On Tue, Mar 18, 2025 at 7:03 PM Sean Christopherson <seanjc@xxxxxxxxxx> wrote:
> There are two conflicts between the PV clock pull request and the Xen
> pull request.
>
> 1. The Xen branch moves Xen TSC leaf updates to CPUID emulation, and the PV
> clock branch renames the fields in kvm_vcpu_arch that are used to update
> the Xen leafs. After the dust settles, kvm_cpuid() should look like:
>
> } else if (IS_ENABLED(CONFIG_KVM_XEN) &&
> kvm_xen_is_tsc_leaf(vcpu, function)) {
> /*
> * Update guest TSC frequency information if necessary.
> * Ignore failures, there is no sane value that can be
> * provided if KVM can't get the TSC frequency.
> */
> if (kvm_check_request(KVM_REQ_CLOCK_UPDATE, vcpu))
> kvm_guest_time_update(vcpu);
>
> if (index == 1) {
> *ecx = vcpu->arch.pvclock_tsc_mul;
> *edx = vcpu->arch.pvclock_tsc_shift;
> } else if (index == 2) {
> *eax = vcpu->arch.hw_tsc_khz;
> }
> }
>
> 2. The Xen branch moves and renames xen_hvm_config so that its xen.hvm_config,
> while PV clock branch shuffles use of xen_hvm_config/xen.hvm_config flags.
> The resulting code in kvm_guest_time_update() should look like:
>
> #ifdef CONFIG_KVM_XEN
> /*
> * For Xen guests we may need to override PVCLOCK_TSC_STABLE_BIT as unless
> * explicitly told to use TSC as its clocksource Xen will not set this bit.
> * This default behaviour led to bugs in some guest kernels which cause
> * problems if they observe PVCLOCK_TSC_STABLE_BIT in the pvclock flags.
> *
> * Note! Clear TSC_STABLE only for Xen clocks, i.e. the order matters!
> */
> if (ka->xen.hvm_config.flags & KVM_XEN_HVM_CONFIG_PVCLOCK_TSC_UNSTABLE)
> hv_clock.flags &= ~PVCLOCK_TSC_STABLE_BIT;
>
> if (vcpu->xen.vcpu_info_cache.active)
> kvm_setup_guest_pvclock(&hv_clock, v, &vcpu->xen.vcpu_info_cache,
> offsetof(struct compat_vcpu_info, time));
> if (vcpu->xen.vcpu_time_info_cache.active)
> kvm_setup_guest_pvclock(&hv_clock, v, &vcpu->xen.vcpu_time_info_cache, 0);
> #endif
Thanks, pulled everything to kvm/queue. I assume you want me to put
the following on top:
* KVM: Drop kvm_arch_sync_events() now that all implementations are nops
* KVM: x86: Fold guts of kvm_arch_sync_events() into kvm_arch_pre_destroy_vm()
* KVM: x86: Unload MMUs during vCPU destruction, not before
* KVM: Assert that a destroyed/freed vCPU is no longer visible
* KVM: x86: Don't load/put vCPU when unloading its MMU during teardown
Paolo
