From: Wanpeng Li <[email protected]>
------------[ cut here ]------------
Bad FPU state detected at kvm_put_guest_fpu+0xd8/0x2d0 [kvm], reinitializing FPU registers.
WARNING: CPU: 1 PID: 4594 at arch/x86/mm/extable.c:103 ex_handler_fprestore+0x88/0x90
CPU: 1 PID: 4594 Comm: qemu-system-x86 Tainted: G B OE 4.15.0-rc2+ #10
RIP: 0010:ex_handler_fprestore+0x88/0x90
Call Trace:
fixup_exception+0x4e/0x60
do_general_protection+0xff/0x270
general_protection+0x22/0x30
RIP: 0010:kvm_put_guest_fpu+0xd8/0x2d0 [kvm]
RSP: 0018:ffff8803d5627810 EFLAGS: 00010246
kvm_vcpu_reset+0x3b4/0x3c0 [kvm]
kvm_apic_accept_events+0x1c0/0x240 [kvm]
kvm_arch_vcpu_ioctl_run+0x1658/0x2fb0 [kvm]
kvm_vcpu_ioctl+0x479/0x880 [kvm]
do_vfs_ioctl+0x142/0x9a0
SyS_ioctl+0x74/0x80
do_syscall_64+0x15f/0x600
This can be reproduced by running any testcase in kvm-unit-tests since
the qemu userspace FPU context is not initialized, which results in the
init path from kvm_apic_accept_events() will load/put qemu userspace
FPU context w/o initialized. In addition, w/o this splatting we still
should initialize vcpu->arch.user_fpu instead of current->thread.fpu.
This patch fixes it by initializing qemu user FPU context if it is
uninitialized before KVM_RUN.
Cc: Paolo Bonzini <[email protected]>
Cc: Radim Krčmář <[email protected]>
Cc: Rik van Riel <[email protected]>
Cc: [email protected]
Fixes: f775b13eedee (x86,kvm: move qemu/guest FPU switching out to vcpu_run)
Signed-off-by: Wanpeng Li <[email protected]>
---
arch/x86/kvm/x86.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index a92b22f..063a643 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -7273,10 +7273,13 @@ static int complete_emulated_mmio(struct kvm_vcpu *vcpu)
int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
{
- struct fpu *fpu = ¤t->thread.fpu;
+ struct fpu *fpu = &vcpu->arch.user_fpu;
int r;
- fpu__initialize(fpu);
+ if (!fpu->initialized) {
+ fpstate_init(&fpu->state);
+ fpu->initialized = 1;
+ }
kvm_sigset_activate(vcpu);
--
2.7.4
On 10.12.2017 22:44, Wanpeng Li wrote:
> From: Wanpeng Li <[email protected]>
>
> ------------[ cut here ]------------
> Bad FPU state detected at kvm_put_guest_fpu+0xd8/0x2d0 [kvm], reinitializing FPU registers.
> WARNING: CPU: 1 PID: 4594 at arch/x86/mm/extable.c:103 ex_handler_fprestore+0x88/0x90
> CPU: 1 PID: 4594 Comm: qemu-system-x86 Tainted: G B OE 4.15.0-rc2+ #10
> RIP: 0010:ex_handler_fprestore+0x88/0x90
> Call Trace:
> fixup_exception+0x4e/0x60
> do_general_protection+0xff/0x270
> general_protection+0x22/0x30
> RIP: 0010:kvm_put_guest_fpu+0xd8/0x2d0 [kvm]
> RSP: 0018:ffff8803d5627810 EFLAGS: 00010246
> kvm_vcpu_reset+0x3b4/0x3c0 [kvm]
> kvm_apic_accept_events+0x1c0/0x240 [kvm]
> kvm_arch_vcpu_ioctl_run+0x1658/0x2fb0 [kvm]
> kvm_vcpu_ioctl+0x479/0x880 [kvm]
> do_vfs_ioctl+0x142/0x9a0
> SyS_ioctl+0x74/0x80
> do_syscall_64+0x15f/0x600
>
> This can be reproduced by running any testcase in kvm-unit-tests since
> the qemu userspace FPU context is not initialized, which results in the
> init path from kvm_apic_accept_events() will load/put qemu userspace
> FPU context w/o initialized. In addition, w/o this splatting we still
> should initialize vcpu->arch.user_fpu instead of current->thread.fpu.
> This patch fixes it by initializing qemu user FPU context if it is
> uninitialized before KVM_RUN.
>
> Cc: Paolo Bonzini <[email protected]>
> Cc: Radim Krčmář <[email protected]>
> Cc: Rik van Riel <[email protected]>
> Cc: [email protected]
> Fixes: f775b13eedee (x86,kvm: move qemu/guest FPU switching out to vcpu_run)
> Signed-off-by: Wanpeng Li <[email protected]>
> ---
> arch/x86/kvm/x86.c | 7 +++++--
> 1 file changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index a92b22f..063a643 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -7273,10 +7273,13 @@ static int complete_emulated_mmio(struct kvm_vcpu *vcpu)
>
> int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
> {
> - struct fpu *fpu = ¤t->thread.fpu;
> + struct fpu *fpu = &vcpu->arch.user_fpu;
> int r;
>
> - fpu__initialize(fpu);
> + if (!fpu->initialized) {
> + fpstate_init(&fpu->state);
> + fpu->initialized = 1;
> + }
Is there a chance of keeping using fpu__initialize() ? Duplicating the
code is ugly.
E.g. can't we simply initialize that in kvm_load_guest_fpu?
