Hi guys, On 19/07/18 10:29, gengdongjiu wrote: > On 2018/7/19 17:10, Peter Maydell wrote: >>> The user space will firstly check the KVM_CAP_VCPU_EVENTS through kvm_has_vcpu_events() to know whether KVM can support get/set vcpu events, >>> If KVM supports get/set vcpu events, it will check KVM_CAP_ARM_SET_SERROR_ESR to know whether can set guest SError ESR, as shown the user space code in [1]. >> OK, so this capability affects the behaviour of >> KVM_SET_VCPU_EVENTS. Can you make sure the documentation >> of KVM_SET_VCPU_EVENTS clearly explains what happens >> and the effect of whether this capability is present, >> please? People trying to understand the behaviour of >> that ioctl are not going to know that they need to >> look here as well. > sure, I will. Thanks peter's reminder and comments. I've collected these changes, this description currently reads: ------------------%<------------------ This capability indicates that userspace can specify the syndrome value reported to the guest when it takes a virtual SError interrupt exception. If KVM advertises this capability, userspace can only specify the ISS field for the ESR syndrome. Other parts of the ESR, such as the EC are generated by the CPU when the exception is taken. If this virtual SError is taken to EL1 using AArch64, this value will be reported in the ISS field of ESR_ELx. See KVM_CAP_VCPU_EVENTS for more details. ------------------%<------------------ and this patch adds to the GET/SET API section with: ------------------%<------------------ SError exceptions always have an ESR value. Some CPUs have the ability to specify what the virtual SError's ESR value should be. These systems will advertise KVM_CAP_ARM_SET_SERROR_ESR. In this case exception.has_esr will always have a non-zero value when read, and the agent making an SError pending should specify the ISS field in the lower 24 bits of exception.serror_esr. If the system supports KVM_CAP_ARM_SET_SERROR_ESR, but user-space sets the events with exception.has_esr as zero, KVM will choose an ESR. Specifying exception.has_esr on a system that does not support it will return an error. Settings anything other than the lower 24bits of exception.serror_esr will return an error. ------------------%<------------------ because as Peter points out, this is where people will expect to find this. I'll kick this out as a v9 later today. Thanks! James
