On 07/10/2012 01:05 AM, Avi Kivity wrote:
> Currently we check that the mmu root exits before every entry. Use the
> existing KVM_REQ_MMU_RELOAD mechanism instead, by making it really reload
> the mmu, and by adding the request to mmu initialization code.
>
> Signed-off-by: Avi Kivity <avi@xxxxxxxxxx>
> ---
> arch/x86/kvm/mmu.c | 4 +++-
> arch/x86/kvm/svm.c | 1 +
> arch/x86/kvm/x86.c | 13 +++++++------
> 3 files changed, 11 insertions(+), 7 deletions(-)
>
> diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
> index 569cd66..136d757 100644
> --- a/arch/x86/kvm/mmu.c
> +++ b/arch/x86/kvm/mmu.c
> @@ -3180,7 +3180,8 @@ void kvm_mmu_flush_tlb(struct kvm_vcpu *vcpu)
> static void paging_new_cr3(struct kvm_vcpu *vcpu)
> {
> pgprintk("%s: cr3 %lx\n", __func__, kvm_read_cr3(vcpu));
> - mmu_free_roots(vcpu);
> + kvm_mmu_unload(vcpu);
> + kvm_mmu_load(vcpu);
> }
>
> static unsigned long get_cr3(struct kvm_vcpu *vcpu)
> @@ -3469,6 +3470,7 @@ static int init_kvm_nested_mmu(struct kvm_vcpu *vcpu)
>
> static int init_kvm_mmu(struct kvm_vcpu *vcpu)
> {
> + kvm_make_request(KVM_REQ_MMU_RELOAD, vcpu);
> if (mmu_is_nested(vcpu))
> return init_kvm_nested_mmu(vcpu);
> else if (tdp_enabled)
> diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
> index 7a41878..d77ad8c 100644
> --- a/arch/x86/kvm/svm.c
> +++ b/arch/x86/kvm/svm.c
> @@ -2523,6 +2523,7 @@ static bool nested_svm_vmrun(struct vcpu_svm *svm)
>
> if (nested_vmcb->control.nested_ctl) {
> kvm_mmu_unload(&svm->vcpu);
> + kvm_make_request(KVM_REQ_MMU_RELOAD, &svm->vcpu);
> svm->nested.nested_cr3 = nested_vmcb->control.nested_cr3;
> nested_svm_init_mmu_context(&svm->vcpu);
> }
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 959e5a9..162231f 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -5226,8 +5226,14 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
> kvm_make_request(KVM_REQ_EVENT, vcpu);
>
> if (vcpu->requests) {
> - if (kvm_check_request(KVM_REQ_MMU_RELOAD, vcpu))
> + if (kvm_check_request(KVM_REQ_MMU_RELOAD, vcpu)) {
> kvm_mmu_unload(vcpu);
> + r = kvm_mmu_reload(vcpu);
> + if (unlikely(r)) {
> + kvm_make_request(KVM_REQ_MMU_RELOAD, vcpu);
> + goto out;
> + }
Now, reload mmu is before event injecting, can below bug be triggered again?
commit d8368af8b46b904def42a0f341d2f4f29001fa77
Author: Avi Kivity <avi@xxxxxxxxxx>
Date: Mon May 14 18:07:56 2012 +0300
KVM: Fix mmu_reload() clash with nested vmx event injection
Currently the inject_pending_event() call during guest entry happens after
kvm_mmu_reload(). This is for historical reasons - we used to
inject_pending_event() in atomic context, while kvm_mmu_reload() needs task
context.
A problem is that nested vmx can cause the mmu context to be reset, if event
injection is intercepted and causes a #VMEXIT instead (the #VMEXIT resets
CR0/CR3/CR4). If this happens, we end up with invalid root_hpa, and since
kvm_mmu_reload() has already run, no one will fix it and we end up entering
the guest this way.
Fix by reordering event injection to be before kvm_mmu_reload(). Use
->cancel_injection() to undo if kvm_mmu_reload() fails.
https://bugzilla.kernel.org/show_bug.cgi?id=42980
Reported-by: Luke-Jr <luke-jr+linuxbugs@xxxxxxxxxxx>
Signed-off-by: Avi Kivity <avi@xxxxxxxxxx>
Signed-off-by: Marcelo Tosatti <mtosatti@xxxxxxxxxx>
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