diff options
author | Peter Shier <pshier@google.com> | 2020-08-21 02:05:45 +0300 |
---|---|---|
committer | Paolo Bonzini <pbonzini@redhat.com> | 2020-09-11 20:15:09 +0300 |
commit | 43fea4e42599c3eb4109996698f5c25761d3f815 (patch) | |
tree | a96050499c41cab0e291ed2ad2d26b184161ff90 /arch/x86 | |
parent | 1b67fd086dd7be076f190dfe4b52403d0cf58375 (diff) | |
download | linux-43fea4e42599c3eb4109996698f5c25761d3f815.tar.xz |
KVM: nVMX: Update VMCS02 when L2 PAE PDPTE updates detected
When L2 uses PAE, L0 intercepts of L2 writes to CR0/CR3/CR4 call
load_pdptrs to read the possibly updated PDPTEs from the guest
physical address referenced by CR3. It loads them into
vcpu->arch.walk_mmu->pdptrs and sets VCPU_EXREG_PDPTR in
vcpu->arch.regs_dirty.
At the subsequent assumed reentry into L2, the mmu will call
vmx_load_mmu_pgd which calls ept_load_pdptrs. ept_load_pdptrs sees
VCPU_EXREG_PDPTR set in vcpu->arch.regs_dirty and loads
VMCS02.GUEST_PDPTRn from vcpu->arch.walk_mmu->pdptrs[]. This all works
if the L2 CRn write intercept always resumes L2.
The resume path calls vmx_check_nested_events which checks for
exceptions, MTF, and expired VMX preemption timers. If
vmx_check_nested_events finds any of these conditions pending it will
reflect the corresponding exit into L1. Live migration at this point
would also cause a missed immediate reentry into L2.
After L1 exits, vmx_vcpu_run calls vmx_register_cache_reset which
clears VCPU_EXREG_PDPTR in vcpu->arch.regs_dirty. When L2 next
resumes, ept_load_pdptrs finds VCPU_EXREG_PDPTR clear in
vcpu->arch.regs_dirty and does not load VMCS02.GUEST_PDPTRn from
vcpu->arch.walk_mmu->pdptrs[]. prepare_vmcs02 will then load
VMCS02.GUEST_PDPTRn from vmcs12->pdptr0/1/2/3 which contain the stale
values stored at last L2 exit. A repro of this bug showed L2 entering
triple fault immediately due to the bad VMCS02.GUEST_PDPTRn values.
When L2 is in PAE paging mode add a call to ept_load_pdptrs before
leaving L2. This will update VMCS02.GUEST_PDPTRn if they are dirty in
vcpu->arch.walk_mmu->pdptrs[].
Tested:
kvm-unit-tests with new directed test: vmx_mtf_pdpte_test.
Verified that test fails without the fix.
Also ran Google internal VMM with an Ubuntu 16.04 4.4.0-83 guest running a
custom hypervisor with a 32-bit Windows XP L2 guest using PAE. Prior to fix
would repro readily. Ran 14 simultaneous L2s for 140 iterations with no
failures.
Signed-off-by: Peter Shier <pshier@google.com>
Reviewed-by: Jim Mattson <jmattson@google.com>
Message-Id: <20200820230545.2411347-1-pshier@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'arch/x86')
-rw-r--r-- | arch/x86/kvm/vmx/nested.c | 8 | ||||
-rw-r--r-- | arch/x86/kvm/vmx/vmx.c | 4 | ||||
-rw-r--r-- | arch/x86/kvm/vmx/vmx.h | 1 |
3 files changed, 11 insertions, 2 deletions
diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c index 23b58c28a1c9..d7482ccf6a8d 100644 --- a/arch/x86/kvm/vmx/nested.c +++ b/arch/x86/kvm/vmx/nested.c @@ -4404,6 +4404,14 @@ void nested_vmx_vmexit(struct kvm_vcpu *vcpu, u32 vm_exit_reason, if (kvm_check_request(KVM_REQ_TLB_FLUSH_CURRENT, vcpu)) kvm_vcpu_flush_tlb_current(vcpu); + /* + * VCPU_EXREG_PDPTR will be clobbered in arch/x86/kvm/vmx/vmx.h between + * now and the new vmentry. Ensure that the VMCS02 PDPTR fields are + * up-to-date before switching to L1. + */ + if (enable_ept && is_pae_paging(vcpu)) + vmx_ept_load_pdptrs(vcpu); + leave_guest_mode(vcpu); if (nested_cpu_has_preemption_timer(vmcs12)) diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c index 46ba2e03a892..19a599bebd5c 100644 --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -2971,7 +2971,7 @@ static void vmx_flush_tlb_guest(struct kvm_vcpu *vcpu) vpid_sync_context(to_vmx(vcpu)->vpid); } -static void ept_load_pdptrs(struct kvm_vcpu *vcpu) +void vmx_ept_load_pdptrs(struct kvm_vcpu *vcpu) { struct kvm_mmu *mmu = vcpu->arch.walk_mmu; @@ -3114,7 +3114,7 @@ static void vmx_load_mmu_pgd(struct kvm_vcpu *vcpu, unsigned long pgd, guest_cr3 = vcpu->arch.cr3; else /* vmcs01.GUEST_CR3 is already up-to-date. */ update_guest_cr3 = false; - ept_load_pdptrs(vcpu); + vmx_ept_load_pdptrs(vcpu); } else { guest_cr3 = pgd; } diff --git a/arch/x86/kvm/vmx/vmx.h b/arch/x86/kvm/vmx/vmx.h index 26175a4759fa..a2f82127c170 100644 --- a/arch/x86/kvm/vmx/vmx.h +++ b/arch/x86/kvm/vmx/vmx.h @@ -356,6 +356,7 @@ void vmx_update_host_rsp(struct vcpu_vmx *vmx, unsigned long host_rsp); int vmx_find_msr_index(struct vmx_msrs *m, u32 msr); int vmx_handle_memory_failure(struct kvm_vcpu *vcpu, int r, struct x86_exception *e); +void vmx_ept_load_pdptrs(struct kvm_vcpu *vcpu); #define POSTED_INTR_ON 0 #define POSTED_INTR_SN 1 |