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Subject[PATCH 05/15] KVM: MMU: optimize to handle dirty bit
If dirty bit is not set, we can make the pte access read-only to avoid handing
dirty bit everywhere

Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
---
arch/x86/kvm/mmu.c | 13 ++++++-------
arch/x86/kvm/paging_tmpl.h | 30 ++++++++++--------------------
2 files changed, 16 insertions(+), 27 deletions(-)

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 415030e..a10afd4 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -1923,7 +1923,7 @@ static int mmu_need_write_protect(struct kvm_vcpu *vcpu, gfn_t gfn,

static int set_spte(struct kvm_vcpu *vcpu, u64 *sptep,
unsigned pte_access, int user_fault,
- int write_fault, int dirty, int level,
+ int write_fault, int level,
gfn_t gfn, pfn_t pfn, bool speculative,
bool can_unsync, bool host_writable)
{
@@ -1938,8 +1938,7 @@ static int set_spte(struct kvm_vcpu *vcpu, u64 *sptep,
spte = PT_PRESENT_MASK;
if (!speculative)
spte |= shadow_accessed_mask;
- if (!dirty)
- pte_access &= ~ACC_WRITE_MASK;
+
if (pte_access & ACC_EXEC_MASK)
spte |= shadow_x_mask;
else
@@ -2014,7 +2013,7 @@ done:

static void mmu_set_spte(struct kvm_vcpu *vcpu, u64 *sptep,
unsigned pt_access, unsigned pte_access,
- int user_fault, int write_fault, int dirty,
+ int user_fault, int write_fault,
int *ptwrite, int level, gfn_t gfn,
pfn_t pfn, bool speculative,
bool host_writable)
@@ -2050,7 +2049,7 @@ static void mmu_set_spte(struct kvm_vcpu *vcpu, u64 *sptep,
}

if (set_spte(vcpu, sptep, pte_access, user_fault, write_fault,
- dirty, level, gfn, pfn, speculative, true,
+ level, gfn, pfn, speculative, true,
host_writable)) {
if (write_fault)
*ptwrite = 1;
@@ -2120,7 +2119,7 @@ static int direct_pte_prefetch_many(struct kvm_vcpu *vcpu,

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

@@ -2184,7 +2183,7 @@ static int __direct_map(struct kvm_vcpu *vcpu, gpa_t v, int write,
unsigned pte_access = ACC_ALL;

mmu_set_spte(vcpu, iterator.sptep, ACC_ALL, pte_access,
- 0, write, 1, &pt_write,
+ 0, write, &pt_write,
level, gfn, pfn, prefault, map_writable);
direct_pte_prefetch(vcpu, iterator.sptep);
++vcpu->stat.pf_fixed;
diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h
index b0c8184..67971da 100644
--- a/arch/x86/kvm/paging_tmpl.h
+++ b/arch/x86/kvm/paging_tmpl.h
@@ -106,6 +106,9 @@ static unsigned FNAME(gpte_access)(struct kvm_vcpu *vcpu, pt_element_t gpte)
unsigned access;

access = (gpte & (PT_WRITABLE_MASK | PT_USER_MASK)) | ACC_EXEC_MASK;
+ if (!is_dirty_gpte(gpte))
+ access &= ~ACC_WRITE_MASK;
+
#if PTTYPE == 64
if (vcpu->arch.mmu.nx)
access &= ~(gpte >> PT64_NX_SHIFT);
@@ -378,7 +381,7 @@ static void FNAME(update_pte)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp,
* vcpu->arch.update_pte.pfn was fetched from get_user_pages(write = 1).
*/
mmu_set_spte(vcpu, spte, sp->role.access, pte_access, 0, 0,
- is_dirty_gpte(gpte), NULL, PT_PAGE_TABLE_LEVEL,
+ NULL, PT_PAGE_TABLE_LEVEL,
gpte_to_gfn(gpte), pfn, true, true);
}

@@ -429,7 +432,6 @@ static void FNAME(pte_prefetch)(struct kvm_vcpu *vcpu, struct guest_walker *gw,
unsigned pte_access;
gfn_t gfn;
pfn_t pfn;
- bool dirty;

if (spte == sptep)
continue;
@@ -444,16 +446,15 @@ static void FNAME(pte_prefetch)(struct kvm_vcpu *vcpu, struct guest_walker *gw,

pte_access = sp->role.access & FNAME(gpte_access)(vcpu, gpte);
gfn = gpte_to_gfn(gpte);
- dirty = is_dirty_gpte(gpte);
pfn = pte_prefetch_gfn_to_pfn(vcpu, gfn,
- (pte_access & ACC_WRITE_MASK) && dirty);
+ pte_access & ACC_WRITE_MASK);
if (is_error_pfn(pfn)) {
kvm_release_pfn_clean(pfn);
break;
}

mmu_set_spte(vcpu, spte, sp->role.access, pte_access, 0, 0,
- dirty, NULL, PT_PAGE_TABLE_LEVEL, gfn,
+ NULL, PT_PAGE_TABLE_LEVEL, gfn,
pfn, true, true);
}
}
@@ -469,7 +470,6 @@ static u64 *FNAME(fetch)(struct kvm_vcpu *vcpu, gva_t addr,
{
unsigned access = gw->pt_access;
struct kvm_mmu_page *sp = NULL;
- bool dirty = is_dirty_gpte(gw->ptes[gw->level - 1]);
int top_level;
unsigned direct_access;
struct kvm_shadow_walk_iterator it;
@@ -478,8 +478,6 @@ static u64 *FNAME(fetch)(struct kvm_vcpu *vcpu, gva_t addr,
return NULL;

direct_access = gw->pt_access & gw->pte_access;
- if (!dirty)
- direct_access &= ~ACC_WRITE_MASK;

top_level = vcpu->arch.mmu.root_level;
if (top_level == PT32E_ROOT_LEVEL)
@@ -538,7 +536,7 @@ static u64 *FNAME(fetch)(struct kvm_vcpu *vcpu, gva_t addr,
}

mmu_set_spte(vcpu, it.sptep, access, gw->pte_access & access,
- user_fault, write_fault, dirty, ptwrite, it.level,
+ user_fault, write_fault, ptwrite, it.level,
gw->gfn, pfn, prefault, map_writable);
FNAME(pte_prefetch)(vcpu, gw, it.sptep);

@@ -621,17 +619,9 @@ static int FNAME(page_fault)(struct kvm_vcpu *vcpu, gva_t addr, u32 error_code,
return 0;

/* mmio */
- if (is_error_pfn(pfn)) {
- unsigned access = walker.pte_access;
- bool dirty = is_dirty_gpte(walker.ptes[walker.level - 1]);
-
- if (dirty)
- access &= ~ACC_WRITE_MASK;
-
+ if (is_error_pfn(pfn))
return kvm_handle_bad_page(vcpu, mmu_is_nested(vcpu) ? 0 :
- addr, access, walker.gfn, pfn);
- }
-
+ addr, walker.pte_access, walker.gfn, pfn);
spin_lock(&vcpu->kvm->mmu_lock);
if (mmu_notifier_retry(vcpu, mmu_seq))
goto out_unlock;
@@ -852,7 +842,7 @@ static int FNAME(sync_page)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp)
host_writable = sp->spt[i] & SPTE_HOST_WRITEABLE;

set_spte(vcpu, &sp->spt[i], pte_access, 0, 0,
- is_dirty_gpte(gpte), PT_PAGE_TABLE_LEVEL, gfn,
+ PT_PAGE_TABLE_LEVEL, gfn,
spte_to_pfn(sp->spt[i]), true, false,
host_writable);
}
--
1.7.4.4


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