>
> kvm_sigset_activate(vcpu);
>
>
--
Thanks,
David / dhildenb
2017-12-12 4:48 GMT+08:00 David Hildenbrand <[email protected]>:
> On 10.12.2017 22:44, Wanpeng Li wrote:
>> From: Wanpeng Li <[email protected]>
>>
>> ------------[ cut here ]------------
>> Bad FPU state detected at kvm_put_guest_fpu+0xd8/0x2d0 [kvm], reinitializing FPU registers.
>> WARNING: CPU: 1 PID: 4594 at arch/x86/mm/extable.c:103 ex_handler_fprestore+0x88/0x90
>> CPU: 1 PID: 4594 Comm: qemu-system-x86 Tainted: G B OE 4.15.0-rc2+ #10
>> RIP: 0010:ex_handler_fprestore+0x88/0x90
>> Call Trace:
>> fixup_exception+0x4e/0x60
>> do_general_protection+0xff/0x270
>> general_protection+0x22/0x30
>> RIP: 0010:kvm_put_guest_fpu+0xd8/0x2d0 [kvm]
>> RSP: 0018:ffff8803d5627810 EFLAGS: 00010246
>> kvm_vcpu_reset+0x3b4/0x3c0 [kvm]
>> kvm_apic_accept_events+0x1c0/0x240 [kvm]
>> kvm_arch_vcpu_ioctl_run+0x1658/0x2fb0 [kvm]
>> kvm_vcpu_ioctl+0x479/0x880 [kvm]
>> do_vfs_ioctl+0x142/0x9a0
>> SyS_ioctl+0x74/0x80
>> do_syscall_64+0x15f/0x600
>>
>> This can be reproduced by running any testcase in kvm-unit-tests since
>> the qemu userspace FPU context is not initialized, which results in the
>> init path from kvm_apic_accept_events() will load/put qemu userspace
>> FPU context w/o initialized. In addition, w/o this splatting we still
>> should initialize vcpu->arch.user_fpu instead of current->thread.fpu.
>> This patch fixes it by initializing qemu user FPU context if it is
>> uninitialized before KVM_RUN.
>>
>> Cc: Paolo Bonzini <[email protected]>
>> Cc: Radim Krčmář <[email protected]>
>> Cc: Rik van Riel <[email protected]>
>> Cc: [email protected]
>> Fixes: f775b13eedee (x86,kvm: move qemu/guest FPU switching out to vcpu_run)
>> Signed-off-by: Wanpeng Li <[email protected]>
>> ---
>> arch/x86/kvm/x86.c | 7 +++++--
>> 1 file changed, 5 insertions(+), 2 deletions(-)
>>
>> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
>> index a92b22f..063a643 100644
>> --- a/arch/x86/kvm/x86.c
>> +++ b/arch/x86/kvm/x86.c
>> @@ -7273,10 +7273,13 @@ static int complete_emulated_mmio(struct kvm_vcpu *vcpu)
>>
>> int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
>> {
>> - struct fpu *fpu = ¤t->thread.fpu;
>> + struct fpu *fpu = &vcpu->arch.user_fpu;
>> int r;
>>
>> - fpu__initialize(fpu);
>> + if (!fpu->initialized) {
>> + fpstate_init(&fpu->state);
>> + fpu->initialized = 1;
>> + }
>
> Is there a chance of keeping using fpu__initialize() ? Duplicating the
> code is ugly.
There is a warning in fpu__initialize() which results in just
current->thread.fpu can take advantage of.
>
> E.g. can't we simply initialize that in kvm_load_guest_fpu?
We still miss to initialize qemu user FPU context for the above calltrace.
Regards,
Wanpeng Li
On Tue, Dec 12, 2017 at 05:51:26AM +0800, Wanpeng Li wrote:
> 2017-12-12 4:48 GMT+08:00 David Hildenbrand <[email protected]>:
> > On 10.12.2017 22:44, Wanpeng Li wrote:
> >> From: Wanpeng Li <[email protected]>
> >>
> >> ------------[ cut here ]------------
> >> Bad FPU state detected at kvm_put_guest_fpu+0xd8/0x2d0 [kvm], reinitializing FPU registers.
> >> WARNING: CPU: 1 PID: 4594 at arch/x86/mm/extable.c:103 ex_handler_fprestore+0x88/0x90
> >> CPU: 1 PID: 4594 Comm: qemu-system-x86 Tainted: G B OE 4.15.0-rc2+ #10
> >> RIP: 0010:ex_handler_fprestore+0x88/0x90
> >> Call Trace:
> >> fixup_exception+0x4e/0x60
> >> do_general_protection+0xff/0x270
> >> general_protection+0x22/0x30
> >> RIP: 0010:kvm_put_guest_fpu+0xd8/0x2d0 [kvm]
> >> RSP: 0018:ffff8803d5627810 EFLAGS: 00010246
> >> kvm_vcpu_reset+0x3b4/0x3c0 [kvm]
> >> kvm_apic_accept_events+0x1c0/0x240 [kvm]
> >> kvm_arch_vcpu_ioctl_run+0x1658/0x2fb0 [kvm]
> >> kvm_vcpu_ioctl+0x479/0x880 [kvm]
> >> do_vfs_ioctl+0x142/0x9a0
> >> SyS_ioctl+0x74/0x80
> >> do_syscall_64+0x15f/0x600
> >>
> >> This can be reproduced by running any testcase in kvm-unit-tests since
> >> the qemu userspace FPU context is not initialized, which results in the
> >> init path from kvm_apic_accept_events() will load/put qemu userspace
> >> FPU context w/o initialized. In addition, w/o this splatting we still
> >> should initialize vcpu->arch.user_fpu instead of current->thread.fpu.
