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KVM: MMU: Simplify walk_addr_generic() loop 

The page table walk is coded as an infinite loop, with a special
case on the last pte.

Code it as an ordinary loop with a termination condition on the last
pte (large page or walk length exhausted), and put the last pte handling
code after the loop where it belongs.

Reviewed-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
hifive-unleashed-5.1
Avi Kivity 2012-09-12 15:12:09 +03:00
parent 97d64b7881
commit 13d22b6aeb
1 changed files with 25 additions and 35 deletions
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60
arch/x86/kvm/paging_tmpl.h
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@ -171,12 +171,15 @@ static int FNAME(walk_addr_generic)(struct guest_walker *walker,
gfn_t table_gfn;
unsigned index, pt_access, pte_access;
gpa_t pte_gpa;
bool eperm, last_gpte;
bool eperm;
int offset;
const int write_fault = access & PFERR_WRITE_MASK;
const int user_fault = access & PFERR_USER_MASK;
const int fetch_fault = access & PFERR_FETCH_MASK;
u16 errcode = 0;
gpa_t real_gpa;
gfn_t gfn;
u32 ac;
trace_kvm_mmu_pagetable_walk(addr, access);
retry_walk:
@ -197,12 +200,16 @@ retry_walk:
ASSERT((!is_long_mode(vcpu) && is_pae(vcpu)) ||
(mmu->get_cr3(vcpu) & CR3_NONPAE_RESERVED_BITS) == 0);
pt_access = ACC_ALL;
pt_access = pte_access = ACC_ALL;
++walker->level;
for (;;) {
do {
gfn_t real_gfn;
unsigned long host_addr;
pt_access &= pte_access;
--walker->level;
index = PT_INDEX(addr, walker->level);
table_gfn = gpte_to_gfn(pte);
@ -239,39 +246,8 @@ retry_walk:
pte_access = pt_access & gpte_access(vcpu, pte);
last_gpte = FNAME(is_last_gpte)(walker, vcpu, mmu, pte);
walker->ptes[walker->level - 1] = pte;
if (last_gpte) {
int lvl = walker->level;
gpa_t real_gpa;
gfn_t gfn;
u32 ac;
gfn = gpte_to_gfn_lvl(pte, lvl);
gfn += (addr & PT_LVL_OFFSET_MASK(lvl)) >> PAGE_SHIFT;
if (PTTYPE == 32 &&
walker->level == PT_DIRECTORY_LEVEL &&
is_cpuid_PSE36())
gfn += pse36_gfn_delta(pte);
ac = write_fault | fetch_fault | user_fault;
real_gpa = mmu->translate_gpa(vcpu, gfn_to_gpa(gfn),
ac);
if (real_gpa == UNMAPPED_GVA)
return 0;
walker->gfn = real_gpa >> PAGE_SHIFT;
break;
}
pt_access &= pte_access;
--walker->level;
}
} while (!FNAME(is_last_gpte)(walker, vcpu, mmu, pte));
eperm |= permission_fault(mmu, pte_access, access);
if (unlikely(eperm)) {
@ -279,6 +255,20 @@ retry_walk:
goto error;
}
gfn = gpte_to_gfn_lvl(pte, walker->level);
gfn += (addr & PT_LVL_OFFSET_MASK(walker->level)) >> PAGE_SHIFT;
if (PTTYPE == 32 && walker->level == PT_DIRECTORY_LEVEL && is_cpuid_PSE36())
gfn += pse36_gfn_delta(pte);
ac = write_fault | fetch_fault | user_fault;
real_gpa = mmu->translate_gpa(vcpu, gfn_to_gpa(gfn), ac);
if (real_gpa == UNMAPPED_GVA)
return 0;
walker->gfn = real_gpa >> PAGE_SHIFT;
if (!write_fault)
protect_clean_gpte(&pte_access, pte);