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Subject[PATCH v13 08/12] KVM: x86: Add Intel PT context switch for each vcpu
Date
From: Chao Peng <chao.p.peng@linux.intel.com>

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>
---
arch/x86/include/asm/intel_pt.h | 2 +
arch/x86/kvm/vmx.c | 94 +++++++++++++++++++++++++++++++++++++++++
2 files changed, 96 insertions(+)

diff --git a/arch/x86/include/asm/intel_pt.h b/arch/x86/include/asm/intel_pt.h
index 4727584..eabbdbc 100644
--- a/arch/x86/include/asm/intel_pt.h
+++ b/arch/x86/include/asm/intel_pt.h
@@ -8,6 +8,8 @@
#define PT_MODE_SYSTEM 0
#define PT_MODE_HOST_GUEST 1

+#define RTIT_ADDR_RANGE 4
+
enum pt_capabilities {
PT_CAP_max_subleaf = 0,
PT_CAP_cr3_filtering,
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 692154c..d8480a6 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -978,6 +978,24 @@ struct vmx_msrs {
struct vmx_msr_entry val[NR_AUTOLOAD_MSRS];
};

+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;
+};
+
struct vcpu_vmx {
struct kvm_vcpu vcpu;
unsigned long host_rsp;
@@ -1071,6 +1089,8 @@ struct vcpu_vmx {
u64 msr_ia32_feature_control;
u64 msr_ia32_feature_control_valid_bits;
u64 ept_pointer;
+
+ struct pt_desc pt_desc;
};

enum segment_cache_field {
@@ -2899,6 +2919,69 @@ 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);
+}
+
static void vmx_prepare_switch_to_guest(struct kvm_vcpu *vcpu)
{
struct vcpu_vmx *vmx = to_vmx(vcpu);
@@ -6749,6 +6832,13 @@ 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)
@@ -11260,6 +11350,8 @@ 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);
@@ -11459,6 +11551,8 @@ 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
--
1.8.3.1
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