> >> This patch fixes it by initializing qemu user FPU context if it is
> >> uninitialized before KVM_RUN.
> >>
> >> Cc: Paolo Bonzini <[email protected]>
> >> Cc: Radim Krčmář <[email protected]>
> >> Cc: Rik van Riel <[email protected]>
> >> Cc: [email protected]
> >> Fixes: f775b13eedee (x86,kvm: move qemu/guest FPU switching out to vcpu_run)
> >> Signed-off-by: Wanpeng Li <[email protected]>
> >> ---
> >> arch/x86/kvm/x86.c | 7 +++++--
> >> 1 file changed, 5 insertions(+), 2 deletions(-)
> >>
> >> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> >> index a92b22f..063a643 100644
> >> --- a/arch/x86/kvm/x86.c
> >> +++ b/arch/x86/kvm/x86.c
> >> @@ -7273,10 +7273,13 @@ static int complete_emulated_mmio(struct kvm_vcpu *vcpu)
> >>
> >> int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
> >> {
> >> - struct fpu *fpu = ¤t->thread.fpu;
> >> + struct fpu *fpu = &vcpu->arch.user_fpu;
> >> int r;
> >>
> >> - fpu__initialize(fpu);
> >> + if (!fpu->initialized) {
> >> + fpstate_init(&fpu->state);
> >> + fpu->initialized = 1;
> >> + }
> >
> > Is there a chance of keeping using fpu__initialize() ? Duplicating the
> > code is ugly.
>
> There is a warning in fpu__initialize() which results in just
> current->thread.fpu can take advantage of.
>
> >
> > E.g. can't we simply initialize that in kvm_load_guest_fpu?
>
> We still miss to initialize qemu user FPU context for the above calltrace.
IMHO we should not really init the user FPU since we should always
load FPU then put FPU. The problem now is that for vcpus that with
vcpu_id>1 we'll first put the FPU before loading it. So, instead how
about we make sure we load the FPU first even for non-bootstrap vcpus?
And we can actually drop fpu__initialize() call, like:
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 064eba25c215..e6aed00ba968 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -7263,13 +7263,12 @@ static int complete_emulated_mmio(struct kvm_vcpu *vcpu)
int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
{
- struct fpu *fpu = ¤t->thread.fpu;
int r;
- fpu__initialize(fpu);
-
kvm_sigset_activate(vcpu);
+ kvm_load_guest_fpu(vcpu);
+
if (unlikely(vcpu->arch.mp_state == KVM_MP_STATE_UNINITIALIZED)) {
if (kvm_run->immediate_exit) {
r = -EINTR;
@@ -7295,14 +7294,12 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
}
}
- kvm_load_guest_fpu(vcpu);
-
if (unlikely(vcpu->arch.complete_userspace_io)) {
int (*cui)(struct kvm_vcpu *) = vcpu->arch.complete_userspace_io;
vcpu->arch.complete_userspace_io = NULL;
r = cui(vcpu);
if (r <= 0)
- goto out_fpu;
+ goto out;
} else
WARN_ON(vcpu->arch.pio.count || vcpu->mmio_needed);
@@ -7311,9 +7308,8 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
else
r = vcpu_run(vcpu);
-out_fpu:
- kvm_put_guest_fpu(vcpu);
out:
+ kvm_put_guest_fpu(vcpu);
post_kvm_run_save(vcpu);
kvm_sigset_deactivate(vcpu);
Thanks,
--
Peter Xu
2017-12-12 11:36 GMT+08:00 Peter Xu <[email protected]>:
> On Tue, Dec 12, 2017 at 05:51:26AM +0800, Wanpeng Li wrote:
>> 2017-12-12 4:48 GMT+08:00 David Hildenbrand <[email protected]>:
>> > On 10.12.2017 22:44, Wanpeng Li wrote:
>> >> From: Wanpeng Li <[email protected]>
>> >>
>> >> ------------[ cut here ]------------
>> >> Bad FPU state detected at kvm_put_guest_fpu+0xd8/0x2d0 [kvm], reinitializing FPU registers.
>> >> WARNING: CPU: 1 PID: 4594 at arch/x86/mm/extable.c:103 ex_handler_fprestore+0x88/0x90
>> >> CPU: 1 PID: 4594 Comm: qemu-system-x86 Tainted: G B OE 4.15.0-rc2+ #10
>> >> RIP: 0010:ex_handler_fprestore+0x88/0x90
>> >> Call Trace:
>> >> fixup_exception+0x4e/0x60
>> >> do_general_protection+0xff/0x270
>> >> general_protection+0x22/0x30
>> >> RIP: 0010:kvm_put_guest_fpu+0xd8/0x2d0 [kvm]
>> >> RSP: 0018:ffff8803d5627810 EFLAGS: 00010246
>> >> kvm_vcpu_reset+0x3b4/0x3c0 [kvm]
>> >> kvm_apic_accept_events+0x1c0/0x240 [kvm]
>> >> kvm_arch_vcpu_ioctl_run+0x1658/0x2fb0 [kvm]
>> >> kvm_vcpu_ioctl+0x479/0x880 [kvm]
>> >> do_vfs_ioctl+0x142/0x9a0
>> >> SyS_ioctl+0x74/0x80
>> >> do_syscall_64+0x15f/0x600
>> >>
>> >> This can be reproduced by running any testcase in kvm-unit-tests since
>> >> the qemu userspace FPU context is not initialized, which results in the
>> >> init path from kvm_apic_accept_events() will load/put qemu userspace
>> >> FPU context w/o initialized. In addition, w/o this splatting we still
>> >> should initialize vcpu->arch.user_fpu instead of current->thread.fpu.
