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KVM: MMU: Simplify spte fetch() function

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Partition the function into three sections:

- fetching indirect shadow pages (host_level > guest_level)
- fetching direct shadow pages (page_level < host_level <= guest_level)
- the final spte (page_level == host_level)

Instead of the current spaghetti.

A slight change from the original code is that we call validate_direct_spte()
more often: previously we called it only for gw->level, now we also call it for
lower levels.  The change should have no effect.

[xiao: fix regression caused by validate_direct_spte() called too late]

Signed-off-by: Avi Kivity <avi@redhat.com>
Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
This commit is contained in:
Avi Kivity 2010-07-13 14:27:09 +03:00
parent 39c8c672a1
commit 0b3c933302
1 changed files with 49 additions and 44 deletions
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93
arch/x86/kvm/paging_tmpl.h
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@ -321,9 +321,7 @@ static u64 *FNAME(fetch)(struct kvm_vcpu *vcpu, gva_t addr,
unsigned access = gw->pt_access;
struct kvm_mmu_page *sp;
u64 *sptep = NULL;
int direct;
gfn_t table_gfn;
int level;
int uninitialized_var(level);
bool dirty = is_dirty_gpte(gw->ptes[gw->level - 1]);
unsigned direct_access;
struct kvm_shadow_walk_iterator iterator;
@ -335,61 +333,68 @@ static u64 *FNAME(fetch)(struct kvm_vcpu *vcpu, gva_t addr,
if (!dirty)
direct_access &= ~ACC_WRITE_MASK;
for_each_shadow_entry(vcpu, addr, iterator) {
for (shadow_walk_init(&iterator, vcpu, addr);
shadow_walk_okay(&iterator) && iterator.level > gw->level;
shadow_walk_next(&iterator)) {
gfn_t table_gfn;
level = iterator.level;
sptep = iterator.sptep;
if (iterator.level == hlevel) {
mmu_set_spte(vcpu, sptep, access,
gw->pte_access & access,
user_fault, write_fault,
dirty, ptwrite, level,
gw->gfn, pfn, false, true);
break;
}
if (is_shadow_present_pte(*sptep) && !is_large_pte(*sptep)
&& level == gw->level)
validate_direct_spte(vcpu, sptep, direct_access);
drop_large_spte(vcpu, sptep);
if (is_shadow_present_pte(*sptep))
continue;
if (level <= gw->level) {
direct = 1;
access = direct_access;
/*
* It is a large guest pages backed by small host pages,
* So we set @direct(@sp->role.direct)=1, and set
* @table_gfn(@sp->gfn)=the base page frame for linear
* translations.
*/
table_gfn = gw->gfn & ~(KVM_PAGES_PER_HPAGE(level) - 1);
access &= gw->pte_access;
} else {
direct = 0;
table_gfn = gw->table_gfn[level - 2];
}
table_gfn = gw->table_gfn[level - 2];
sp = kvm_mmu_get_page(vcpu, table_gfn, addr, level-1,
direct, access, sptep);
if (!direct)
/*
* Verify that the gpte in the page we've just write
* protected is still there.
*/
if (FNAME(gpte_changed)(vcpu, gw, level - 1)) {
kvm_mmu_put_page(sp, sptep);
kvm_release_pfn_clean(pfn);
sptep = NULL;
break;
}
false, access, sptep);
/*
* Verify that the gpte in the page we've just write
* protected is still there.
*/
if (FNAME(gpte_changed)(vcpu, gw, level - 1))
goto out_gpte_changed;
link_shadow_page(sptep, sp);
}
for (;
shadow_walk_okay(&iterator) && iterator.level > hlevel;
shadow_walk_next(&iterator)) {
gfn_t direct_gfn;
level = iterator.level;
sptep = iterator.sptep;
validate_direct_spte(vcpu, sptep, direct_access);
drop_large_spte(vcpu, sptep);
if (is_shadow_present_pte(*sptep))
continue;
direct_gfn = gw->gfn & ~(KVM_PAGES_PER_HPAGE(level) - 1);
sp = kvm_mmu_get_page(vcpu, direct_gfn, addr, level-1,
true, direct_access, sptep);
link_shadow_page(sptep, sp);
}
sptep = iterator.sptep;
level = iterator.level;
mmu_set_spte(vcpu, sptep, access, gw->pte_access & access,
user_fault, write_fault, dirty, ptwrite, level,
gw->gfn, pfn, false, true);
return sptep;
out_gpte_changed:
kvm_mmu_put_page(sp, sptep);
kvm_release_pfn_clean(pfn);
return NULL;
}
/*