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target/arm: Check supported KVM features globally (not per vCPU)
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Since commit d70c996, when enabling the PMU we get:

  $ qemu-system-aarch64 -cpu host,pmu=on -M virt,accel=kvm,gic-version=3
  Segmentation fault (core dumped)

  Thread 1 "qemu-system-aar" received signal SIGSEGV, Segmentation fault.
  0x0000aaaaaae356d0 in kvm_ioctl (s=0x0, type=44547) at accel/kvm/kvm-all.c:2588
  2588        ret = ioctl(s->fd, type, arg);
  (gdb) bt
  #0  0x0000aaaaaae356d0 in kvm_ioctl (s=0x0, type=44547) at accel/kvm/kvm-all.c:2588
  #1  0x0000aaaaaae31568 in kvm_check_extension (s=0x0, extension=126) at accel/kvm/kvm-all.c:916
  #2  0x0000aaaaaafce254 in kvm_arm_pmu_supported (cpu=0xaaaaac214ab0) at target/arm/kvm.c:213
  #3  0x0000aaaaaafc0f94 in arm_set_pmu (obj=0xaaaaac214ab0, value=true, errp=0xffffffffe438) at target/arm/cpu.c:1111
  #4  0x0000aaaaab5533ac in property_set_bool (obj=0xaaaaac214ab0, v=0xaaaaac223a80, name=0xaaaaac11a970 "pmu", opaque=0xaaaaac222730, errp=0xffffffffe438) at qom/object.c:2170
  #5  0x0000aaaaab5512f0 in object_property_set (obj=0xaaaaac214ab0, v=0xaaaaac223a80, name=0xaaaaac11a970 "pmu", errp=0xffffffffe438) at qom/object.c:1328
  #6  0x0000aaaaab551e10 in object_property_parse (obj=0xaaaaac214ab0, string=0xaaaaac11b4c0 "on", name=0xaaaaac11a970 "pmu", errp=0xffffffffe438) at qom/object.c:1561
  #7  0x0000aaaaab54ee8c in object_apply_global_props (obj=0xaaaaac214ab0, props=0xaaaaac018e20, errp=0xaaaaabd6fd88 <error_fatal>) at qom/object.c:407
  #8  0x0000aaaaab1dd5a4 in qdev_prop_set_globals (dev=0xaaaaac214ab0) at hw/core/qdev-properties.c:1218
  #9  0x0000aaaaab1d9fac in device_post_init (obj=0xaaaaac214ab0) at hw/core/qdev.c:1050
  ...
  #15 0x0000aaaaab54f310 in object_initialize_with_type (obj=0xaaaaac214ab0, size=52208, type=0xaaaaabe237f0) at qom/object.c:512
  #16 0x0000aaaaab54fa24 in object_new_with_type (type=0xaaaaabe237f0) at qom/object.c:687
  #17 0x0000aaaaab54fa80 in object_new (typename=0xaaaaabe23970 "host-arm-cpu") at qom/object.c:702
  #18 0x0000aaaaaaf04a74 in machvirt_init (machine=0xaaaaac0a8550) at hw/arm/virt.c:1770
  #19 0x0000aaaaab1e8720 in machine_run_board_init (machine=0xaaaaac0a8550) at hw/core/machine.c:1138
  #20 0x0000aaaaaaf95394 in qemu_init (argc=5, argv=0xffffffffea58, envp=0xffffffffea88) at softmmu/vl.c:4348
  #21 0x0000aaaaaada3f74 in main (argc=<optimized out>, argv=<optimized out>, envp=<optimized out>) at softmmu/main.c:48

This is because in frame #2, cpu->kvm_state is still NULL
(the vCPU is not yet realized).

KVM has a hard requirement of all cores supporting the same
feature set. We only need to check if the accelerator supports
a feature, not each vCPU individually.

Fix by removing the 'CPUState *cpu' argument from the
kvm_arm_<FEATURE>_supported() functions.