>> >> This patch fixes it by initializing qemu user FPU context if it is
>> >> uninitialized before KVM_RUN.
>> >>
>> >> Cc: Paolo Bonzini <[email protected]>
>> >> Cc: Radim Krčmář <[email protected]>
>> >> Cc: Rik van Riel <[email protected]>
>> >> Cc: [email protected]
>> >> Fixes: f775b13eedee (x86,kvm: move qemu/guest FPU switching out to vcpu_run)
>> >> Signed-off-by: Wanpeng Li <[email protected]>
>> >> ---
>> >> arch/x86/kvm/x86.c | 7 +++++--
>> >> 1 file changed, 5 insertions(+), 2 deletions(-)
>> >>
>> >> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
>> >> index a92b22f..063a643 100644
>> >> --- a/arch/x86/kvm/x86.c
>> >> +++ b/arch/x86/kvm/x86.c
>> >> @@ -7273,10 +7273,13 @@ static int complete_emulated_mmio(struct kvm_vcpu *vcpu)
>> >>
>> >> int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
>> >> {
>> >> - struct fpu *fpu = ¤t->thread.fpu;
>> >> + struct fpu *fpu = &vcpu->arch.user_fpu;
>> >> int r;
>> >>
>> >> - fpu__initialize(fpu);
>> >> + if (!fpu->initialized) {
>> >> + fpstate_init(&fpu->state);
>> >> + fpu->initialized = 1;
>> >> + }
>> >
>> > Is there a chance of keeping using fpu__initialize() ? Duplicating the
>> > code is ugly.
>>
>> There is a warning in fpu__initialize() which results in just
>> current->thread.fpu can take advantage of.
>>
>> >
>> > E.g. can't we simply initialize that in kvm_load_guest_fpu?
>>
>> We still miss to initialize qemu user FPU context for the above calltrace.
>
> IMHO we should not really init the user FPU since we should always
> load FPU then put FPU. The problem now is that for vcpus that with
> vcpu_id>1 we'll first put the FPU before loading it. So, instead how
> about we make sure we load the FPU first even for non-bootstrap vcpus?
> And we can actually drop fpu__initialize() call, like:
It will introduce extra overhead for all the cases which can't enter
into vcpu_run(), I think move
fpstate_init(&vcpu->arch.user_fpu.state); to fx_init() is better.
Regards,
Wanpeng Li
2017-12-12 13:40 GMT+08:00 Wanpeng Li <[email protected]>:
> 2017-12-12 11:36 GMT+08:00 Peter Xu <[email protected]>:
>> On Tue, Dec 12, 2017 at 05:51:26AM +0800, Wanpeng Li wrote:
>>> 2017-12-12 4:48 GMT+08:00 David Hildenbrand <[email protected]>:
>>> > On 10.12.2017 22:44, Wanpeng Li wrote:
>>> >> From: Wanpeng Li <[email protected]>
>>> >>
>>> >> ------------[ cut here ]------------
>>> >> Bad FPU state detected at kvm_put_guest_fpu+0xd8/0x2d0 [kvm], reinitializing FPU registers.
>>> >> WARNING: CPU: 1 PID: 4594 at arch/x86/mm/extable.c:103 ex_handler_fprestore+0x88/0x90
>>> >> CPU: 1 PID: 4594 Comm: qemu-system-x86 Tainted: G B OE 4.15.0-rc2+ #10
>>> >> RIP: 0010:ex_handler_fprestore+0x88/0x90
>>> >> Call Trace:
>>> >> fixup_exception+0x4e/0x60
>>> >> do_general_protection+0xff/0x270
>>> >> general_protection+0x22/0x30
>>> >> RIP: 0010:kvm_put_guest_fpu+0xd8/0x2d0 [kvm]
>>> >> RSP: 0018:ffff8803d5627810 EFLAGS: 00010246
>>> >> kvm_vcpu_reset+0x3b4/0x3c0 [kvm]
>>> >> kvm_apic_accept_events+0x1c0/0x240 [kvm]
>>> >> kvm_arch_vcpu_ioctl_run+0x1658/0x2fb0 [kvm]
>>> >> kvm_vcpu_ioctl+0x479/0x880 [kvm]
>>> >> do_vfs_ioctl+0x142/0x9a0
>>> >> SyS_ioctl+0x74/0x80
>>> >> do_syscall_64+0x15f/0x600
>>> >>
>>> >> This can be reproduced by running any testcase in kvm-unit-tests since
>>> >> the qemu userspace FPU context is not initialized, which results in the
>>> >> init path from kvm_apic_accept_events() will load/put qemu userspace
>>> >> FPU context w/o initialized. In addition, w/o this splatting we still
>>> >> should initialize vcpu->arch.user_fpu instead of current->thread.fpu.
>>> >> This patch fixes it by initializing qemu user FPU context if it is
>>> >> uninitialized before KVM_RUN.
