KVM: x86/xen: update Xen CPUID Leaf 4 (tsc info) sub-leaves, if present

The scaling information in subleaf 1 should match the values set by KVM in
the 'vcpu_info' sub-structure 'time_info' (a.k.a. pvclock_vcpu_time_info)
which is shared with the guest, but is not directly available to the VMM.
The offset values are not set since a TSC offset is already applied.
The TSC frequency should also be set in sub-leaf 2.

Signed-off-by: Paul Durrant <pdurrant@amazon.com>
Reviewed-by: David Woodhouse <dwmw@amazon.co.uk>
Link: https://lore.kernel.org/r/20230106103600.528-3-pdurrant@amazon.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 0e5da33..8b38a4c 100644 (file)
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -703,6 +703,7 @@ struct kvm_vcpu_xen {
        struct hrtimer timer;
        int poll_evtchn;
        struct timer_list poll_timer;
+       struct kvm_hypervisor_cpuid cpuid;
 };
 
 struct kvm_queued_exception {

diff --git a/arch/x86/include/asm/xen/hypervisor.h b/arch/x86/include/asm/xen/hypervisor.h
index 16f548a..5fc35f8 100644 (file)
--- a/arch/x86/include/asm/xen/hypervisor.h
+++ b/arch/x86/include/asm/xen/hypervisor.h
@@ -38,9 +38,11 @@ extern struct start_info *xen_start_info;
 
 #include <asm/processor.h>
 
+#define XEN_SIGNATURE "XenVMMXenVMM"
+
 static inline uint32_t xen_cpuid_base(void)
 {
-       return hypervisor_cpuid_base("XenVMMXenVMM", 2);
+       return hypervisor_cpuid_base(XEN_SIGNATURE, 2);
 }
 
 struct pci_dev;

diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index c5c6eef..8f8edea 100644 (file)
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -26,6 +26,7 @@
 #include "mmu.h"
 #include "trace.h"
 #include "pmu.h"
+#include "xen.h"
 
 /*
  * Unlike "struct cpuinfo_x86.x86_capability", kvm_cpu_caps doesn't need to be
@@ -443,6 +444,7 @@ static int kvm_set_cpuid(struct kvm_vcpu *vcpu, struct kvm_cpuid_entry2 *e2,
        vcpu->arch.cpuid_nent = nent;
 
        vcpu->arch.kvm_cpuid = kvm_get_hypervisor_cpuid(vcpu, KVM_SIGNATURE);
+       vcpu->arch.xen.cpuid = kvm_get_hypervisor_cpuid(vcpu, XEN_SIGNATURE);
        kvm_vcpu_after_set_cpuid(vcpu);
 
        return 0;

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index fc3ae3c..65b401e 100644 (file)
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3161,6 +3161,7 @@ static int kvm_guest_time_update(struct kvm_vcpu *v)
                                   &vcpu->hv_clock.tsc_shift,
                                   &vcpu->hv_clock.tsc_to_system_mul);
                vcpu->hw_tsc_khz = tgt_tsc_khz;
+               kvm_xen_update_tsc_info(v);
        }
 
        vcpu->hv_clock.tsc_timestamp = tsc_timestamp;

diff --git a/arch/x86/kvm/xen.c b/arch/x86/kvm/xen.c
index 2681e20..40edf4d 100644 (file)
--- a/arch/x86/kvm/xen.c
+++ b/arch/x86/kvm/xen.c
@@ -23,6 +23,9 @@
 #include <xen/interface/event_channel.h>
 #include <xen/interface/sched.h>
 
+#include <asm/xen/cpuid.h>
+
+#include "cpuid.h"
 #include "trace.h"
 
 static int kvm_xen_set_evtchn(struct kvm_xen_evtchn *xe, struct kvm *kvm);
@@ -2077,6 +2080,29 @@ void kvm_xen_destroy_vcpu(struct kvm_vcpu *vcpu)
        del_timer_sync(&vcpu->arch.xen.poll_timer);
 }
 
+void kvm_xen_update_tsc_info(struct kvm_vcpu *vcpu)
+{
+       struct kvm_cpuid_entry2 *entry;
+       u32 function;
+
+       if (!vcpu->arch.xen.cpuid.base)
+               return;
+
+       function = vcpu->arch.xen.cpuid.base | XEN_CPUID_LEAF(3);
+       if (function > vcpu->arch.xen.cpuid.limit)
+               return;
+
+       entry = kvm_find_cpuid_entry_index(vcpu, function, 1);
+       if (entry) {
+               entry->ecx = vcpu->arch.hv_clock.tsc_to_system_mul;
+               entry->edx = vcpu->arch.hv_clock.tsc_shift;
+       }
+
+       entry = kvm_find_cpuid_entry_index(vcpu, function, 2);
+       if (entry)
+               entry->eax = vcpu->arch.hw_tsc_khz;
+}
+
 void kvm_xen_init_vm(struct kvm *kvm)
 {
        mutex_init(&kvm->arch.xen.xen_lock);

diff --git a/arch/x86/kvm/xen.h b/arch/x86/kvm/xen.h
index ea33d80..f8f1fe2 100644 (file)
--- a/arch/x86/kvm/xen.h
+++ b/arch/x86/kvm/xen.h
@@ -9,6 +9,8 @@
 #ifndef __ARCH_X86_KVM_XEN_H__
 #define __ARCH_X86_KVM_XEN_H__
 
+#include <asm/xen/hypervisor.h>
+
 #ifdef CONFIG_KVM_XEN
 #include <linux/jump_label_ratelimit.h>
 
@@ -32,6 +34,7 @@ int kvm_xen_set_evtchn_fast(struct kvm_xen_evtchn *xe,
 int kvm_xen_setup_evtchn(struct kvm *kvm,
                         struct kvm_kernel_irq_routing_entry *e,
                         const struct kvm_irq_routing_entry *ue);
+void kvm_xen_update_tsc_info(struct kvm_vcpu *vcpu);
 
 static inline bool kvm_xen_msr_enabled(struct kvm *kvm)
 {
@@ -135,6 +138,10 @@ static inline bool kvm_xen_timer_enabled(struct kvm_vcpu *vcpu)
 {
        return false;
 }
+
+static inline void kvm_xen_update_tsc_info(struct kvm_vcpu *vcpu)
+{
+}
 #endif
 
 int kvm_xen_hypercall(struct kvm_vcpu *vcpu);