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Subject[PATCH v8 03/14] KVM/x86: KVM_CAP_X86_GUEST_LBR
Date
Introduce KVM_CAP_X86_GUEST_LBR to allow per-VM enabling of the guest
lbr feature.

Signed-off-by: Wei Wang <wei.w.wang@intel.com>
---
Documentation/virt/kvm/api.txt | 26 ++++++++++++++++++++++++++
arch/x86/include/asm/kvm_host.h | 2 ++
arch/x86/kvm/x86.c | 16 ++++++++++++++++
include/uapi/linux/kvm.h | 1 +
4 files changed, 45 insertions(+)

diff --git a/Documentation/virt/kvm/api.txt b/Documentation/virt/kvm/api.txt
index 2d06776..64632a8 100644
--- a/Documentation/virt/kvm/api.txt
+++ b/Documentation/virt/kvm/api.txt
@@ -5046,6 +5046,32 @@ it hard or impossible to use it correctly. The availability of
KVM_CAP_MANUAL_DIRTY_LOG_PROTECT2 signals that those bugs are fixed.
Userspace should not try to use KVM_CAP_MANUAL_DIRTY_LOG_PROTECT.

+7.19 KVM_CAP_X86_GUEST_LBR
+Architectures: x86
+Parameters: args[0] whether feature should be enabled or not
+ args[1] pointer to the userspace memory to load the lbr stack info
+
+The lbr stack info is described by
+struct x86_perf_lbr_stack {
+ unsigned int nr;
+ unsigned int tos;
+ unsigned int from;
+ unsigned int to;
+ unsigned int info;
+};
+
+@nr: number of lbr stack entries
+@tos: index of the top of stack msr
+@from: index of the msr that stores a branch source address
+@to: index of the msr that stores a branch destination address
+@info: index of the msr that stores lbr related flags
+
+Enabling this capability allows guest accesses to the lbr feature. Otherwise,
+#GP will be injected to the guest when it accesses to the lbr related msrs.
+
+After the feature is enabled, before exiting to userspace, kvm handlers should
+fill the lbr stack info into the userspace memory pointed by args[1].
+
8. Other capabilities.
----------------------

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 7b0a4ee..d29dddd 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -875,6 +875,7 @@ struct kvm_arch {
atomic_t vapics_in_nmi_mode;
struct mutex apic_map_lock;
struct kvm_apic_map *apic_map;
+ struct x86_perf_lbr_stack lbr_stack;

bool apic_access_page_done;

@@ -884,6 +885,7 @@ struct kvm_arch {
bool hlt_in_guest;
bool pause_in_guest;
bool cstate_in_guest;
+ bool lbr_in_guest;

unsigned long irq_sources_bitmap;
s64 kvmclock_offset;
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index c6d951c..e1eb1be 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3129,6 +3129,9 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
case KVM_CAP_EXCEPTION_PAYLOAD:
r = 1;
break;
+ case KVM_CAP_X86_GUEST_LBR:
+ r = sizeof(struct x86_perf_lbr_stack);
+ break;
case KVM_CAP_SYNC_REGS:
r = KVM_SYNC_X86_VALID_FIELDS;
break;
@@ -4670,6 +4673,19 @@ int kvm_vm_ioctl_enable_cap(struct kvm *kvm,
kvm->arch.exception_payload_enabled = cap->args[0];
r = 0;
break;
+ case KVM_CAP_X86_GUEST_LBR:
+ r = -EINVAL;
+ if (cap->args[0] &&
+ x86_perf_get_lbr_stack(&kvm->arch.lbr_stack))
+ break;
+
+ if (copy_to_user((void __user *)cap->args[1],
+ &kvm->arch.lbr_stack,
+ sizeof(struct x86_perf_lbr_stack)))
+ break;
+ kvm->arch.lbr_in_guest = cap->args[0];
+ r = 0;
+ break;
default:
r = -EINVAL;
break;
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index 5e3f12d..dd53edc 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -996,6 +996,7 @@ struct kvm_ppc_resize_hpt {
#define KVM_CAP_ARM_PTRAUTH_ADDRESS 171
#define KVM_CAP_ARM_PTRAUTH_GENERIC 172
#define KVM_CAP_PMU_EVENT_FILTER 173
+#define KVM_CAP_X86_GUEST_LBR 174

#ifdef KVM_CAP_IRQ_ROUTING

--
2.7.4
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