>>> >>
>>> >> Cc: Paolo Bonzini <[email protected]>
>>> >> Cc: Radim Krčmář <[email protected]>
>>> >> Cc: Rik van Riel <[email protected]>
>>> >> Cc: [email protected]
>>> >> Fixes: f775b13eedee (x86,kvm: move qemu/guest FPU switching out to vcpu_run)
>>> >> Signed-off-by: Wanpeng Li <[email protected]>
>>> >> ---
>>> >> arch/x86/kvm/x86.c | 7 +++++--
>>> >> 1 file changed, 5 insertions(+), 2 deletions(-)
>>> >>
>>> >> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
>>> >> index a92b22f..063a643 100644
>>> >> --- a/arch/x86/kvm/x86.c
>>> >> +++ b/arch/x86/kvm/x86.c
>>> >> @@ -7273,10 +7273,13 @@ static int complete_emulated_mmio(struct kvm_vcpu *vcpu)
>>> >>
>>> >> int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
>>> >> {
>>> >> - struct fpu *fpu = ¤t->thread.fpu;
>>> >> + struct fpu *fpu = &vcpu->arch.user_fpu;
>>> >> int r;
>>> >>
>>> >> - fpu__initialize(fpu);
>>> >> + if (!fpu->initialized) {
>>> >> + fpstate_init(&fpu->state);
>>> >> + fpu->initialized = 1;
>>> >> + }
>>> >
>>> > Is there a chance of keeping using fpu__initialize() ? Duplicating the
>>> > code is ugly.
>>>
>>> There is a warning in fpu__initialize() which results in just
>>> current->thread.fpu can take advantage of.
>>>
>>> >
>>> > E.g. can't we simply initialize that in kvm_load_guest_fpu?
>>>
>>> We still miss to initialize qemu user FPU context for the above calltrace.
>>
>> IMHO we should not really init the user FPU since we should always
>> load FPU then put FPU. The problem now is that for vcpus that with
>> vcpu_id>1 we'll first put the FPU before loading it. So, instead how
>> about we make sure we load the FPU first even for non-bootstrap vcpus?
>> And we can actually drop fpu__initialize() call, like:
>
> It will introduce extra overhead for all the cases which can't enter
> into vcpu_run(), I think move
> fpstate_init(&vcpu->arch.user_fpu.state); to fx_init() is better.
Paolo, which method you prefer?
Regards,
Wanpeng Li
On 11.12.2017 22:51, Wanpeng Li wrote:
> 2017-12-12 4:48 GMT+08:00 David Hildenbrand <[email protected]>:
>> On 10.12.2017 22:44, Wanpeng Li wrote:
>>> From: Wanpeng Li <[email protected]>
>>>
>>> ------------[ cut here ]------------
>>> Bad FPU state detected at kvm_put_guest_fpu+0xd8/0x2d0 [kvm], reinitializing FPU registers.
>>> WARNING: CPU: 1 PID: 4594 at arch/x86/mm/extable.c:103 ex_handler_fprestore+0x88/0x90
>>> CPU: 1 PID: 4594 Comm: qemu-system-x86 Tainted: G B OE 4.15.0-rc2+ #10
>>> RIP: 0010:ex_handler_fprestore+0x88/0x90
>>> Call Trace:
>>> fixup_exception+0x4e/0x60
>>> do_general_protection+0xff/0x270
>>> general_protection+0x22/0x30
>>> RIP: 0010:kvm_put_guest_fpu+0xd8/0x2d0 [kvm]
>>> RSP: 0018:ffff8803d5627810 EFLAGS: 00010246
>>> kvm_vcpu_reset+0x3b4/0x3c0 [kvm]
>>> kvm_apic_accept_events+0x1c0/0x240 [kvm]
>>> kvm_arch_vcpu_ioctl_run+0x1658/0x2fb0 [kvm]
>>> kvm_vcpu_ioctl+0x479/0x880 [kvm]
>>> do_vfs_ioctl+0x142/0x9a0
>>> SyS_ioctl+0x74/0x80
>>> do_syscall_64+0x15f/0x600
>>>
>>> This can be reproduced by running any testcase in kvm-unit-tests since
>>> the qemu userspace FPU context is not initialized, which results in the
>>> init path from kvm_apic_accept_events() will load/put qemu userspace
>>> FPU context w/o initialized. In addition, w/o this splatting we still
>>> should initialize vcpu->arch.user_fpu instead of current->thread.fpu.
>>> This patch fixes it by initializing qemu user FPU context if it is
>>> uninitialized before KVM_RUN.
>>>
>>> Cc: Paolo Bonzini <[email protected]>
>>> Cc: Radim Krčmář <[email protected]>
>>> Cc: Rik van Riel <[email protected]>
>>> Cc: [email protected]
>>> Fixes: f775b13eedee (x86,kvm: move qemu/guest FPU switching out to vcpu_run)
>>> Signed-off-by: Wanpeng Li <[email protected]>
>>> ---
>>> arch/x86/kvm/x86.c | 7 +++++--
>>> 1 file changed, 5 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
>>> index a92b22f..063a643 100644
>>> --- a/arch/x86/kvm/x86.c
>>> +++ b/arch/x86/kvm/x86.c
>>> @@ -7273,10 +7273,13 @@ static int complete_emulated_mmio(struct kvm_vcpu *vcpu)
>>>
>>> int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
>>> {
>>> - struct fpu *fpu = ¤t->thread.fpu;
>>> + struct fpu *fpu = &vcpu->arch.user_fpu;
>>> int r;
>>>
>>> - fpu__initialize(fpu);
>>> + if (!fpu->initialized) {
>>> + fpstate_init(&fpu->state);
>>> + fpu->initialized = 1;
>>> + }
>>
>> Is there a chance of keeping using fpu__initialize() ? Duplicating the
>> code is ugly.
