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Subject[PATCH 10/11] KVM: MMU: combine guest pte read between walk and pte prefetch
Combine guest pte read between guest pte walk and pte prefetch

Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
---
arch/x86/kvm/paging_tmpl.h | 48 ++++++++++++++++++++++++++++++-------------
1 files changed, 33 insertions(+), 15 deletions(-)
diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h
index d8c3be8..3e047b4 100644
--- a/arch/x86/kvm/paging_tmpl.h
+++ b/arch/x86/kvm/paging_tmpl.h
@@ -67,6 +67,7 @@ struct guest_walker {
int level;
gfn_t table_gfn[PT_MAX_FULL_LEVELS];
pt_element_t ptes[PT_MAX_FULL_LEVELS];
+ pt_element_t prefetch_ptes[PTE_PREFETCH_NUM];
gpa_t pte_gpa[PT_MAX_FULL_LEVELS];
unsigned pt_access;
unsigned pte_access;
@@ -110,6 +111,31 @@ static unsigned FNAME(gpte_access)(struct kvm_vcpu *vcpu, pt_element_t gpte)
return access;
}

+static int FNAME(read_guest_pte)(struct kvm_vcpu *vcpu,
+ struct guest_walker *walker,
+ gpa_t pte_gpa, pt_element_t *pte)
+{
+ int index, ret;
+ u64 mask;
+ gpa_t base_gpa;
+
+ if (walker->level > PT_PAGE_TABLE_LEVEL)
+ return kvm_read_guest(vcpu->kvm, pte_gpa, pte,
+ sizeof(*pte));
+
+ mask = PTE_PREFETCH_NUM * sizeof(*pte) - 1;
+ base_gpa = pte_gpa & ~mask;
+ index = (pte_gpa - base_gpa) / sizeof(*pte);
+
+ ret = kvm_read_guest(vcpu->kvm, base_gpa, walker->prefetch_ptes,
+ sizeof(walker->prefetch_ptes));
+ if (ret)
+ return ret;
+
+ *pte = walker->prefetch_ptes[index];
+ return 0;
+}
+
/*
* Fetch a guest pte for a guest virtual address
*/
@@ -151,7 +177,7 @@ walk:
walker->table_gfn[walker->level - 1] = table_gfn;
walker->pte_gpa[walker->level - 1] = pte_gpa;

- if (kvm_read_guest(vcpu->kvm, pte_gpa, &pte, sizeof(pte)))
+ if (FNAME(read_guest_pte)(vcpu, walker, pte_gpa, &pte))
goto not_present;

trace_kvm_mmu_paging_element(pte, walker->level);
@@ -291,12 +317,12 @@ static void FNAME(update_pte)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp,
gpte_to_gfn(gpte), pfn, true, true);
}

-static void FNAME(pte_prefetch)(struct kvm_vcpu *vcpu, u64 *sptep)
+static void FNAME(pte_prefetch)(struct kvm_vcpu *vcpu,
+ struct guest_walker *gw, u64 *sptep)
{
struct kvm_mmu_page *sp;
- pt_element_t gptep[PTE_PREFETCH_NUM];
- gpa_t first_pte_gpa;
- int offset = 0, index, i, j, max;
+ pt_element_t *gptep;
+ int index, i, j, max;

sp = page_header(__pa(sptep));
index = sptep - sp->spt;
@@ -311,15 +337,7 @@ static void FNAME(pte_prefetch)(struct kvm_vcpu *vcpu, u64 *sptep)
i = index & ~(PTE_PREFETCH_NUM - 1);
max = index | (PTE_PREFETCH_NUM - 1);

- if (PTTYPE == 32)
- offset = sp->role.quadrant << PT64_LEVEL_BITS;
-
- first_pte_gpa = gfn_to_gpa(sp->gfn) +
- (offset + i) * sizeof(pt_element_t);
-
- if (kvm_read_guest_atomic(vcpu->kvm, first_pte_gpa, gptep,
- sizeof(gptep)) < 0)
- return;
+ gptep = gw->prefetch_ptes;

if (pte_prefetch_topup_memory_cache(vcpu))
return;
@@ -402,7 +420,7 @@ 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, sptep);
+ FNAME(pte_prefetch)(vcpu, gw, sptep);
break;
}

--
1.6.1.2



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