Re: [RFC 09/33] KVM: x86: hyper-v: Introduce per-VTL vcpu helpers

From: Alexander Graf
Date: Wed Nov 08 2023 - 07:22:13 EST



On 08.11.23 12:17, Nicolas Saenz Julienne wrote:
Introduce two helper functions. The first one queries a vCPU's VTL
level, the second one, given a struct kvm_vcpu and VTL pair, returns the
corresponding 'sibling' struct kvm_vcpu at the right VTL.

We keep track of each VTL's state by having a distinct struct kvm_vpcu
for each level. VTL-vCPUs that belong to the same guest CPU share the
same physical APIC id, but belong to different APIC groups where the
apic group represents the vCPU's VTL.

Signed-off-by: Nicolas Saenz Julienne <nsaenz@xxxxxxxxxx>
---
arch/x86/kvm/hyperv.h | 18 ++++++++++++++++++
1 file changed, 18 insertions(+)

diff --git a/arch/x86/kvm/hyperv.h b/arch/x86/kvm/hyperv.h
index 2bfed69ba0db..5433107e7cc8 100644
--- a/arch/x86/kvm/hyperv.h
+++ b/arch/x86/kvm/hyperv.h
@@ -23,6 +23,7 @@
#include <linux/kvm_host.h>
#include "x86.h"
+#include "lapic.h"
/* "Hv#1" signature */
#define HYPERV_CPUID_SIGNATURE_EAX 0x31237648
@@ -83,6 +84,23 @@ static inline struct kvm_hv_syndbg *to_hv_syndbg(struct kvm_vcpu *vcpu)
return &vcpu->kvm->arch.hyperv.hv_syndbg;
}
+static inline struct kvm_vcpu *kvm_hv_get_vtl_vcpu(struct kvm_vcpu *vcpu, int vtl)
+{
+ struct kvm *kvm = vcpu->kvm;
+ u32 target_id = kvm_apic_id(vcpu);
+
+ kvm_apic_id_set_group(kvm, vtl, &target_id);
+ if (vcpu->vcpu_id == target_id)
+ return vcpu;
+
+ return kvm_get_vcpu_by_id(kvm, target_id);
+}
+
+static inline u8 kvm_hv_get_active_vtl(struct kvm_vcpu *vcpu)
+{
+ return kvm_apic_group(vcpu);


Shouldn't this check whether VTL is active? If someone wants to use APIC groups for a different purpose in the future, they'd suddenly find themselves in VTL code paths in other code (such as memory protections), no?

Alex





Amazon Development Center Germany GmbH
Krausenstr. 38
10117 Berlin
Geschaeftsfuehrung: Christian Schlaeger, Jonathan Weiss
Eingetragen am Amtsgericht Charlottenburg unter HRB 149173 B
Sitz: Berlin
Ust-ID: DE 289 237 879