>
> There is a warning in fpu__initialize() which results in just
> current->thread.fpu can take advantage of.
Wonder if it would make more sense to
a) drop the WARN
b) introduce a new variant without the WARN (the existing one can call this)
Manual initialization looks ugly.
>
>>
>> E.g. can't we simply initialize that in kvm_load_guest_fpu?
>
> We still miss to initialize qemu user FPU context for the above calltrace.
As load will happen before store we should be fine. But I guess it will
result in the same problem.
>
> Regards,
> Wanpeng Li
>
--
Thanks,
David / dhildenb
2017-12-12 17:40 GMT+08:00 David Hildenbrand <[email protected]>:
> On 11.12.2017 22:51, Wanpeng Li wrote:
>> 2017-12-12 4:48 GMT+08:00 David Hildenbrand <[email protected]>:
>>> On 10.12.2017 22:44, Wanpeng Li wrote:
>>>> From: Wanpeng Li <[email protected]>
>>>>
>>>> ------------[ cut here ]------------
>>>> Bad FPU state detected at kvm_put_guest_fpu+0xd8/0x2d0 [kvm], reinitializing FPU registers.
>>>> WARNING: CPU: 1 PID: 4594 at arch/x86/mm/extable.c:103 ex_handler_fprestore+0x88/0x90
>>>> CPU: 1 PID: 4594 Comm: qemu-system-x86 Tainted: G B OE 4.15.0-rc2+ #10
>>>> RIP: 0010:ex_handler_fprestore+0x88/0x90
>>>> Call Trace:
>>>> fixup_exception+0x4e/0x60
>>>> do_general_protection+0xff/0x270
>>>> general_protection+0x22/0x30
>>>> RIP: 0010:kvm_put_guest_fpu+0xd8/0x2d0 [kvm]
>>>> RSP: 0018:ffff8803d5627810 EFLAGS: 00010246
>>>> kvm_vcpu_reset+0x3b4/0x3c0 [kvm]
>>>> kvm_apic_accept_events+0x1c0/0x240 [kvm]
>>>> kvm_arch_vcpu_ioctl_run+0x1658/0x2fb0 [kvm]
>>>> kvm_vcpu_ioctl+0x479/0x880 [kvm]
>>>> do_vfs_ioctl+0x142/0x9a0
>>>> SyS_ioctl+0x74/0x80
>>>> do_syscall_64+0x15f/0x600
>>>>
>>>> This can be reproduced by running any testcase in kvm-unit-tests since
>>>> the qemu userspace FPU context is not initialized, which results in the
>>>> init path from kvm_apic_accept_events() will load/put qemu userspace
>>>> FPU context w/o initialized. In addition, w/o this splatting we still
>>>> should initialize vcpu->arch.user_fpu instead of current->thread.fpu.
>>>> This patch fixes it by initializing qemu user FPU context if it is
>>>> uninitialized before KVM_RUN.
>>>>
>>>> Cc: Paolo Bonzini <[email protected]>
>>>> Cc: Radim Krčmář <[email protected]>
>>>> Cc: Rik van Riel <[email protected]>
>>>> Cc: [email protected]
>>>> Fixes: f775b13eedee (x86,kvm: move qemu/guest FPU switching out to vcpu_run)
>>>> Signed-off-by: Wanpeng Li <[email protected]>
>>>> ---
>>>> arch/x86/kvm/x86.c | 7 +++++--
>>>> 1 file changed, 5 insertions(+), 2 deletions(-)
>>>>
>>>> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
>>>> index a92b22f..063a643 100644
>>>> --- a/arch/x86/kvm/x86.c
>>>> +++ b/arch/x86/kvm/x86.c
>>>> @@ -7273,10 +7273,13 @@ static int complete_emulated_mmio(struct kvm_vcpu *vcpu)
>>>>
>>>> int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
>>>> {
>>>> - struct fpu *fpu = ¤t->thread.fpu;
>>>> + struct fpu *fpu = &vcpu->arch.user_fpu;
>>>> int r;
>>>>
>>>> - fpu__initialize(fpu);
>>>> + if (!fpu->initialized) {
>>>> + fpstate_init(&fpu->state);
>>>> + fpu->initialized = 1;
>>>> + }
>>>
>>> Is there a chance of keeping using fpu__initialize() ? Duplicating the
>>> code is ugly.
>>
>> There is a warning in fpu__initialize() which results in just
>> current->thread.fpu can take advantage of.
>
> Wonder if it would make more sense to
>
> a) drop the WARN
> b) introduce a new variant without the WARN (the existing one can call this)
>
> Manual initialization looks ugly.
How about this? https://lkml.org/lkml/2017/12/12/5
Regards,
Wanpeng Li
On 12/12/2017 06:40, Wanpeng Li wrote:
> 2017-12-12 11:36 GMT+08:00 Peter Xu <[email protected]>:
>> On Tue, Dec 12, 2017 at 05:51:26AM +0800, Wanpeng Li wrote:
>>> 2017-12-12 4:48 GMT+08:00 David Hildenbrand <[email protected]>:
>>>> On 10.12.2017 22:44, Wanpeng Li wrote:
>>>>> From: Wanpeng Li <[email protected]>
>>>>>
>>>>> ------------[ cut here ]------------
>>>>> Bad FPU state detected at kvm_put_guest_fpu+0xd8/0x2d0 [kvm], reinitializing FPU registers.
