diff mbox series

[4.14,038/237] KVM: nVMX: Use correct root level for nested EPT shadow page tables - again

Message ID 20200227132259.536427431@linuxfoundation.org
State Superseded
Headers show
Series None | expand

Commit Message

Greg Kroah-Hartman Feb. 27, 2020, 1:34 p.m. UTC 
From: Sean Christopherson <sean.j.christopherson@intel.com>

[ Upstream commit 148d735eb55d32848c3379e460ce365f2c1cbe4b ]

Hardcode the EPT page-walk level for L2 to be 4 levels, as KVM's MMU
currently also hardcodes the page walk level for nested EPT to be 4
levels.  The L2 guest is all but guaranteed to soft hang on its first
instruction when L1 is using EPT, as KVM will construct 4-level page
tables and then tell hardware to use 5-level page tables.

Fixes: 855feb673640 ("KVM: MMU: Add 5 level EPT & Shadow page table support.")
Cc: stable@vger.kernel.org
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 arch/x86/kvm/vmx.c | 3 +++
 1 file changed, 3 insertions(+)
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Patch

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 809d1b031fd9e..a116548a4ade1 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -4597,6 +4597,9 @@  static void vmx_set_cr0(struct kvm_vcpu *vcpu, unsigned long cr0)
 
 static int get_ept_level(struct kvm_vcpu *vcpu)
 {
+	/* Nested EPT currently only supports 4-level walks. */
+	if (is_guest_mode(vcpu) && nested_cpu_has_ept(get_vmcs12(vcpu)))
+		return 4;
 	if (cpu_has_vmx_ept_5levels() && (cpuid_maxphyaddr(vcpu) > 48))
 		return 5;
 	return 4;