On Thu, 2022-05-12 at 10:19 +0800, Zhiquan Li wrote: > On 2022/5/12 07:33, Kai Huang wrote: > > > + ret = force_sig_mceerr(BUS_MCEERR_AR, (void __user *)owner->vaddr, > > > + PAGE_SHIFT); > > If I understand correctly, this sends signal to the userspace hypervisor, i.e. > > Qemu? Can you elaborate how is KVM supposed to inject the #MC to guest, instead > > of Qemu process (the VM) being killed? > > > > Yes, here we use the facility that Qemu already has. > The basic call path as below: > > sigbus_handler > kvm_on_sigbus > kvm_arch_on_sigbus_vcpu > qemu_ram_addr_from_host > kvm_physical_memory_addr_from_host > kvm_hwpoison_page_add > kvm_mce_inject > cpu_x86_inject_mce > > 1. At first when Qemu init, it will register sigbus_handler() as its SIGBUS handler > at qemu_init_sigbus(). > 2. At sigbus_handler() it will filter-out the signal which siginfo->si_code is not > BUS_MCEERR_AO or BUS_MCEERR_AR, and then re-raise SIGBUS signal. > If the si_code is BUS_MCEERR_AO or BUS_MCEERR_AR, it will invoke > kvm_on_sigbus(siginfo->si_code, siginfo->si_addr), go on handling the signal. > 3. kvm_on_sigbus() is a simple generic wrap which will call arch specific > kvm_arch_on_sigbus_vcpu() > 4. kvm_arch_on_sigbus_vcpu() is x86 specific implementation, it will do following > 1) Convert HVA (addr) to HPA (ram_addr) > ram_addr = qemu_ram_addr_from_host(addr) > 2) Retrieve the GPA (paddr) as per HVA (addr) > kvm_physical_memory_addr_from_host(c->kvm_state, addr, &paddr) > 3) Add the page including HWPoison HPA to its hwpoison_page_list > kvm_hwpoison_page_add(ram_addr) > 4) Inject the #MC to guest with GPA and si_code > kvm_mce_inject(cpu, paddr, code) > cpu_x86_inject_mce() > > The rest is guest kernel uses the existed MCA to handle the #MC. According to the > physical address (in fact, GPA) find the applications and send kill signal if the > #MC is SRAR. > > So the intention of this patchset is to enrich the information when sending > SIGBUS, so that VMM can use already existed facility to take a proper behavior. > > Yes this makes sense. Thanks for explaining! -- Thanks, -Kai