>>>>> WARNING: CPU: 1 PID: 4594 at arch/x86/mm/extable.c:103 ex_handler_fprestore+0x88/0x90
>>>>> CPU: 1 PID: 4594 Comm: qemu-system-x86 Tainted: G B OE 4.15.0-rc2+ #10
>>>>> RIP: 0010:ex_handler_fprestore+0x88/0x90
>>>>> Call Trace:
>>>>> fixup_exception+0x4e/0x60
>>>>> do_general_protection+0xff/0x270
>>>>> general_protection+0x22/0x30
>>>>> RIP: 0010:kvm_put_guest_fpu+0xd8/0x2d0 [kvm]
>>>>> RSP: 0018:ffff8803d5627810 EFLAGS: 00010246
>>>>> kvm_vcpu_reset+0x3b4/0x3c0 [kvm]
>>>>> kvm_apic_accept_events+0x1c0/0x240 [kvm]
>>>>> kvm_arch_vcpu_ioctl_run+0x1658/0x2fb0 [kvm]
>>>>> kvm_vcpu_ioctl+0x479/0x880 [kvm]
>>>>> do_vfs_ioctl+0x142/0x9a0
>>>>> SyS_ioctl+0x74/0x80
>>>>> do_syscall_64+0x15f/0x600
>>>>>
>>>>> This can be reproduced by running any testcase in kvm-unit-tests since
>>>>> the qemu userspace FPU context is not initialized, which results in the
>>>>> init path from kvm_apic_accept_events() will load/put qemu userspace
>>>>> FPU context w/o initialized. In addition, w/o this splatting we still
>>>>> should initialize vcpu->arch.user_fpu instead of current->thread.fpu.
>>>>> This patch fixes it by initializing qemu user FPU context if it is
>>>>> uninitialized before KVM_RUN.
>>>>>
>>>>> Cc: Paolo Bonzini <[email protected]>
>>>>> Cc: Radim Krčmář <[email protected]>
>>>>> Cc: Rik van Riel <[email protected]>
>>>>> Cc: [email protected]
>>>>> Fixes: f775b13eedee (x86,kvm: move qemu/guest FPU switching out to vcpu_run)
>>>>> Signed-off-by: Wanpeng Li <[email protected]>
>>>>> ---
>>>>> arch/x86/kvm/x86.c | 7 +++++--
>>>>> 1 file changed, 5 insertions(+), 2 deletions(-)
>>>>>
>>>>> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
>>>>> index a92b22f..063a643 100644
>>>>> --- a/arch/x86/kvm/x86.c
>>>>> +++ b/arch/x86/kvm/x86.c
>>>>> @@ -7273,10 +7273,13 @@ static int complete_emulated_mmio(struct kvm_vcpu *vcpu)
>>>>>
>>>>> int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
>>>>> {
>>>>> - struct fpu *fpu = ¤t->thread.fpu;
>>>>> + struct fpu *fpu = &vcpu->arch.user_fpu;
>>>>> int r;
>>>>>
>>>>> - fpu__initialize(fpu);
>>>>> + if (!fpu->initialized) {
>>>>> + fpstate_init(&fpu->state);
>>>>> + fpu->initialized = 1;
>>>>> + }
>>>>
>>>> Is there a chance of keeping using fpu__initialize() ? Duplicating the
>>>> code is ugly.
>>>
>>> There is a warning in fpu__initialize() which results in just
>>> current->thread.fpu can take advantage of.
>>>
>>>>
>>>> E.g. can't we simply initialize that in kvm_load_guest_fpu?
>>>
>>> We still miss to initialize qemu user FPU context for the above calltrace.
>>
>> IMHO we should not really init the user FPU since we should always
>> load FPU then put FPU. The problem now is that for vcpus that with
>> vcpu_id>1 we'll first put the FPU before loading it. So, instead how
>> about we make sure we load the FPU first even for non-bootstrap vcpus?
>> And we can actually drop fpu__initialize() call, like:
>
> It will introduce extra overhead for all the cases which can't enter
> into vcpu_run(), I think move
> fpstate_init(&vcpu->arch.user_fpu.state); to fx_init() is better.
Those cases with a sleeping AP are so rare that they don't matter. They
will occur only a few times per boot. Peter's solution is right, I've
queued it.
Thanks to both!
Paolo
Paolo
2017-12-13 0:16 GMT+08:00 Paolo Bonzini <[email protected]>:
> On 12/12/2017 06:40, Wanpeng Li wrote:
>> 2017-12-12 11:36 GMT+08:00 Peter Xu <[email protected]>:
>>> On Tue, Dec 12, 2017 at 05:51:26AM +0800, Wanpeng Li wrote:
>>>> 2017-12-12 4:48 GMT+08:00 David Hildenbrand <[email protected]>:
>>>>> On 10.12.2017 22:44, Wanpeng Li wrote:
>>>>>> From: Wanpeng Li <[email protected]>
>>>>>>
>>>>>> ------------[ cut here ]------------
>>>>>> Bad FPU state detected at kvm_put_guest_fpu+0xd8/0x2d0 [kvm], reinitializing FPU registers.
