Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
x86/hyperv: Clean up hv_do_hypercall()
What used to be a simple few instructions has turned into a giant mess
(for x86_64). Not only does it use static_branch wrong, it mixes it
with dynamic branches for no apparent reason.
Notably it uses static_branch through an out-of-line function call,
which completely defeats the purpose, since instead of a simple
JMP/NOP site, you get a CALL+RET+TEST+Jcc sequence in return, which is
absolutely idiotic.
Add to that a dynamic test of hyperv_paravisor_present, something
which is set once and never changed.
Replace all this idiocy with a single direct function call to the
right hypercall variant.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Michael Kelley <mhklinux@outlook.com>
Tested-by: Michael Kelley <mhklinux@outlook.com>
Acked-by: Sean Christopherson <seanjc@google.com>
Link: https://lkml.kernel.org/r/20250714103440.897136093@infradead.org
+89
-102
+20
arch/x86/hyperv/hv_init.c
+20
arch/x86/hyperv/hv_init.c
···
37
37
#include <linux/export.h>
38
38
39
39
void *hv_hypercall_pg;
40
+
41
+
#ifdef CONFIG_X86_64
42
+
u64 hv_std_hypercall(u64 control, u64 param1, u64 param2)
43
+
{
44
+
u64 hv_status;
45
+
46
+
if (!hv_hypercall_pg)
47
+
return U64_MAX;
48
+
49
+
register u64 __r8 asm("r8") = param2;
50
+
asm volatile (CALL_NOSPEC
51
+
: "=a" (hv_status), ASM_CALL_CONSTRAINT,
52
+
"+c" (control), "+d" (param1), "+r" (__r8)
53
+
: THUNK_TARGET(hv_hypercall_pg)
54
+
: "cc", "memory", "r9", "r10", "r11");
55
+
56
+
return hv_status;
57
+
}
58
+
#else
40
59
EXPORT_SYMBOL_GPL(hv_hypercall_pg);
60
+
#endif
41
61
42
62
union hv_ghcb * __percpu *hv_ghcb_pg;
43
63
+15
arch/x86/hyperv/ivm.c
+15
arch/x86/hyperv/ivm.c
···
385
385
return ret;
386
386
}
387
387
388
+
u64 hv_snp_hypercall(u64 control, u64 param1, u64 param2)
389
+
{
390
+
u64 hv_status;
391
+
392
+
register u64 __r8 asm("r8") = param2;
393
+
asm volatile("vmmcall"
394
+
: "=a" (hv_status), ASM_CALL_CONSTRAINT,
395
+
"+c" (control), "+d" (param1), "+r" (__r8)
396
+
: : "cc", "memory", "r9", "r10", "r11");
397
+
398
+
return hv_status;
399
+
}
400
+
388
401
#else
389
402
static inline void hv_ghcb_msr_write(u64 msr, u64 value) {}
390
403
static inline void hv_ghcb_msr_read(u64 msr, u64 *value) {}
404
+
u64 hv_snp_hypercall(u64 control, u64 param1, u64 param2) { return U64_MAX; }
391
405
#endif /* CONFIG_AMD_MEM_ENCRYPT */
392
406
393
407
#ifdef CONFIG_INTEL_TDX_GUEST
···
451
437
#else
452
438
static inline void hv_tdx_msr_write(u64 msr, u64 value) {}
453
439
static inline void hv_tdx_msr_read(u64 msr, u64 *value) {}
440
+
u64 hv_tdx_hypercall(u64 control, u64 param1, u64 param2) { return U64_MAX; }
454
441
#endif /* CONFIG_INTEL_TDX_GUEST */
455
442
456
443
#if defined(CONFIG_AMD_MEM_ENCRYPT) || defined(CONFIG_INTEL_TDX_GUEST)
