Messages in this thread | | | Subject | Re: [PATCH v1 01/24] LoongArch: KVM: Implement kvm module related interface | From | Tianrui Zhao <> | Date | Fri, 17 Feb 2023 09:27:50 +0800 |
| |
在 2023年02月17日 03:34, Oliver Upton 写道: > On Tue, Feb 14, 2023 at 09:00:50PM +0800, Tianrui Zhao wrote: >> 在 2023年02月14日 17:58, Greg Kroah-Hartman 写道: >>> On Tue, Feb 14, 2023 at 05:00:56PM +0800, Tianrui Zhao wrote: >>>>>> +#define KVM_GET_CSRS _IOWR(KVMIO, 0xc5, struct kvm_csrs) >>>>>> +#define KVM_SET_CSRS _IOW(KVMIO, 0xc6, struct kvm_csrs) >>>>> Why does this arch need new ioctls? >>>> We want to use this ioctl to access multiple csrs at one time. If without >>>> this, we only access one csr. >>> What is wrong with accessing only one csr at a time? Isn't this what >>> other architectures do? >> Generally, using KVM_GET_ONE_GET ioctl to get one reg, but we want a >> more convenient interface to get serial regs at one time, so we add this >> ioctl. > Have you found register accesses through the KVM_{GET,SET}_ONE_REG > ioctls to actually be a bounding issue? I'd be surprised if that were > actually the case. > > An architecture-neutral implementation was entertained a few years ago > [*], but even then it saved an inconsequential amount of time relative > to the rest of VM serialization (at least for arm64). The one thing that > series got right was to share the plumbing across all architectures that > use the ONE_REG interface (i.e. everyone but x86). > > If you have data that supports the thesis that a batched ioctl is > useful then please do share. But in any case this should not use an ioctl > tied down to a single architecture. > > [*] https://lore.kernel.org/kvm/20201120125616.14436-1-darkhan@amazon.com/ >
Thanks for your explanation, and we have decided to remove this ioctls.
thanks, Tianrui Zhao
| |