[PATCH v2 6/6] KVM: x86: Update vPMCs when retiring branch instructions

From: Like Xu
Date: Tue Nov 30 2021 - 02:42:55 EST

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From: Jim Mattson <jmattson@xxxxxxxxxx>

When KVM retires a guest branch instruction through emulation,
increment any vPMCs that are configured to monitor "branch
instructions retired," and update the sample period of those counters
so that they will overflow at the right time.

Signed-off-by: Eric Hankland <ehankland@xxxxxxxxxx>
[jmattson:
- Split the code to increment "branch instructions retired" into a
separate commit.
- Moved/consolidated the calls to kvm_pmu_trigger_event() in the
emulation of VMLAUNCH/VMRESUME to accommodate the evolution of
that code.
]
Fixes: f5132b01386b ("KVM: Expose a version 2 architectural PMU to a guests")
Signed-off-by: Jim Mattson <jmattson@xxxxxxxxxx>
---
arch/x86/kvm/emulate.c | 55 +++++++++++++++++++++-----------------
arch/x86/kvm/kvm_emulate.h | 1 +
arch/x86/kvm/vmx/nested.c | 7 +++--
arch/x86/kvm/x86.c | 2 ++
4 files changed, 39 insertions(+), 26 deletions(-)

diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 28b1a4e57827..166a145fc1e6 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -175,6 +175,7 @@
#define No16 ((u64)1 << 53) /* No 16 bit operand */
#define IncSP ((u64)1 << 54) /* SP is incremented before ModRM calc */
#define TwoMemOp ((u64)1 << 55) /* Instruction has two memory operand */
+#define IsBranch ((u64)1 << 56) /* Instruction is considered a branch. */

#define DstXacc (DstAccLo | SrcAccHi | SrcWrite)

@@ -191,8 +192,9 @@
#define FASTOP_SIZE 8

struct opcode {
- u64 flags : 56;
- u64 intercept : 8;
+ u64 flags;
+ u8 intercept;
+ u8 pad[7];
union {
int (*execute)(struct x86_emulate_ctxt *ctxt);
const struct opcode *group;
@@ -4364,10 +4366,10 @@ static const struct opcode group4[] = {
static const struct opcode group5[] = {
F(DstMem | SrcNone | Lock, em_inc),
F(DstMem | SrcNone | Lock, em_dec),
- I(SrcMem | NearBranch, em_call_near_abs),
- I(SrcMemFAddr | ImplicitOps, em_call_far),
- I(SrcMem | NearBranch, em_jmp_abs),
- I(SrcMemFAddr | ImplicitOps, em_jmp_far),
+ I(SrcMem | NearBranch | IsBranch, em_call_near_abs),
+ I(SrcMemFAddr | ImplicitOps | IsBranch, em_call_far),
+ I(SrcMem | NearBranch | IsBranch, em_jmp_abs),
+ I(SrcMemFAddr | ImplicitOps | IsBranch, em_jmp_far),
I(SrcMem | Stack | TwoMemOp, em_push), D(Undefined),
};