+41
-96
arch/x86/include/asm/mshyperv.h
+41
-96
arch/x86/include/asm/mshyperv.h
···
6
6
#include <linux/nmi.h>
7
7
#include <linux/msi.h>
8
8
#include <linux/io.h>
9
+
#include <linux/static_call.h>
9
10
#include <asm/nospec-branch.h>
10
11
#include <asm/paravirt.h>
11
12
#include <asm/msr.h>
···
40
39
return 0;
41
40
}
42
41
43
-
#if IS_ENABLED(CONFIG_HYPERV)
44
-
extern bool hyperv_paravisor_present;
42
+
extern u64 hv_tdx_hypercall(u64 control, u64 param1, u64 param2);
43
+
extern u64 hv_snp_hypercall(u64 control, u64 param1, u64 param2);
44
+
extern u64 hv_std_hypercall(u64 control, u64 param1, u64 param2);
45
45
46
+
#if IS_ENABLED(CONFIG_HYPERV)
46
47
extern void *hv_hypercall_pg;
47
48
48
49
extern union hv_ghcb * __percpu *hv_ghcb_pg;
49
50
50
51
bool hv_isolation_type_snp(void);
51
52
bool hv_isolation_type_tdx(void);
52
-
u64 hv_tdx_hypercall(u64 control, u64 param1, u64 param2);
53
+
54
+
#ifdef CONFIG_X86_64
55
+
DECLARE_STATIC_CALL(hv_hypercall, hv_std_hypercall);
56
+
#endif
53
57
54
58
/*
55
59
* DEFAULT INIT GPAT and SEGMENT LIMIT value in struct VMSA
···
71
65
{
72
66
u64 input_address = input ? virt_to_phys(input) : 0;
73
67
u64 output_address = output ? virt_to_phys(output) : 0;
74
-
u64 hv_status;
75
68
76
69
#ifdef CONFIG_X86_64
77
-
if (hv_isolation_type_tdx() && !hyperv_paravisor_present)
78
-
return hv_tdx_hypercall(control, input_address, output_address);
79
-
80
-
if (hv_isolation_type_snp() && !hyperv_paravisor_present) {
81
-
__asm__ __volatile__("mov %[output_address], %%r8\n"
82
-
"vmmcall"
83
-
: "=a" (hv_status), ASM_CALL_CONSTRAINT,
84
-
"+c" (control), "+d" (input_address)
85
-
: [output_address] "r" (output_address)
86
-
: "cc", "memory", "r8", "r9", "r10", "r11");
87
-
return hv_status;
88
-
}
89
-
90
-
if (!hv_hypercall_pg)
91
-
return U64_MAX;
92
-
93
-
__asm__ __volatile__("mov %[output_address], %%r8\n"
94
-
CALL_NOSPEC
95
-
: "=a" (hv_status), ASM_CALL_CONSTRAINT,
96
-
"+c" (control), "+d" (input_address)
97
-
: [output_address] "r" (output_address),
98
-
THUNK_TARGET(hv_hypercall_pg)
99
-
: "cc", "memory", "r8", "r9", "r10", "r11");
70
+
return static_call_mod(hv_hypercall)(control, input_address, output_address);
100
71
#else
101
72
u32 input_address_hi = upper_32_bits(input_address);
102
73
u32 input_address_lo = lower_32_bits(input_address);
103
74
u32 output_address_hi = upper_32_bits(output_address);
104
75
u32 output_address_lo = lower_32_bits(output_address);
76
+
u64 hv_status;
105
77
106
78
if (!hv_hypercall_pg)
107
79
return U64_MAX;
···
92
108
"D"(output_address_hi), "S"(output_address_lo),
93
109
THUNK_TARGET(hv_hypercall_pg)
94
110
: "cc", "memory");
95
-
#endif /* !x86_64 */
96
111
return hv_status;
112
+
#endif /* !x86_64 */
97
113
}
98
114
99
115
/* Fast hypercall with 8 bytes of input and no output */
100
116
