linux-kernel - [GIT PULL] KVM: x86: Changes for 6.15

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Message-ID: <20250318180303.283401-1-seanjc@google.com>
Date: Tue, 18 Mar 2025 11:02:55 -0700
From: Sean Christopherson <seanjc@...gle.com>
To: Paolo Bonzini <pbonzini@...hat.com>
Cc: kvm@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Sean Christopherson <seanjc@...gle.com>
Subject: [GIT PULL] KVM: x86: Changes for 6.15

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