Fixes: d70c996 ('Use CPUState::kvm_state in kvm_arm_pmu_supported')
Reported-by: Haibo Xu <[email protected]>
Reviewed-by: Andrew Jones <[email protected]>
Acked-by: Paolo Bonzini <[email protected]>
Signed-off-by: Philippe Mathieu-Daudé <[email protected]>
Suggested-by: Paolo Bonzini <[email protected]>
Signed-off-by: Philippe Mathieu-Daudé <[email protected]>
Signed-off-by: Peter Maydell <[email protected]>
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@philmd @pm215
philmd authored and pm215 committed Jun 23, 2020
1 parent 2e34818 commit 7d20e68
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Showing 5 changed files with 22 additions and 29 deletions.
2 changes: 1 addition & 1 deletion target/arm/cpu.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1108,7 +1108,7 @@ static void arm_set_pmu(Object *obj, bool value, Error **errp)
ARMCPU *cpu = ARM_CPU(obj);

if (value) {
if (kvm_enabled() && !kvm_arm_pmu_supported(CPU(cpu))) {
if (kvm_enabled() && !kvm_arm_pmu_supported()) {
error_setg(errp, "'pmu' feature not supported by KVM on this host");
return;
}
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10 changes: 5 additions & 5 deletions target/arm/cpu64.c
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Original file line number Diff line number Diff line change
Expand Up @@ -266,7 +266,7 @@ void arm_cpu_sve_finalize(ARMCPU *cpu, Error **errp)

/* Collect the set of vector lengths supported by KVM. */
bitmap_zero(kvm_supported, ARM_MAX_VQ);
if (kvm_enabled() && kvm_arm_sve_supported(CPU(cpu))) {
if (kvm_enabled() && kvm_arm_sve_supported()) {
kvm_arm_sve_get_vls(CPU(cpu), kvm_supported);
} else if (kvm_enabled()) {
assert(!cpu_isar_feature(aa64_sve, cpu));
Expand Down Expand Up @@ -473,7 +473,7 @@ static void cpu_max_set_sve_max_vq(Object *obj, Visitor *v, const char *name,
return;
}

if (kvm_enabled() && !kvm_arm_sve_supported(CPU(cpu))) {
if (kvm_enabled() && !kvm_arm_sve_supported()) {
error_setg(errp, "cannot set sve-max-vq");
error_append_hint(errp, "SVE not supported by KVM on this host\n");
return;
Expand Down Expand Up @@ -519,7 +519,7 @@ static void cpu_arm_set_sve_vq(Object *obj, Visitor *v, const char *name,
return;
}

if (value && kvm_enabled() && !kvm_arm_sve_supported(CPU(cpu))) {
if (value && kvm_enabled() && !kvm_arm_sve_supported()) {
error_setg(errp, "cannot enable %s", name);
error_append_hint(errp, "SVE not supported by KVM on this host\n");
return;
Expand Down Expand Up @@ -556,7 +556,7 @@ static void cpu_arm_set_sve(Object *obj, Visitor *v, const char *name,
return;
}

if (value && kvm_enabled() && !kvm_arm_sve_supported(CPU(cpu))) {
if (value && kvm_enabled() && !kvm_arm_sve_supported()) {
error_setg(errp, "'sve' feature not supported by KVM on this host");
return;
}
Expand Down Expand Up @@ -751,7 +751,7 @@ static void aarch64_cpu_set_aarch64(Object *obj, bool value, Error **errp)
* uniform execution state like do_interrupt.
*/
if (value == false) {
if (!kvm_enabled() || !kvm_arm_aarch32_supported(CPU(cpu))) {
if (!kvm_enabled() || !kvm_arm_aarch32_supported()) {
error_setg(errp, "'aarch64' feature cannot be disabled "
"unless KVM is enabled and 32-bit EL1 "
"is supported");
Expand Down
4 changes: 2 additions & 2 deletions target/arm/kvm.c
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Original file line number Diff line number Diff line change
Expand Up @@ -208,9 +208,9 @@ void kvm_arm_add_vcpu_properties(Object *obj)
}
}

