From: Paul Durrant pdurrant@amazon.com
If the guest does not explicitly set the GPA of vcpu_info structure in memory then, for guests with 32 vCPUs or fewer, the vcpu_info embedded in the shared_info page may be used. As described in a previous commit, the shared_info page is an overlay at a fixed HVA within the VMM, so in this case it also more optimal to activate the vcpu_info cache with a fixed HVA to avoid unnecessary invalidation if the guest memory layout is modified.
Signed-off-by: Paul Durrant pdurrant@amazon.com Reviewed-by: David Woodhouse dwmw@amazon.co.uk --- Cc: David Woodhouse dwmw2@infradead.org Cc: Sean Christopherson seanjc@google.com Cc: Paolo Bonzini pbonzini@redhat.com Cc: Thomas Gleixner tglx@linutronix.de Cc: Ingo Molnar mingo@redhat.com Cc: Borislav Petkov bp@alien8.de Cc: Dave Hansen dave.hansen@linux.intel.com Cc: "H. Peter Anvin" hpa@zytor.com Cc: x86@kernel.org
v13: - Patch title change.
v8: - Re-base.
v5: - New in this version. --- Documentation/virt/kvm/api.rst | 26 +++++++++++++++++++++----- arch/x86/kvm/xen.c | 34 ++++++++++++++++++++++++++++------ include/uapi/linux/kvm.h | 3 +++ 3 files changed, 52 insertions(+), 11 deletions(-)
diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst index 3372be85b335..bd93cafd3e4e 100644 --- a/Documentation/virt/kvm/api.rst +++ b/Documentation/virt/kvm/api.rst @@ -5523,11 +5523,12 @@ KVM_XEN_ATTR_TYPE_SHARED_INFO Sets the guest physical frame number at which the Xen shared_info page resides. Note that although Xen places vcpu_info for the first 32 vCPUs in the shared_info page, KVM does not automatically do so - and instead requires that KVM_XEN_VCPU_ATTR_TYPE_VCPU_INFO be used - explicitly even when the vcpu_info for a given vCPU resides at the - "default" location in the shared_info page. This is because KVM may - not be aware of the Xen CPU id which is used as the index into the - vcpu_info[] array, so may know the correct default location. + and instead requires that KVM_XEN_VCPU_ATTR_TYPE_VCPU_INFO or + KVM_XEN_VCPU_ATTR_TYPE_VCPU_INFO_HVA be used explicitly even when + the vcpu_info for a given vCPU resides at the "default" location + in the shared_info page. This is because KVM may not be aware of + the Xen CPU id which is used as the index into the vcpu_info[] + array, so may know the correct default location.
Note that the shared_info page may be constantly written to by KVM; it contains the event channel bitmap used to deliver interrupts to @@ -5649,6 +5650,21 @@ KVM_XEN_VCPU_ATTR_TYPE_VCPU_INFO on dirty logging. Setting the gpa to KVM_XEN_INVALID_GPA will disable the vcpu_info.
