Ping - let me know if there's anything particularly controversial, unclear, etc. about these patches or if I can do anything to make reviewing easier.
Thanks! On Fri, 22 Sept 2023 at 16:09, Phil Dennis-Jordan <p...@philjordan.eu> wrote: > > This is a series of semi-related patches for the x86 macOS > Hypervisor.framework > (hvf) accelerator backend. The intention is to make VMs run slightly more > efficiently on macOS host machines. They have been subject to some months of > CI workloads with macOS guest VMs without issues and they seem to give a few > percent performance improvement. (Though this varies greatly with the type of > workload.) > > Patch 1 enables the INVTSC CPUID bit when running with hvf. This can enable > some optimisations in the guest OS, and I've not found any reason it shouldn't > be allowed for hvf based hosts. > > Patch 2 fixes hvf_kick_vcpu_thread so it actually forces a VM exit instead of > doing nothing. I guess this previously didn't cause any huge issues because > hvf's hv_vcpu_run() would exit so extremely frequently on its own accord. The > temp variable is needed because the pointer expected by the > hv_vcpu_interrupt() > call doesn't match the fd field's type in the hvf accel's struct > AccelCPUState. > I'm unsure if it would be better to change that struct field to the relevant > architecture's handle types, hv_vcpuid_t (x86, unsigned int) and hv_vcpu_t > (aarch64, uint64_t), perhaps via an intermediate typedef? > > Patch 3, which replaces the call to hv_vcpu_run() with the more modern > hv_vcpu_run_until() for running the guest vCPU. The newer API is available > from macOS 10.15 host systems onwards. This call causes significantly fewer > VM exits, which also means we really need that exit-forcing interrupt from > patch 2. The reduction in VM exits means less overhead from exits and less > contention on the BQL. Using hv_vcpu_run_until() is also a prerequisite for > using certain newer hvf features, though this patchset doesn't use any. > > Patches 2 & 3 must therefore be applied in that order, patch 1 is independent. > > This work has been sponsored by Sauce Labs Inc. > > Phil Dennis-Jordan (3): > i386: hvf: Adds support for INVTSC cpuid bit > i386: hvf: In kick_vcpu use hv_vcpu_interrupt to force exit > i386: hvf: Updates API usage to use modern vCPU run function > > target/i386/hvf/hvf.c | 26 +++++++++++++++++++++++++- > target/i386/hvf/x86_cpuid.c | 4 ++++ > 2 files changed, 29 insertions(+), 1 deletion(-) > > -- > 2.36.1 >
