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.
Best Regards,
Zhiquan
>
> -- Thanks, -Kai