static inline u64 _hv_do_fast_hypercall8(u64 control, u64 input1)
101
117
{
118
+
#ifdef CONFIG_X86_64
119
+
return static_call_mod(hv_hypercall)(control, input1, 0);
120
+
#else
121
+
u32 input1_hi = upper_32_bits(input1);
122
+
u32 input1_lo = lower_32_bits(input1);
102
123
u64 hv_status;
103
124
104
-
#ifdef CONFIG_X86_64
105
-
if (hv_isolation_type_tdx() && !hyperv_paravisor_present)
106
-
return hv_tdx_hypercall(control, input1, 0);
107
-
108
-
if (hv_isolation_type_snp() && !hyperv_paravisor_present) {
109
-
__asm__ __volatile__(
110
-
"vmmcall"
111
-
: "=a" (hv_status), ASM_CALL_CONSTRAINT,
112
-
"+c" (control), "+d" (input1)
113
-
:: "cc", "r8", "r9", "r10", "r11");
114
-
} else {
115
-
__asm__ __volatile__(CALL_NOSPEC
116
-
: "=a" (hv_status), ASM_CALL_CONSTRAINT,
117
-
"+c" (control), "+d" (input1)
118
-
: THUNK_TARGET(hv_hypercall_pg)
119
-
: "cc", "r8", "r9", "r10", "r11");
120
-
}
121
-
#else
122
-
{
123
-
u32 input1_hi = upper_32_bits(input1);
124
-
u32 input1_lo = lower_32_bits(input1);
125
-
126
-
__asm__ __volatile__ (CALL_NOSPEC
127
-
: "=A"(hv_status),
128
-
"+c"(input1_lo),
129
-
ASM_CALL_CONSTRAINT
130
-
: "A" (control),
131
-
"b" (input1_hi),
132
-
THUNK_TARGET(hv_hypercall_pg)
133
-
: "cc", "edi", "esi");
134
-
}
135
-
#endif
125
+
__asm__ __volatile__ (CALL_NOSPEC
126
+
: "=A"(hv_status),
127
+
"+c"(input1_lo),
128
+
ASM_CALL_CONSTRAINT
129
+
: "A" (control),
130
+
"b" (input1_hi),
131
+
THUNK_TARGET(hv_hypercall_pg)
132
+
: "cc", "edi", "esi");
136
133
return hv_status;
134
+
#endif
137
135
}
138
136
139
137
static inline u64 hv_do_fast_hypercall8(u16 code, u64 input1)
···
128
162
/* Fast hypercall with 16 bytes of input */
129
163
static inline u64 _hv_do_fast_hypercall16(u64 control, u64 input1, u64 input2)
130
164
{
165
+
#ifdef CONFIG_X86_64
166
+
return static_call_mod(hv_hypercall)(control, input1, input2);
167
+
#else
168
+
u32 input1_hi = upper_32_bits(input1);
169
+
u32 input1_lo = lower_32_bits(input1);
170
+
u32 input2_hi = upper_32_bits(input2);
171
+
u32 input2_lo = lower_32_bits(input2);
131
172
u64 hv_status;
132
173
133
-
#ifdef CONFIG_X86_64
134
-
if (hv_isolation_type_tdx() && !hyperv_paravisor_present)
135
-
return hv_tdx_hypercall(control, input1, input2);
136
-
137
-
if (hv_isolation_type_snp() && !hyperv_paravisor_present) {
138
-
__asm__ __volatile__("mov %[input2], %%r8\n"
139
-
"vmmcall"
140
-
: "=a" (hv_status), ASM_CALL_CONSTRAINT,
141
-
"+c" (control), "+d" (input1)
142
-
: [input2] "r" (input2)
143
-
: "cc", "r8", "r9", "r10", "r11");
144
-
} else {
145
-
__asm__ __volatile__("mov %[input2], %%r8\n"
146
-
CALL_NOSPEC
147
-
: "=a" (hv_status), ASM_CALL_CONSTRAINT,
148
-
"+c" (control), "+d" (input1)
149
-
: [input2] "r" (input2),
150
-
THUNK_TARGET(hv_hypercall_pg)
151
-
: "cc", "r8", "r9", "r10", "r11");
152
-
}
153
-
#else
