Commit 9ed38ffa authored by Ladi Prosek's avatar Ladi Prosek Committed by Paolo Bonzini
Browse files

KVM: nVMX: introduce nested_vmx_load_cr3 and call it on vmentry 



Loading CR3 as part of emulating vmentry is different from regular CR3 loads,
as implemented in kvm_set_cr3, in several ways.

* different rules are followed to check CR3 and it is desirable for the caller
to distinguish between the possible failures
* PDPTRs are not loaded if PAE paging and nested EPT are both enabled
* many MMU operations are not necessary

This patch introduces nested_vmx_load_cr3 suitable for CR3 loads as part of
nested vmentry and vmexit, and makes use of it on the nested vmentry path.

Signed-off-by: default avatarLadi Prosek <lprosek@redhat.com>
Signed-off-by: default avatarRadim Krčmář <rkrcmar@redhat.com>
parent ee146c1c

arch/x86/include/asm/kvm_host.h

+1 −0
Original line number Diff line number Diff line
@@ -1071,6 +1071,7 @@ unsigned int kvm_mmu_calculate_mmu_pages(struct kvm *kvm); 
void kvm_mmu_change_mmu_pages(struct kvm *kvm, unsigned int kvm_nr_mmu_pages);



int load_pdptrs(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu, unsigned long cr3);

bool pdptrs_changed(struct kvm_vcpu *vcpu);



int emulator_write_phys(struct kvm_vcpu *vcpu, gpa_t gpa,

			  const void *val, int bytes);

arch/x86/kvm/vmx.c

+42 −15
Original line number Diff line number Diff line
@@ -9968,6 +9968,44 @@ static int nested_vmx_store_msr(struct kvm_vcpu *vcpu, u64 gpa, u32 count) 
	return 0;

}



/*

 * Load guest's/host's cr3 at nested entry/exit. nested_ept is true if we are

 * emulating VM entry into a guest with EPT enabled.

 * Returns 0 on success, 1 on failure. Invalid state exit qualification code

 * is assigned to entry_failure_code on failure.

 */

static int nested_vmx_load_cr3(struct kvm_vcpu *vcpu, unsigned long cr3, bool nested_ept,

			       unsigned long *entry_failure_code)

{

	unsigned long invalid_mask;



	if (cr3 != kvm_read_cr3(vcpu) || (!nested_ept && pdptrs_changed(vcpu))) {

		invalid_mask = (~0ULL) << cpuid_maxphyaddr(vcpu);

		if (cr3 & invalid_mask) {

			*entry_failure_code = ENTRY_FAIL_DEFAULT;

			return 1;

		}



		/*

		 * If PAE paging and EPT are both on, CR3 is not used by the CPU and

		 * must not be dereferenced.

		 */

		if (!is_long_mode(vcpu) && is_pae(vcpu) && is_paging(vcpu) &&

		    !nested_ept) {

			if (!load_pdptrs(vcpu, vcpu->arch.walk_mmu, cr3)) {

				*entry_failure_code = ENTRY_FAIL_PDPTE;

				return 1;

			}

		}



		vcpu->arch.cr3 = cr3;

		__set_bit(VCPU_EXREG_CR3, (ulong *)&vcpu->arch.regs_avail);

	}



	kvm_mmu_reset_context(vcpu);

	return 0;

}



/*

 * prepare_vmcs02 is called when the L1 guest hypervisor runs its nested

 * L2 guest. L1 has a vmcs for L2 (vmcs12), and this function "merges" it
@@ -10300,21 +10338,10 @@ static int prepare_vmcs02(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12, 
	/* Note: modifies VM_ENTRY/EXIT_CONTROLS and GUEST/HOST_IA32_EFER */

	vmx_set_efer(vcpu, vcpu->arch.efer);



	/*

	 * Shadow page tables on either EPT or shadow page tables.

	 * If PAE and EPT are both on, CR3 is not used by the CPU and must not

	 * be dereferenced.

	 */

	if (is_pae(vcpu) && is_paging(vcpu) && !is_long_mode(vcpu) &&

	    nested_ept_enabled) {

		vcpu->arch.cr3 = vmcs12->guest_cr3;

		__set_bit(VCPU_EXREG_CR3, (ulong *)&vcpu->arch.regs_avail);

	} else {

		if (kvm_set_cr3(vcpu, vmcs12->guest_cr3)) {

			*entry_failure_code = ENTRY_FAIL_DEFAULT;

	/* Shadow page tables on either EPT or shadow page tables. */

	if (nested_vmx_load_cr3(vcpu, vmcs12->guest_cr3, nested_ept_enabled,

				entry_failure_code))

		return 1;

		}

	}



	kvm_mmu_reset_context(vcpu);

arch/x86/kvm/x86.c

+2 −1
Original line number Diff line number Diff line
@@ -566,7 +566,7 @@ out: 
}

EXPORT_SYMBOL_GPL(load_pdptrs);



static bool pdptrs_changed(struct kvm_vcpu *vcpu)

bool pdptrs_changed(struct kvm_vcpu *vcpu)

{

	u64 pdpte[ARRAY_SIZE(vcpu->arch.walk_mmu->pdptrs)];

	bool changed = true;
@@ -592,6 +592,7 @@ out: 


	return changed;

}

EXPORT_SYMBOL_GPL(pdptrs_changed);



int kvm_set_cr0(struct kvm_vcpu *vcpu, unsigned long cr0)

{

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