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Commit 13d22b6a authored by Avi Kivity's avatar Avi Kivity
Browse files

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: default avatarXiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Signed-off-by: default avatarAvi Kivity <avi@redhat.com>
parent 97d64b78

arch/x86/kvm/paging_tmpl.h

+25 −35
Original line number Diff line number Diff line
@@ -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 @@ static int FNAME(walk_addr_generic)(struct guest_walker *walker, 
	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);
@@ -239,46 +246,29 @@ static int FNAME(walk_addr_generic)(struct guest_walker *walker, 


		pte_access = pt_access & gpte_access(vcpu, pte);



		last_gpte = FNAME(is_last_gpte)(walker, vcpu, mmu, pte);



		walker->ptes[walker->level - 1] = pte;

	} while (!FNAME(is_last_gpte)(walker, vcpu, mmu, pte));



		if (last_gpte) {

			int lvl = walker->level;

			gpa_t real_gpa;

			gfn_t gfn;

			u32 ac;

	eperm |= permission_fault(mmu, pte_access, access);

	if (unlikely(eperm)) {

		errcode |= PFERR_PRESENT_MASK;

		goto error;

	}



			gfn = gpte_to_gfn_lvl(pte, lvl);

			gfn += (addr & PT_LVL_OFFSET_MASK(lvl)) >> PAGE_SHIFT;

	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())

	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);

	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;

	}



	eperm |= permission_fault(mmu, pte_access, access);

	if (unlikely(eperm)) {

		errcode |= PFERR_PRESENT_MASK;

		goto error;

	}



	if (!write_fault)

		protect_clean_gpte(&pte_access, pte);