_cache(vcpu))
+ if (pte_prefetch_topup_memory_cache(vcpu)) {
+ trace_pte_prefetch(true, addr, 0,
+ PREFETCH_ERR_ALLOC_MEM);
return;
+ }

index = sptep - sp->spt;
i = index & ~(PTE_PREFETCH_NUM - 1);
@@ -2052,7 +2071,8 @@ static void __direct_pte_prefetch(struct kvm_vcpu *vcpu,
if (*spte != shadow_trap_nonpresent_pte || spte == sptep) {
if (!start)
continue;
- if (direct_pte_prefetch_many(vcpu, sp, start, spte) < 0)
+ if (direct_pte_prefetch_many(vcpu, sp, start, spte,
+ addr) < 0)
break;
start = NULL;
} else if (!start)
@@ -2060,7 +2080,7 @@ static void __direct_pte_prefetch(struct kvm_vcpu *vcpu,
}
}

-static void direct_pte_prefetch(struct kvm_vcpu *vcpu, u64 *sptep)
+static void direct_pte_prefetch(struct kvm_vcpu *vcpu, u64 *sptep, u64 addr)
{
struct kvm_mmu_page *sp;

@@ -2077,7 +2097,7 @@ static void direct_pte_prefetch(struct kvm_vcpu *vcpu, u64 *sptep)
if (sp->role.level > PT_PAGE_TABLE_LEVEL)
return;

- __direct_pte_prefetch(vcpu, sp, sptep);
+ __direct_pte_prefetch(vcpu, sp, sptep, addr);
}

static int __direct_map(struct kvm_vcpu *vcpu, gpa_t v, int write,
@@ -2093,7 +2113,8 @@ static int __direct_map(struct kvm_vcpu *vcpu, gpa_t v, int write,
mmu_set_spte(vcpu, iterator.sptep, ACC_ALL, ACC_ALL,
0, write, 1, &pt_write,
level, gfn, pfn, false, true);
- direct_pte_prefetch(vcpu, iterator.sptep);
+ direct_pte_prefetch(vcpu, iterator.sptep,
+ gfn << PAGE_SHIFT);
++vcpu->stat.pf_fixed;
break;
}
diff --git a/arch/x86/kvm/mmutrace.h b/arch/x86/kvm/mmutrace.h
index 3aab0f0..c07b6a6 100644
--- a/arch/x86/kvm/mmutrace.h
+++ b/arch/x86/kvm/mmutrace.h
@@ -195,6 +195,39 @@ DEFINE_EVENT(kvm_mmu_page_class, kvm_mmu_prepare_zap_page,

TP_ARGS(sp)
);
+
+#define pte_prefetch_err \
+ {PREFETCH_SUCCESS, "SUCCESS" }, \
+ {PREFETCH_ERR_GFN2PFN, "ERR_GFN2PFN" }, \
+ {PREFETCH_ERR_ALLOC_MEM, "ERR_ALLOC_MEM" }, \
+ {PREFETCH_ERR_RSVD_BITS_SET, "ERR_RSVD_BITS_SET"}, \
+ {PREFETCH_ERR_MMIO, "ERR_MMIO" }
+
+TRACE_EVENT(
+ pte_prefetch,
+ TP_PROTO(bool direct, u64 addr, u64 gpte, int err_code),
+
+ TP_ARGS(direct, addr, gpte, err_code),
+
+ TP_STRUCT__entry(
+ __field(bool, direct)
+ __field(u64, addr)
+ __field(u64, gpte)
+ __field(int, err_code)
+ ),
+
+ TP_fast_assign(
+ __entry->direct = direct;
+ __entry->addr = addr;
+ __entry->gpte = gpte;
+ __entry->err_code = err_code;
+ ),
+
+ TP_printk("%s address:%llx gpte:%llx %s",
+ __entry->direct ? "direct" : "indirect",
+ __entry->addr, __entry->gpte,
+ __print_symbolic(__entry->err_code, pte_prefetch_err))
+ );
#endif /* _TRACE_KVMMMU_H */

#undef TRACE_INCLUDE_PATH
diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h
index 509af1a..b5ca8dd 100644
--- a/arch/x86/kvm/paging_tmpl.h
+++ b/arch/x86/kvm/paging_tmpl.h
@@ -318,7 +318,7 @@ static void FNAME(update_pte)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp,
}

static void FNAME(pte_prefetch)(struct kvm_vcpu *vcpu,
- struct guest_walker *gw, u64 *sptep)
+ struct guest_walker *gw, u64 *sptep, u64 addr)
{
struct kvm_mmu_page *sp;
pt_element_t *gptep;
@@ -331,7 +331,7 @@ static void FNAME(pte_prefetch)(struct kvm_vcpu *vcpu,
return;

if (sp->role.direct)
- return __direct_pte_prefetch(vcpu, sp, sptep);
+ return __direct_pte_prefetch(vcpu, sp, sptep, addr);

index = sptep - sp->spt;
i = index & ~(PTE_PREFETCH_NUM - 1);
@@ -339,8 +339,10 @@ static void FNAME(pte_prefetch)(struct kvm_vcpu *vcpu,

gptep = gw->prefetch_ptes;

- if (pte_prefetch_topup_memory_cache(vcpu))
+ if (pte_prefetch_topup_memory_cache(vcpu)) {
+ trace_pte_prefetch(false, addr, 0, PREFETCH_ERR_ALLOC_MEM);
return;
+ }

for (j = 0; i < max; i++, j++) {
pt_element_t gpte;
@@ -357,15 +359,21 @@ static void FNAME(pte_prefetch)(struct kvm_vcpu *vcpu,

gpte = gptep[j];

- if (is_rsvd_bits_set(vcpu, gpte, PT_PAGE_TABLE_LEVEL))
+ if (is_rsvd_bits_set(vcpu, gpte, PT_PAGE_TABLE_LEVEL)) {
+ trace_pte_prefetch(false, addr, gpte,
+ PREFETCH_ERR_RSVD_BITS_SET);
break;
+ }

if (!(gpte & PT_ACCESSED_MASK))
continue;

if (!is_present_gpte(gpte)) {
- if (!sp->unsync)
+ if (!sp->unsync) {
+ trace_pte_prefetch(false, addr, gpte,
+ PREFETCH_SUCCESS);
__set_spte(spte, shadow_notrap_nonpresent_pte);
+ }
continue;
}

@@ -373,10 +381,13 @@ static void FNAME(pte_prefetch)(struct kvm_vcpu *vcpu,

pfn = gfn_to_pfn_atomic(vcpu->kvm, gfn);
if (is_error_pfn(pfn)) {
+ trace_pte_prefetch(false, addr, gpte,
+ PREFETCH_ERR_GFN2PFN);
kvm_release_pfn_clean(pfn);
break;
}

+ trace_pte_prefetch(false, addr, gpte, PREFETCH_SUCCESS);
pte_access = sp->role.access & FNAME(gpte_access)(vcpu, gpte);
mmu_set_spte(vcpu, spte, sp->role.access, pte_access, 0, 0,
is_dirty_gpte(gpte), NULL, sp->role.level, gfn,
@@ -420,7 +431,7 @@ static u64 *FNAME(fetch)(struct kvm_vcpu *vcpu, gva_t addr,
user_fault, write_fault,
dirty, ptwrite, level,
gw->gfn, pfn, false, true);
- FNAME(pte_prefetch)(vcpu, gw, sptep);
+ FNAME(pte_prefetch)(vcpu, gw, sptep, addr);
break;
}

--
1.6.1.2



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