+KVM_XEN_VCPU_ATTR_TYPE_VCPU_INFO_HVA + If the KVM_XEN_HVM_CONFIG_SHARED_INFO_HVA flag is also set in the + Xen capabilities, then this attribute may be used to set the + userspace address of the vcpu_info for a given vCPU. It should + only be used when the vcpu_info resides at the "default" location + in the shared_info page. In this case it is safe to assume the + userspace address will not change, because the shared_info page is + an overlay on guest memory and remains at a fixed host address + regardless of where it is mapped in guest physical address space + and hence unnecessary invalidation of an internal cache may be + avoided if the guest memory layout is modified. + If the vcpu_info does not reside at the "default" location then + it is not guaranteed to remain at the same host address and + hence the aforementioned cache invalidation is required. + KVM_XEN_VCPU_ATTR_TYPE_VCPU_TIME_INFO Sets the guest physical address of an additional pvclock structure for a given vCPU. This is typically used for guest vsyscall support. diff --git a/arch/x86/kvm/xen.c b/arch/x86/kvm/xen.c index 6fb268e424fa..4e79cc68e0a9 100644 --- a/arch/x86/kvm/xen.c +++ b/arch/x86/kvm/xen.c @@ -784,20 +784,33 @@ int kvm_xen_vcpu_set_attr(struct kvm_vcpu *vcpu, struct kvm_xen_vcpu_attr *data)
switch (data->type) { case KVM_XEN_VCPU_ATTR_TYPE_VCPU_INFO: + case KVM_XEN_VCPU_ATTR_TYPE_VCPU_INFO_HVA: /* No compat necessary here. */ BUILD_BUG_ON(sizeof(struct vcpu_info) != sizeof(struct compat_vcpu_info)); BUILD_BUG_ON(offsetof(struct vcpu_info, time) != offsetof(struct compat_vcpu_info, time));
- if (data->u.gpa == KVM_XEN_INVALID_GPA) { - kvm_gpc_deactivate(&vcpu->arch.xen.vcpu_info_cache); - r = 0; - break; + if (data->type == KVM_XEN_VCPU_ATTR_TYPE_VCPU_INFO) { + if (data->u.gpa == KVM_XEN_INVALID_GPA) { + kvm_gpc_deactivate(&vcpu->arch.xen.vcpu_info_cache); + r = 0; + break; + } + + r = kvm_gpc_activate(&vcpu->arch.xen.vcpu_info_cache, + data->u.gpa, sizeof(struct vcpu_info)); + } else { + if (data->u.hva == 0) { + kvm_gpc_deactivate(&vcpu->arch.xen.vcpu_info_cache); + r = 0; + break; + } + + r = kvm_gpc_activate_hva(&vcpu->arch.xen.vcpu_info_cache, + data->u.hva, sizeof(struct vcpu_info)); }
- r = kvm_gpc_activate(&vcpu->arch.xen.vcpu_info_cache, - data->u.gpa, sizeof(struct vcpu_info)); if (!r) kvm_make_request(KVM_REQ_CLOCK_UPDATE, vcpu);
@@ -1026,6 +1039,15 @@ int kvm_xen_vcpu_get_attr(struct kvm_vcpu *vcpu, struct kvm_xen_vcpu_attr *data) r = 0; break;
+ case KVM_XEN_VCPU_ATTR_TYPE_VCPU_INFO_HVA: + if (vcpu->arch.xen.vcpu_info_cache.active && + vcpu->arch.xen.vcpu_info_cache.gpa == KVM_XEN_INVALID_GPA) + data->u.hva = vcpu->arch.xen.vcpu_info_cache.uhva; + else + data->u.hva = 0; + r = 0; + break; + case KVM_XEN_VCPU_ATTR_TYPE_VCPU_TIME_INFO: if (vcpu->arch.xen.vcpu_time_info_cache.active) data->u.gpa = vcpu->arch.xen.vcpu_time_info_cache.gpa; diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h index ac5caba313d1..d2665319db6e 100644 --- a/include/uapi/linux/kvm.h +++ b/include/uapi/linux/kvm.h @@ -1809,6 +1809,7 @@ struct kvm_xen_vcpu_attr { union { __u64 gpa; #define KVM_XEN_INVALID_GPA ((__u64)-1) + __u64 hva; __u64 pad[8]; struct { __u64 state; @@ -1839,6 +1840,8 @@ struct kvm_xen_vcpu_attr { #define KVM_XEN_VCPU_ATTR_TYPE_VCPU_ID 0x6 #define KVM_XEN_VCPU_ATTR_TYPE_TIMER 0x7 #define KVM_XEN_VCPU_ATTR_TYPE_UPCALL_VECTOR 0x8 +/* Available with KVM_CAP_XEN_HVM / KVM_XEN_HVM_CONFIG_SHARED_INFO_HVA */ +#define KVM_XEN_VCPU_ATTR_TYPE_VCPU_INFO_HVA 0x9
/* Secure Encrypted Virtualization command */ enum sev_cmd_id {