@@ -4577,7 +4579,7 @@ static const struct opcode opcode_table[256] = {
I2bvIP(DstDI | SrcDX | Mov | String | Unaligned, em_in, ins, check_perm_in), /* insb, insw/insd */
I2bvIP(SrcSI | DstDX | String, em_out, outs, check_perm_out), /* outsb, outsw/outsd */
/* 0x70 - 0x7F */
- X16(D(SrcImmByte | NearBranch)),
+ X16(D(SrcImmByte | NearBranch | IsBranch)),
/* 0x80 - 0x87 */
G(ByteOp | DstMem | SrcImm, group1),
G(DstMem | SrcImm, group1),
@@ -4596,7 +4598,7 @@ static const struct opcode opcode_table[256] = {
DI(SrcAcc | DstReg, pause), X7(D(SrcAcc | DstReg)),
/* 0x98 - 0x9F */
D(DstAcc | SrcNone), I(ImplicitOps | SrcAcc, em_cwd),
- I(SrcImmFAddr | No64, em_call_far), N,
+ I(SrcImmFAddr | No64 | IsBranch, em_call_far), N,
II(ImplicitOps | Stack, em_pushf, pushf),
II(ImplicitOps | Stack, em_popf, popf),
I(ImplicitOps, em_sahf), I(ImplicitOps, em_lahf),
@@ -4616,17 +4618,19 @@ static const struct opcode opcode_table[256] = {
X8(I(DstReg | SrcImm64 | Mov, em_mov)),
/* 0xC0 - 0xC7 */
G(ByteOp | Src2ImmByte, group2), G(Src2ImmByte, group2),
- I(ImplicitOps | NearBranch | SrcImmU16, em_ret_near_imm),
- I(ImplicitOps | NearBranch, em_ret),
+ I(ImplicitOps | NearBranch | SrcImmU16 | IsBranch, em_ret_near_imm),
+ I(ImplicitOps | NearBranch | IsBranch, em_ret),
I(DstReg | SrcMemFAddr | ModRM | No64 | Src2ES, em_lseg),
I(DstReg | SrcMemFAddr | ModRM | No64 | Src2DS, em_lseg),
G(ByteOp, group11), G(0, group11),
/* 0xC8 - 0xCF */
- I(Stack | SrcImmU16 | Src2ImmByte, em_enter), I(Stack, em_leave),
- I(ImplicitOps | SrcImmU16, em_ret_far_imm),
- I(ImplicitOps, em_ret_far),
- D(ImplicitOps), DI(SrcImmByte, intn),
- D(ImplicitOps | No64), II(ImplicitOps, em_iret, iret),
+ I(Stack | SrcImmU16 | Src2ImmByte | IsBranch, em_enter),
+ I(Stack | IsBranch, em_leave),
+ I(ImplicitOps | SrcImmU16 | IsBranch, em_ret_far_imm),
+ I(ImplicitOps | IsBranch, em_ret_far),
+ D(ImplicitOps | IsBranch), DI(SrcImmByte | IsBranch, intn),
+ D(ImplicitOps | No64 | IsBranch),
+ II(ImplicitOps | IsBranch, em_iret, iret),
/* 0xD0 - 0xD7 */
G(Src2One | ByteOp, group2), G(Src2One, group2),
G(Src2CL | ByteOp, group2), G(Src2CL, group2),
@@ -4637,14 +4641,15 @@ static const struct opcode opcode_table[256] = {
/* 0xD8 - 0xDF */
N, E(0, &escape_d9), N, E(0, &escape_db), N, E(0, &escape_dd), N, N,
/* 0xE0 - 0xE7 */
- X3(I(SrcImmByte | NearBranch, em_loop)),
- I(SrcImmByte | NearBranch, em_jcxz),
+ X3(I(SrcImmByte | NearBranch | IsBranch, em_loop)),
+ I(SrcImmByte | NearBranch | IsBranch, em_jcxz),
I2bvIP(SrcImmUByte | DstAcc, em_in, in, check_perm_in),
I2bvIP(SrcAcc | DstImmUByte, em_out, out, check_perm_out),
/* 0xE8 - 0xEF */
- I(SrcImm | NearBranch, em_call), D(SrcImm | ImplicitOps | NearBranch),
- I(SrcImmFAddr | No64, em_jmp_far),
- D(SrcImmByte | ImplicitOps | NearBranch),
+ I(SrcImm | NearBranch | IsBranch, em_call),
+ D(SrcImm | ImplicitOps | NearBranch | IsBranch),
+ I(SrcImmFAddr | No64 | IsBranch, em_jmp_far),
+ D(SrcImmByte | ImplicitOps | NearBranch | IsBranch),
I2bvIP(SrcDX | DstAcc, em_in, in, check_perm_in),
I2bvIP(SrcAcc | DstDX, em_out, out, check_perm_out),
/* 0xF0 - 0xF7 */
@@ -4660,7 +4665,7 @@ static const struct opcode opcode_table[256] = {
static const struct opcode twobyte_table[256] = {
/* 0x00 - 0x0F */
G(0, group6), GD(0, &group7), N, N,
- N, I(ImplicitOps | EmulateOnUD, em_syscall),
+ N, I(ImplicitOps | EmulateOnUD | IsBranch, em_syscall),
II(ImplicitOps | Priv, em_clts, clts), N,
DI(ImplicitOps | Priv, invd), DI(ImplicitOps | Priv, wbinvd), N, N,
N, D(ImplicitOps | ModRM | SrcMem | NoAccess), N, N,
@@ -4691,8 +4696,8 @@ static const struct opcode twobyte_table[256] = {
IIP(ImplicitOps, em_rdtsc, rdtsc, check_rdtsc),
II(ImplicitOps | Priv, em_rdmsr, rdmsr),
IIP(ImplicitOps, em_rdpmc, rdpmc, check_rdpmc),
- I(ImplicitOps | EmulateOnUD, em_sysenter),
- I(ImplicitOps | Priv | EmulateOnUD, em_sysexit),
+ I(ImplicitOps | EmulateOnUD | IsBranch, em_sysenter),
+ I(ImplicitOps | Priv | EmulateOnUD | IsBranch, em_sysexit),
N, N,
N, N, N, N, N, N, N, N,
/* 0x40 - 0x4F */
@@ -4710,7 +4715,7 @@ static const struct opcode twobyte_table[256] = {
N, N, N, N,
N, N, N, GP(SrcReg | DstMem | ModRM | Mov, &pfx_0f_6f_0f_7f),
/* 0x80 - 0x8F */
- X16(D(SrcImm | NearBranch)),
+ X16(D(SrcImm | NearBranch | IsBranch)),
/* 0x90 - 0x9F */
X16(D(ByteOp | DstMem | SrcNone | ModRM| Mov)),
/* 0xA0 - 0xA7 */
@@ -5224,6 +5229,8 @@ int x86_decode_insn(struct x86_emulate_ctxt *ctxt, void *insn, int insn_len, int
ctxt->d |= opcode.flags;
}

