On 05/12/2017 07:21, Wanpeng Li wrote: > From: Wanpeng Li <[email protected]> > > The below test case can cause infinite loop in kvm when ept=0. > > #include <unistd.h> > #include <sys/syscall.h> > #include <string.h> > #include <stdint.h> > #include <linux/kvm.h> > #include <fcntl.h> > #include <sys/ioctl.h> > > long r[5]; > int main() > { > r[2] = open("/dev/kvm", O_RDONLY); > r[3] = ioctl(r[2], KVM_CREATE_VM, 0); > r[4] = ioctl(r[3], KVM_CREATE_VCPU, 7); > ioctl(r[4], KVM_RUN, 0); > } > > It doesn't setup the memory regions, mmu_alloc_shadow/direct_roots() in > kvm return 1 when kvm fails to allocate root page table which can result > in beblow infinite loop: > > vcpu_run() { > for (;;) { > r = vcpu_enter_guest()::kvm_mmu_reload() returns 1 > if (r <= 0) > break; > if (need_resched()) > cond_resched(); > } > } > > This patch fixes it by returning -ENOSPC when there is no available kvm mmu > page for root page table. > > Cc: Paolo Bonzini <[email protected]> > Cc: Radim Krčmář <[email protected]> > Fixes: 26eeb53cf0f (KVM: MMU: Bail out immediately if there is no available > mmu page) > Signed-off-by: Wanpeng Li <[email protected]> > --- > arch/x86/kvm/mmu.c | 8 ++++---- > 1 file changed, 4 insertions(+), 4 deletions(-) > > diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c > index c9aaa18..89da688 100644 > --- a/arch/x86/kvm/mmu.c > +++ b/arch/x86/kvm/mmu.c > @@ -3395,7 +3395,7 @@ static int mmu_alloc_direct_roots(struct kvm_vcpu *vcpu) > spin_lock(&vcpu->kvm->mmu_lock); > if(make_mmu_pages_available(vcpu) < 0) { > spin_unlock(&vcpu->kvm->mmu_lock); > - return 1; > + return -ENOSPC; > } > sp = kvm_mmu_get_page(vcpu, 0, 0, > vcpu->arch.mmu.shadow_root_level, 1, ACC_ALL); > @@ -3410,7 +3410,7 @@ static int mmu_alloc_direct_roots(struct kvm_vcpu *vcpu) > spin_lock(&vcpu->kvm->mmu_lock); > if (make_mmu_pages_available(vcpu) < 0) { > spin_unlock(&vcpu->kvm->mmu_lock); > - return 1; > + return -ENOSPC; > } > sp = kvm_mmu_get_page(vcpu, i << (30 - PAGE_SHIFT), > i << 30, PT32_ROOT_LEVEL, 1, ACC_ALL); > @@ -3450,7 +3450,7 @@ static int mmu_alloc_shadow_roots(struct kvm_vcpu *vcpu) > spin_lock(&vcpu->kvm->mmu_lock); > if (make_mmu_pages_available(vcpu) < 0) { > spin_unlock(&vcpu->kvm->mmu_lock); > - return 1; > + return -ENOSPC; > } > sp = kvm_mmu_get_page(vcpu, root_gfn, 0, > vcpu->arch.mmu.shadow_root_level, 0, ACC_ALL); > @@ -3487,7 +3487,7 @@ static int mmu_alloc_shadow_roots(struct kvm_vcpu *vcpu) > spin_lock(&vcpu->kvm->mmu_lock); > if (make_mmu_pages_available(vcpu) < 0) { > spin_unlock(&vcpu->kvm->mmu_lock); > - return 1; > + return -ENOSPC; > } > sp = kvm_mmu_get_page(vcpu, root_gfn, i << 30, PT32_ROOT_LEVEL, > 0, ACC_ALL); >
Queued, thanks.
