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Subject[PATCH v5 8/9] KVM: MMU: combine guest pte read between fetch and pte prefetch
Combine guest pte read between guest pte check in the fetch path and pte prefetch

Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
---
arch/x86/kvm/paging_tmpl.h | 69 ++++++++++++++++++++++++++-----------------
1 files changed, 42 insertions(+), 27 deletions(-)

diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h
index e04c1a4..a1e6d91 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;
@@ -291,12 +292,12 @@ 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 +312,7 @@ 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;
@@ -366,6 +359,35 @@ static void FNAME(pte_prefetch)(struct kvm_vcpu *vcpu, u64 *sptep)
}
}

+static bool FNAME(check_gpte_level)(struct kvm_vcpu *vcpu,
+ struct guest_walker *gw, int level)
+{
+ pt_element_t curr_pte;
+ int index, ret;
+ u64 mask;
+ gpa_t base_gpa, pte_gpa = gw->pte_gpa[level - 1];
+
+ if (level < gw->level)
+ return true;
+
+ if (level == PT_PAGE_TABLE_LEVEL) {
+ mask = PTE_PREFETCH_NUM * sizeof(pt_element_t) - 1;
+ base_gpa = pte_gpa & ~mask;
+ index = (pte_gpa - base_gpa) / sizeof(pt_element_t);
+
+ ret = kvm_read_guest_atomic(vcpu->kvm, base_gpa,
+ gw->prefetch_ptes, sizeof(gw->prefetch_ptes));
+ curr_pte = gw->prefetch_ptes[index];
+ } else
+ ret = kvm_read_guest_atomic(vcpu->kvm, pte_gpa, &curr_pte,
+ sizeof(curr_pte));
+
+ if (ret || curr_pte != gw->ptes[level - 1])
+ return false;
+
+ return true;
+}
+
/*
* Fetch a shadow pte for a specific level in the paging hierarchy.
*/
@@ -379,11 +401,9 @@ static u64 *FNAME(fetch)(struct kvm_vcpu *vcpu, gva_t addr,
u64 spte, *sptep = NULL;
int direct;
gfn_t table_gfn;
- int r;
int level;
bool dirty = is_dirty_gpte(gw->ptes[gw->level - 1]);
unsigned direct_access;
- pt_element_t curr_pte;
struct kvm_shadow_walk_iterator iterator;

if (!is_present_gpte(gw->ptes[gw->level - 1]))
@@ -449,17 +469,12 @@ static u64 *FNAME(fetch)(struct kvm_vcpu *vcpu, gva_t addr,
sp = kvm_mmu_get_page(vcpu, table_gfn, addr, level-1,
direct, access, sptep);
check_set_spte:
- if (level >= gw->level) {
- r = kvm_read_guest_atomic(vcpu->kvm,
- gw->pte_gpa[level - 1],
- &curr_pte, sizeof(curr_pte));
- if (r || curr_pte != gw->ptes[level - 1]) {
- if (nonpresent)
- kvm_mmu_put_page(sp, sptep);
- kvm_release_pfn_clean(pfn);
- sptep = NULL;
- break;
- }
+ if (!FNAME(check_gpte_level)(vcpu, gw, level)) {
+ if (nonpresent)
+ kvm_mmu_put_page(sp, sptep);
+ kvm_release_pfn_clean(pfn);
+ sptep = NULL;
+ break;
}

if (nonpresent) {
@@ -476,7 +491,7 @@ check_set_spte:
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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