+ ctxt->is_branch = opcode.flags & IsBranch;
+
/* Unrecognised? */
if (ctxt->d == 0)
return EMULATION_FAILED;
diff --git a/arch/x86/kvm/kvm_emulate.h b/arch/x86/kvm/kvm_emulate.h
index 68b420289d7e..39eded2426ff 100644
--- a/arch/x86/kvm/kvm_emulate.h
+++ b/arch/x86/kvm/kvm_emulate.h
@@ -369,6 +369,7 @@ struct x86_emulate_ctxt {
struct fetch_cache fetch;
struct read_cache io_read;
struct read_cache mem_read;
+ bool is_branch;
};

/* Repeat String Operation Prefix */
diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index 95f3823b3a9d..6e05d36aedd5 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -3504,10 +3504,13 @@ static int nested_vmx_run(struct kvm_vcpu *vcpu, bool launch)
if (evmptrld_status == EVMPTRLD_ERROR) {
kvm_queue_exception(vcpu, UD_VECTOR);
return 1;
- } else if (CC(evmptrld_status == EVMPTRLD_VMFAIL)) {
- return nested_vmx_failInvalid(vcpu);
}

+ kvm_pmu_trigger_event(vcpu, PERF_COUNT_HW_BRANCH_INSTRUCTIONS);
+
+ if (CC(evmptrld_status == EVMPTRLD_VMFAIL))
+ return nested_vmx_failInvalid(vcpu);
+
if (CC(!evmptr_is_valid(vmx->nested.hv_evmcs_vmptr) &&
vmx->nested.current_vmptr == INVALID_GPA))
return nested_vmx_failInvalid(vcpu);
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 83371be00771..c28226dcbe4e 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -8243,6 +8243,8 @@ int x86_emulate_instruction(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa,
if (!ctxt->have_exception ||
exception_type(ctxt->exception.vector) == EXCPT_TRAP) {
kvm_pmu_trigger_event(vcpu, PERF_COUNT_HW_INSTRUCTIONS);
+ if (ctxt->is_branch)
+ kvm_pmu_trigger_event(vcpu, PERF_COUNT_HW_BRANCH_INSTRUCTIONS);
kvm_rip_write(vcpu, ctxt->eip);
if (r && (ctxt->tf || (vcpu->guest_debug & KVM_GUESTDBG_SINGLESTEP)))
r = kvm_vcpu_do_singlestep(vcpu);
--
2.33.1

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