154
-
{
155
-
u32 input1_hi = upper_32_bits(input1);
156
-
u32 input1_lo = lower_32_bits(input1);
157
-
u32 input2_hi = upper_32_bits(input2);
158
-
u32 input2_lo = lower_32_bits(input2);
159
-
160
-
__asm__ __volatile__ (CALL_NOSPEC
161
-
: "=A"(hv_status),
162
-
"+c"(input1_lo), ASM_CALL_CONSTRAINT
163
-
: "A" (control), "b" (input1_hi),
164
-
"D"(input2_hi), "S"(input2_lo),
165
-
THUNK_TARGET(hv_hypercall_pg)
166
-
: "cc");
167
-
}
168
-
#endif
174
+
__asm__ __volatile__ (CALL_NOSPEC
175
+
: "=A"(hv_status),
176
+
"+c"(input1_lo), ASM_CALL_CONSTRAINT
177
+
: "A" (control), "b" (input1_hi),
178
+
"D"(input2_hi), "S"(input2_lo),
179
+
THUNK_TARGET(hv_hypercall_pg)
180
+
: "cc");
169
181
return hv_status;
182
+
#endif
170
183
}
171
184
172
185
static inline u64 hv_do_fast_hypercall16(u16 code, u64 input1, u64 input2)
+13
-6
arch/x86/kernel/cpu/mshyperv.c
+13
-6
arch/x86/kernel/cpu/mshyperv.c
···
38
38
bool hv_nested;
39
39
struct ms_hyperv_info ms_hyperv;
40
40
41
-
/* Used in modules via hv_do_hypercall(): see arch/x86/include/asm/mshyperv.h */
42
-
bool hyperv_paravisor_present __ro_after_init;
43
-
EXPORT_SYMBOL_GPL(hyperv_paravisor_present);
44
-
45
41
#if IS_ENABLED(CONFIG_HYPERV)
46
42
static inline unsigned int hv_get_nested_msr(unsigned int reg)
47
43
{
···
284
288
old_restore_sched_clock_state = x86_platform.restore_sched_clock_state;
285
289
x86_platform.restore_sched_clock_state = hv_restore_sched_clock_state;
286
290
}
291
+
292
+
#ifdef CONFIG_X86_64
293
+
DEFINE_STATIC_CALL(hv_hypercall, hv_std_hypercall);
294
+
EXPORT_STATIC_CALL_TRAMP_GPL(hv_hypercall);
295
+
#define hypercall_update(hc) static_call_update(hv_hypercall, hc)
296
+
#endif
287
297
#endif /* CONFIG_HYPERV */
298
+
299
+
#ifndef hypercall_update
300
+
#define hypercall_update(hc) (void)hc
301
+
#endif
288
302
289
303
static uint32_t __init ms_hyperv_platform(void)
290
304
{
···
490
484
ms_hyperv.shared_gpa_boundary =
491
485
BIT_ULL(ms_hyperv.shared_gpa_boundary_bits);
492
486
493
-
hyperv_paravisor_present = !!ms_hyperv.paravisor_present;
494
-
495
487
pr_info("Hyper-V: Isolation Config: Group A 0x%x, Group B 0x%x\n",
496
488
ms_hyperv.isolation_config_a, ms_hyperv.isolation_config_b);
497
489
498
490
499
491
if (hv_get_isolation_type() == HV_ISOLATION_TYPE_SNP) {
500
492
static_branch_enable(&isolation_type_snp);
493
+
if (!ms_hyperv.paravisor_present)
494
+
hypercall_update(hv_snp_hypercall);
501
495
} else if (hv_get_isolation_type() == HV_ISOLATION_TYPE_TDX) {
502
496
static_branch_enable(&isolation_type_tdx);
503
497
···
505
499
ms_hyperv.hints &= ~HV_X64_APIC_ACCESS_RECOMMENDED;
506
500
507
501
if (!ms_hyperv.paravisor_present) {
502
+
hypercall_update(hv_tdx_hypercall);
508
503
/*
509
504
* Mark the Hyper-V TSC page feature as disabled
510
505
* in a TDX VM without paravisor so that the