On Wed, Jan 17, 2018 at 07:03:13PM +0100, Paolo Bonzini wrote: > On 17/01/2018 15:27, Radim Krčmář wrote: > > 2018-01-17 08:51+1100, Paul Mackerras: > >> On Tue, Jan 16, 2018 at 03:45:11PM +0100, Paolo Bonzini wrote: > >>> On 16/01/2018 01:59, Paul Mackerras wrote: > >>>> This adds a new ioctl, KVM_PPC_GET_CPU_CHAR, that gives userspace > >>>> information about the underlying machine's level of vulnerability > >>>> to the recently announced vulnerabilities CVE-2017-5715, > >>>> CVE-2017-5753 and CVE-2017-5754, and whether the machine provides > >>>> instructions to assist software to work around the vulnerabilities. > >>>> > >>>> The ioctl returns two u64 words describing characteristics of the > >>>> CPU and required software behaviour respectively, plus two mask > >>>> words which indicate which bits have been filled in by the kernel, > >>>> for extensibility. The bit definitions are the same as for the > >>>> new H_GET_CPU_CHARACTERISTICS hypercall. > >>>> > >>>> There is also a new capability, KVM_CAP_PPC_GET_CPU_CHAR, which > >>>> indicates whether the new ioctl is available. > >>>> > >>>> Signed-off-by: Paul Mackerras <paulus@xxxxxxxxxx> > >>>> --- > >>> > >>> Thanks, looks good. Would you like this in 4.15? > >> > >> Yes please. Will you just apply the patch, or do you want me to put > >> it in a branch for you to pull? > > > > I can apply it directly. > > > > Do I understand correctly that the interface is a KVM hypercall because > ^^^^^^^^^ > > ioctl? > > > we need to forward this information into guests and other userspace can > > do nothing with the information? > > There will probably be someone else that can consume it sooner or later. > sysfs or /proc/cpuinfo probably would be a better interface. But I > guess KVM is the prime consumer... Right, it is. KVM needs all the bits, and I don't see why any other userspace consumer would need more than a couple of them. Paul.
