Messages in this thread | | | From | "Maciej S. Szmigiero" <> | Subject | Re: [PATCH v5 04/13] KVM: x86: Move n_memslots_pages recalc to kvm_arch_prepare_memory_region() | Date | Wed, 20 Oct 2021 20:41:13 +0200 |
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On 20.10.2021 00:38, Sean Christopherson wrote: > On Mon, Sep 20, 2021, Maciej S. Szmigiero wrote: >> From: "Maciej S. Szmigiero" <maciej.szmigiero@oracle.com> >> >> This allows us to return a proper error code in case we spot an underflow. >> >> Signed-off-by: Maciej S. Szmigiero <maciej.szmigiero@oracle.com> >> --- >> arch/x86/kvm/x86.c | 49 ++++++++++++++++++++++++++-------------------- >> 1 file changed, 28 insertions(+), 21 deletions(-) >> >> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c >> index 97d86223427d..0fffb8414009 100644 >> --- a/arch/x86/kvm/x86.c >> +++ b/arch/x86/kvm/x86.c >> @@ -11511,9 +11511,23 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm, >> const struct kvm_userspace_memory_region *mem, >> enum kvm_mr_change change) >> { >> - if (change == KVM_MR_CREATE || change == KVM_MR_MOVE) >> - return kvm_alloc_memslot_metadata(kvm, new, >> - mem->memory_size >> PAGE_SHIFT); >> + if (change == KVM_MR_CREATE || change == KVM_MR_MOVE) { >> + int ret; >> + >> + ret = kvm_alloc_memslot_metadata(kvm, new, >> + mem->memory_size >> PAGE_SHIFT); >> + if (ret) >> + return ret; >> + >> + if (change == KVM_MR_CREATE) >> + kvm->arch.n_memslots_pages += new->npages; >> + } else if (change == KVM_MR_DELETE) { >> + if (WARN_ON(kvm->arch.n_memslots_pages < old->npages)) >> + return -EIO; > > This is not worth the churn. In a way, it's worse because userspace can spam > the living snot out of the kernel log by retrying the ioctl(). > > Since underflow can happen if and only if there's a KVM bug, and a pretty bad one > at that, just make the original WARN_ON a KVM_BUG_ON. That will kill the VM and > also provide the WARN_ON_ONCE behavior that we probably want.
Will do.
Thanks, Maciej
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