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ebd1a33655
Handle Machine Checks (#MC) that happen in the guest (by forwarding them to the host) outside of KVM's fastpath so that as much host state as possible is re-loaded before invoking the kernel's #MC handler. The only requirement is that KVM invokes the #MC handler before enabling IRQs (and even that could _probably_ be relaxed to handling #MCs before enabling preemption). Waiting to handle #MCs until "more" host state is loaded hardens KVM against flaws in the #MC handler, which has historically been quite brittle. E.g. prior to commit5567d11c21("x86/mce: Send #MC singal from task work"), the #MC code could trigger a schedule() with IRQs and preemption disabled. That led to a KVM hack-a-fix in commit1811d979c7("x86/kvm: move kvm_load/put_guest_xcr0 into atomic context"). Note, except for #MCs on VM-Enter, VMX already handles #MCs outside of the fastpath. Reviewed-by: Rick Edgecombe <rick.p.edgecombe@intel.com> Reviewed-by: Jon Kohler <jon@nutanix.com> Link: https://patch.msgid.link/20251118222328.2265758-2-seanjc@google.com Signed-off-by: Sean Christopherson <seanjc@google.com>