Re: [PATCH v3 08/12] KVM: Propagate vcpu explicitly to mark_page_dirty_in_slot()
From: Sean Christopherson <seanjc@google.com>
Date: 2021-11-18 18:42:38
Also in:
kvm, kvm-riscv, kvmarm, linux-arm-kernel, linux-mips, linux-s390
On Thu, Nov 18, 2021, David Woodhouse wrote:
That leaves the one in TDP MMU handle_changed_spte_dirty_log() which AFAICT can trigger the same crash seen by butt3rflyh4ck — can't that happen from a thread where kvm_get_running_vcpu() is NULL too? For that one I'm not sure.
I think could be trigger in the TDP MMU via kvm_mmu_notifier_release() -> kvm_mmu_zap_all(), e.g. if the userspace VMM exits while dirty logging is enabled. That should be easy to (dis)prove via a selftest. And for the record :-) On Mon, Dec 02, 2019 at 12:10:36PM -0800, Sean Christopherson wrote:
IMO, adding kvm_get_running_vcpu() is a hack that is just asking for future abuse and the vcpu/vm/as_id interactions in mark_page_dirty_in_ring() look extremely fragile.
On 03/12/19 20:01, Sean Christopherson wrote:
In case it was clear, I strongly dislike adding kvm_get_running_vcpu(). IMO, it's a unnecessary hack. The proper change to ensure a valid vCPU is seen by mark_page_dirty_in_ring() when there is a current vCPU is to plumb the vCPU down through the various call stacks.