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SubjectRe: [PATCH v5 3/3] KVM: nVMX: Fix mmu context after VMLAUNCH/VMRESUME failure
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On 11/02/2017 05:50 PM, Wanpeng Li wrote:

> From: Wanpeng Li <wanpeng.li@hotmail.com>
>
> Commit 4f350c6dbcb (kvm: nVMX: Handle deferred early VMLAUNCH/VMRESUME failure
> properly) can result in L1(run kvm-unit-tests/run_tests.sh vmx_controls in L1)
> null pointer deference and also L0 calltrace when EPT=0 on both L0 and L1.
>
> In L1:
>
> BUG: unable to handle kernel paging request at ffffffffc015bf8f
> IP: vmx_vcpu_run+0x202/0x510 [kvm_intel]
> PGD 146e13067 P4D 146e13067 PUD 146e15067 PMD 3d2686067 PTE 3d4af9161
> Oops: 0003 [#1] PREEMPT SMP
> CPU: 2 PID: 1798 Comm: qemu-system-x86 Not tainted 4.14.0-rc4+ #6
> RIP: 0010:vmx_vcpu_run+0x202/0x510 [kvm_intel]
> Call Trace:
> WARNING: kernel stack frame pointer at ffffb86f4988bc18 in qemu-system-x86:1798 has bad value 0000000000000002
>
> In L0:
>
> -----------[ cut here ]------------
> WARNING: CPU: 6 PID: 4460 at /home/kernel/linux/arch/x86/kvm//vmx.c:9845 vmx_inject_page_fault_nested+0x130/0x140 [kvm_intel]
> CPU: 6 PID: 4460 Comm: qemu-system-x86 Tainted: G OE 4.14.0-rc7+ #25
> RIP: 0010:vmx_inject_page_fault_nested+0x130/0x140 [kvm_intel]
> Call Trace:
> paging64_page_fault+0x500/0xde0 [kvm]
> ? paging32_gva_to_gpa_nested+0x120/0x120 [kvm]
> ? nonpaging_page_fault+0x3b0/0x3b0 [kvm]
> ? __asan_storeN+0x12/0x20
> ? paging64_gva_to_gpa+0xb0/0x120 [kvm]
> ? paging64_walk_addr_generic+0x11a0/0x11a0 [kvm]
> ? lock_acquire+0x2c0/0x2c0
> ? vmx_read_guest_seg_ar+0x97/0x100 [kvm_intel]
> ? vmx_get_segment+0x2a6/0x310 [kvm_intel]
> ? sched_clock+0x1f/0x30
> ? check_chain_key+0x137/0x1e0
> ? __lock_acquire+0x83c/0x2420
> ? kvm_multiple_exception+0xf2/0x220 [kvm]
> ? debug_check_no_locks_freed+0x240/0x240
> ? debug_smp_processor_id+0x17/0x20
> ? __lock_is_held+0x9e/0x100
> kvm_mmu_page_fault+0x90/0x180 [kvm]
> kvm_handle_page_fault+0x15c/0x310 [kvm]
> ? __lock_is_held+0x9e/0x100
> handle_exception+0x3c7/0x4d0 [kvm_intel]
> vmx_handle_exit+0x103/0x1010 [kvm_intel]
> ? kvm_arch_vcpu_ioctl_run+0x1628/0x2e20 [kvm]
>
> The commit avoids to load host state of vmcs12 as vmcs01's guest state
> since vmcs12 is not modified (except for the VM-instruction error field)
> if the checking of vmcs control area fails. However, the mmu context is
> switched to nested mmu in prepare_vmcs02() and it will not be reloaded
> since load_vmcs12_host_state() is skipped when nested VMLAUNCH/VMRESUME
> fails. This patch fixes it by reloading mmu context when nested
> VMLAUNCH/VMRESUME fails.
>
> Cc: Paolo Bonzini <pbonzini@redhat.com>
> Cc: Radim Krčmář <rkrcmar@redhat.com>
> Cc: Jim Mattson <jmattson@google.com>
> Signed-off-by: Wanpeng Li <wanpeng.li@hotmail.com>
> ---
> v3 -> v4:
> * move it to a new function load_vmcs12_mmu_host_state
>
> arch/x86/kvm/vmx.c | 34 ++++++++++++++++++++++------------
> 1 file changed, 22 insertions(+), 12 deletions(-)
>
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index 6cf3972..8aefb91 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -11259,6 +11259,24 @@ static void prepare_vmcs12(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12,
> kvm_clear_interrupt_queue(vcpu);
> }
>
> +static void load_vmcs12_mmu_host_state(struct kvm_vcpu *vcpu,
> + struct vmcs12 *vmcs12)
> +{
> + u32 entry_failure_code;
> +
> + nested_ept_uninit_mmu_context(vcpu);
> +
> + /*
> + * Only PDPTE load can fail as the value of cr3 was checked on entry and
> + * couldn't have changed.
> + */
> + if (nested_vmx_load_cr3(vcpu, vmcs12->host_cr3, false, &entry_failure_code))
> + nested_vmx_abort(vcpu, VMX_ABORT_LOAD_HOST_PDPTE_FAIL);
> +
> + if (!enable_ept)
> + vcpu->arch.walk_mmu->inject_page_fault = kvm_inject_page_fault;
> +}
> +
> /*
> * A part of what we need to when the nested L2 guest exits and we want to
> * run its L1 parent, is to reset L1's guest state to the host state specified
> @@ -11272,7 +11290,6 @@ static void load_vmcs12_host_state(struct kvm_vcpu *vcpu,
> struct vmcs12 *vmcs12)
> {
> struct kvm_segment seg;
> - u32 entry_failure_code;
>
> if (vmcs12->vm_exit_controls & VM_EXIT_LOAD_IA32_EFER)
> vcpu->arch.efer = vmcs12->host_ia32_efer;
> @@ -11299,17 +11316,7 @@ static void load_vmcs12_host_state(struct kvm_vcpu *vcpu,
> vcpu->arch.cr4_guest_owned_bits = ~vmcs_readl(CR4_GUEST_HOST_MASK);
> vmx_set_cr4(vcpu, vmcs12->host_cr4);
>
> - nested_ept_uninit_mmu_context(vcpu);
> -
> - /*
> - * Only PDPTE load can fail as the value of cr3 was checked on entry and
> - * couldn't have changed.
> - */
> - if (nested_vmx_load_cr3(vcpu, vmcs12->host_cr3, false, &entry_failure_code))
> - nested_vmx_abort(vcpu, VMX_ABORT_LOAD_HOST_PDPTE_FAIL);
> -
> - if (!enable_ept)
> - vcpu->arch.walk_mmu->inject_page_fault = kvm_inject_page_fault;
> + load_vmcs12_mmu_host_state(vcpu, vmcs12);
>
> if (enable_vpid) {
> /*
> @@ -11539,6 +11546,9 @@ static void nested_vmx_vmexit(struct kvm_vcpu *vcpu, u32 exit_reason,
> * accordingly.
> */
> nested_vmx_failValid(vcpu, VMXERR_ENTRY_INVALID_CONTROL_FIELD);
> +
> + load_vmcs12_mmu_host_state(vcpu, vmcs12);
> +
> /*
> * The emulated instruction was already skipped in
> * nested_vmx_run, but the updated RIP was never
Reviewed-by: Krish Sadhukhan <krish.sadhukhan@oracle.com>

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