bool kvm_arm_pmu_supported(CPUState *cpu)
bool kvm_arm_pmu_supported(void)
{
return kvm_check_extension(cpu->kvm_state, KVM_CAP_ARM_PMU_V3);
return kvm_check_extension(kvm_state, KVM_CAP_ARM_PMU_V3);
}

int kvm_arm_get_max_vm_ipa_size(MachineState *ms)
Expand Down
14 changes: 5 additions & 9 deletions target/arm/kvm64.c
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Original file line number Diff line number Diff line change
Expand Up @@ -652,18 +652,14 @@ bool kvm_arm_get_host_cpu_features(ARMHostCPUFeatures *ahcf)
return true;
}

bool kvm_arm_aarch32_supported(CPUState *cpu)
bool kvm_arm_aarch32_supported(void)
{
KVMState *s = KVM_STATE(current_accel());

return kvm_check_extension(s, KVM_CAP_ARM_EL1_32BIT);
return kvm_check_extension(kvm_state, KVM_CAP_ARM_EL1_32BIT);
}

bool kvm_arm_sve_supported(CPUState *cpu)
bool kvm_arm_sve_supported(void)
{
KVMState *s = KVM_STATE(current_accel());

return kvm_check_extension(s, KVM_CAP_ARM_SVE);
return kvm_check_extension(kvm_state, KVM_CAP_ARM_SVE);
}

QEMU_BUILD_BUG_ON(KVM_ARM64_SVE_VQ_MIN != 1);
Expand Down Expand Up @@ -798,7 +794,7 @@ int kvm_arch_init_vcpu(CPUState *cs)
env->features &= ~(1ULL << ARM_FEATURE_PMU);
}
if (cpu_isar_feature(aa64_sve, cpu)) {
assert(kvm_arm_sve_supported(cs));
assert(kvm_arm_sve_supported());
cpu->kvm_init_features[0] |= 1 << KVM_ARM_VCPU_SVE;
}

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21 changes: 9 additions & 12 deletions target/arm/kvm_arm.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -269,29 +269,26 @@ void kvm_arm_add_vcpu_properties(Object *obj);

/**
* kvm_arm_aarch32_supported:
* @cs: CPUState
*
* Returns: true if the KVM VCPU can enable AArch32 mode
* Returns: true if KVM can enable AArch32 mode
* and false otherwise.
*/
bool kvm_arm_aarch32_supported(CPUState *cs);
bool kvm_arm_aarch32_supported(void);

/**
* kvm_arm_pmu_supported:
* @cs: CPUState
*
* Returns: true if the KVM VCPU can enable its PMU
* Returns: true if KVM can enable the PMU
* and false otherwise.
*/
bool kvm_arm_pmu_supported(CPUState *cs);
bool kvm_arm_pmu_supported(void);

/**
* kvm_arm_sve_supported:
* @cs: CPUState
*
* Returns true if the KVM VCPU can enable SVE and false otherwise.
* Returns true if KVM can enable SVE and false otherwise.
*/
bool kvm_arm_sve_supported(CPUState *cs);
bool kvm_arm_sve_supported(void);

/**
* kvm_arm_get_max_vm_ipa_size:
Expand Down Expand Up @@ -359,17 +356,17 @@ static inline void kvm_arm_set_cpu_features_from_host(ARMCPU *cpu)

static inline void kvm_arm_add_vcpu_properties(Object *obj) {}

static inline bool kvm_arm_aarch32_supported(CPUState *cs)
static inline bool kvm_arm_aarch32_supported(void)
{
return false;
}

static inline bool kvm_arm_pmu_supported(CPUState *cs)
static inline bool kvm_arm_pmu_supported(void)
{
return false;
}

static inline bool kvm_arm_sve_supported(CPUState *cs)
static inline bool kvm_arm_sve_supported(void)
{
return false;
}
Expand Down

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