KVM: x86: Add Intel PT context switch for each vcpu

Load/Store Intel Processor Trace register in context switch.
MSR IA32_RTIT_CTL is loaded/stored automatically from VMCS.
In Host-Guest mode, we need load/resore PT MSRs only when PT
is enabled in guest.

Signed-off-by: Chao Peng <chao.p.peng@linux.intel.com>
Signed-off-by: Luwei Kang <luwei.kang@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/vmx/vmx.c

@@ -936,6 +936,69 @@ static unsigned long segment_base(u16 selector)
 }
 #endif
 
+static inline void pt_load_msr(struct pt_ctx *ctx, u32 addr_range)
+{
+	u32 i;
+
+	wrmsrl(MSR_IA32_RTIT_STATUS, ctx->status);
+	wrmsrl(MSR_IA32_RTIT_OUTPUT_BASE, ctx->output_base);
+	wrmsrl(MSR_IA32_RTIT_OUTPUT_MASK, ctx->output_mask);
+	wrmsrl(MSR_IA32_RTIT_CR3_MATCH, ctx->cr3_match);
+	for (i = 0; i < addr_range; i++) {
+		wrmsrl(MSR_IA32_RTIT_ADDR0_A + i * 2, ctx->addr_a[i]);
+		wrmsrl(MSR_IA32_RTIT_ADDR0_B + i * 2, ctx->addr_b[i]);
+	}
+}
+
+static inline void pt_save_msr(struct pt_ctx *ctx, u32 addr_range)
+{
+	u32 i;
+
+	rdmsrl(MSR_IA32_RTIT_STATUS, ctx->status);
+	rdmsrl(MSR_IA32_RTIT_OUTPUT_BASE, ctx->output_base);
+	rdmsrl(MSR_IA32_RTIT_OUTPUT_MASK, ctx->output_mask);
+	rdmsrl(MSR_IA32_RTIT_CR3_MATCH, ctx->cr3_match);
+	for (i = 0; i < addr_range; i++) {
+		rdmsrl(MSR_IA32_RTIT_ADDR0_A + i * 2, ctx->addr_a[i]);
+		rdmsrl(MSR_IA32_RTIT_ADDR0_B + i * 2, ctx->addr_b[i]);
+	}
+}
+
+static void pt_guest_enter(struct vcpu_vmx *vmx)
+{
+	if (pt_mode == PT_MODE_SYSTEM)
+		return;
+
+	/* Save host state before VM entry */
+	rdmsrl(MSR_IA32_RTIT_CTL, vmx->pt_desc.host.ctl);
+
+	/*
+	 * Set guest state of MSR_IA32_RTIT_CTL MSR (PT will be disabled
+	 * on VM entry when it has been disabled in guest before).
+	 */
+	vmcs_write64(GUEST_IA32_RTIT_CTL, vmx->pt_desc.guest.ctl);
+
+	if (vmx->pt_desc.guest.ctl & RTIT_CTL_TRACEEN) {
+		wrmsrl(MSR_IA32_RTIT_CTL, 0);
+		pt_save_msr(&vmx->pt_desc.host, vmx->pt_desc.addr_range);
+		pt_load_msr(&vmx->pt_desc.guest, vmx->pt_desc.addr_range);
+	}
+}
+
+static void pt_guest_exit(struct vcpu_vmx *vmx)
+{
+	if (pt_mode == PT_MODE_SYSTEM)
+		return;
+
+	if (vmx->pt_desc.guest.ctl & RTIT_CTL_TRACEEN) {
+		pt_save_msr(&vmx->pt_desc.guest, vmx->pt_desc.addr_range);
+		pt_load_msr(&vmx->pt_desc.host, vmx->pt_desc.addr_range);
+	}
+
+	/* Reload host state (IA32_RTIT_CTL will be cleared on VM exit). */
+	wrmsrl(MSR_IA32_RTIT_CTL, vmx->pt_desc.host.ctl);
+}
+
 void vmx_prepare_switch_to_guest(struct kvm_vcpu *vcpu)
 {
 	struct vcpu_vmx *vmx = to_vmx(vcpu);
@@ -3814,6 +3877,13 @@ static void vmx_vcpu_setup(struct vcpu_vmx *vmx)
 
 	if (cpu_has_vmx_encls_vmexit())
 		vmcs_write64(ENCLS_EXITING_BITMAP, -1ull);
+
+	if (pt_mode == PT_MODE_HOST_GUEST) {
+		memset(&vmx->pt_desc, 0, sizeof(vmx->pt_desc));
+		/* Bit[6~0] are forced to 1, writes are ignored. */
+		vmx->pt_desc.guest.output_mask = 0x7F;
+		vmcs_write64(GUEST_IA32_RTIT_CTL, 0);
+	}
 }
 
 static void vmx_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event)
@@ -6115,6 +6185,8 @@ static void __noclone vmx_vcpu_run(struct kvm_vcpu *vcpu)
 	    vcpu->arch.pkru != vmx->host_pkru)
 		__write_pkru(vcpu->arch.pkru);
 
+	pt_guest_enter(vmx);
+
 	atomic_switch_perf_msrs(vmx);
 
 	vmx_update_hv_timer(vcpu);
@@ -6314,6 +6386,8 @@ static void __noclone vmx_vcpu_run(struct kvm_vcpu *vcpu)
 				  | (1 << VCPU_EXREG_CR3));
 	vcpu->arch.regs_dirty = 0;
 
+	pt_guest_exit(vmx);
+
 	/*
 	 * eager fpu is enabled if PKEY is supported and CR4 is switched
 	 * back on host, so it is safe to read guest PKRU from current

arch/x86/kvm/vmx/vmx.h

@@ -66,6 +66,25 @@ struct pi_desc {
 	u32 rsvd[6];
 } __aligned(64);
 
+#define RTIT_ADDR_RANGE		4
+
+struct pt_ctx {
+	u64 ctl;
+	u64 status;
+	u64 output_base;
+	u64 output_mask;
+	u64 cr3_match;
+	u64 addr_a[RTIT_ADDR_RANGE];
+	u64 addr_b[RTIT_ADDR_RANGE];
+};
+
+struct pt_desc {
+	u64 ctl_bitmask;
+	u32 addr_range;
+	u32 caps[PT_CPUID_REGS_NUM * PT_CPUID_LEAVES];
+	struct pt_ctx host;
+	struct pt_ctx guest;
+};
 
 /*
  * The nested_vmx structure is part of vcpu_vmx, and holds information we need
@@ -249,6 +268,8 @@ struct vcpu_vmx {
 	u64 msr_ia32_feature_control;
 	u64 msr_ia32_feature_control_valid_bits;
 	u64 ept_pointer;
+
+	struct pt_desc pt_desc;
 };
 
 enum ept_pointers_status {