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KVM: nVMX: introduce nested_vmx_load_cr3 and call it on vmentry

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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: Ladi Prosek <lprosek@redhat.com>
Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
This commit is contained in:
Ladi Prosek 2016-11-30 16:03:10 +01:00 committed by Paolo Bonzini
parent ee146c1c10
commit 9ed38ffad4
3 changed files with 45 additions and 16 deletions
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1
arch/x86/include/asm/kvm_host.h
View File

@ -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);

57
arch/x86/kvm/vmx.c
View File

@ -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;
return 1;
}
}
/* 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);

3
arch/x86/kvm/x86.c
View File

@ -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)
{