>>>>>> WARNING: CPU: 1 PID: 4594 at arch/x86/mm/extable.c:103 ex_handler_fprestore+0x88/0x90
>>>>>> CPU: 1 PID: 4594 Comm: qemu-system-x86 Tainted: G B OE 4.15.0-rc2+ #10
>>>>>> RIP: 0010:ex_handler_fprestore+0x88/0x90
>>>>>> Call Trace:
>>>>>> fixup_exception+0x4e/0x60
>>>>>> do_general_protection+0xff/0x270
>>>>>> general_protection+0x22/0x30
>>>>>> RIP: 0010:kvm_put_guest_fpu+0xd8/0x2d0 [kvm]
>>>>>> RSP: 0018:ffff8803d5627810 EFLAGS: 00010246
>>>>>> kvm_vcpu_reset+0x3b4/0x3c0 [kvm]
>>>>>> kvm_apic_accept_events+0x1c0/0x240 [kvm]
>>>>>> kvm_arch_vcpu_ioctl_run+0x1658/0x2fb0 [kvm]
>>>>>> kvm_vcpu_ioctl+0x479/0x880 [kvm]
>>>>>> do_vfs_ioctl+0x142/0x9a0
>>>>>> SyS_ioctl+0x74/0x80
>>>>>> do_syscall_64+0x15f/0x600
>>>>>>
>>>>>> This can be reproduced by running any testcase in kvm-unit-tests since
>>>>>> the qemu userspace FPU context is not initialized, which results in the
>>>>>> init path from kvm_apic_accept_events() will load/put qemu userspace
>>>>>> FPU context w/o initialized. In addition, w/o this splatting we still
>>>>>> should initialize vcpu->arch.user_fpu instead of current->thread.fpu.
>>>>>> This patch fixes it by initializing qemu user FPU context if it is
>>>>>> uninitialized before KVM_RUN.
>>>>>>
>>>>>> Cc: Paolo Bonzini <[email protected]>
>>>>>> Cc: Radim Krčmář <[email protected]>
>>>>>> Cc: Rik van Riel <[email protected]>
>>>>>> Cc: [email protected]
>>>>>> Fixes: f775b13eedee (x86,kvm: move qemu/guest FPU switching out to vcpu_run)
>>>>>> Signed-off-by: Wanpeng Li <[email protected]>
>>>>>> ---
>>>>>> arch/x86/kvm/x86.c | 7 +++++--
>>>>>> 1 file changed, 5 insertions(+), 2 deletions(-)
>>>>>>
>>>>>> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
>>>>>> index a92b22f..063a643 100644
>>>>>> --- a/arch/x86/kvm/x86.c
>>>>>> +++ b/arch/x86/kvm/x86.c
>>>>>> @@ -7273,10 +7273,13 @@ static int complete_emulated_mmio(struct kvm_vcpu *vcpu)
>>>>>>
>>>>>> int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
>>>>>> {
>>>>>> - struct fpu *fpu = ¤t->thread.fpu;
>>>>>> + struct fpu *fpu = &vcpu->arch.user_fpu;
>>>>>> int r;
>>>>>>
>>>>>> - fpu__initialize(fpu);
>>>>>> + if (!fpu->initialized) {
>>>>>> + fpstate_init(&fpu->state);
>>>>>> + fpu->initialized = 1;
>>>>>> + }
>>>>>
>>>>> Is there a chance of keeping using fpu__initialize() ? Duplicating the
>>>>> code is ugly.
>>>>
>>>> There is a warning in fpu__initialize() which results in just
>>>> current->thread.fpu can take advantage of.
>>>>
>>>>>
>>>>> E.g. can't we simply initialize that in kvm_load_guest_fpu?
>>>>
>>>> We still miss to initialize qemu user FPU context for the above calltrace.
>>>
>>> IMHO we should not really init the user FPU since we should always
>>> load FPU then put FPU. The problem now is that for vcpus that with
>>> vcpu_id>1 we'll first put the FPU before loading it. So, instead how
>>> about we make sure we load the FPU first even for non-bootstrap vcpus?
>>> And we can actually drop fpu__initialize() call, like:
>>
>> It will introduce extra overhead for all the cases which can't enter
>> into vcpu_run(), I think move
>> fpstate_init(&vcpu->arch.user_fpu.state); to fx_init() is better.
>
> Those cases with a sleeping AP are so rare that they don't matter. They
> will occur only a few times per boot. Peter's solution is right, I've
> queued it.
I add a trace_printk here to test Peter's solution:
if (unlikely(vcpu->arch.mp_state == KVM_MP_STATE_UNINITIALIZED)) {
if (kvm_run->immediate_exit) {
r = -EINTR;
goto out;
}
kvm_vcpu_block(vcpu);
kvm_apic_accept_events(vcpu);
kvm_clear_request(KVM_REQ_UNHALT, vcpu);
r = -EAGAIN;
if (signal_pending(current)) {
r = -EINTR;
vcpu->run->exit_reason = KVM_EXIT_INTR;
++vcpu->stat.signal_exits;
}
trace_printk("load/put make no sense\n");
goto out;
}
I can observe 92339 times "load/put make no sense" in the log during a
32 vCPUs guest booting on a 32 pCPUs Xeon Skylake server. The print
frequency is as below:
<...>-207694 [016] .... 1021785.120346:
kvm_arch_vcpu_ioctl_run: load/put make no sense
<...>-207704 [031] .... 1021785.120347:
kvm_arch_vcpu_ioctl_run: load/put make no sense
<...>-207710 [005] .... 1021785.120349:
kvm_arch_vcpu_ioctl_run: load/put make no sense
<...>-207687 [002] .... 1021785.120351:
kvm_arch_vcpu_ioctl_run: load/put make no sense
<...>-207709 [018] .... 1021785.120353:
kvm_arch_vcpu_ioctl_run: load/put make no sense
<...>-207687 [002] .... 1021785.120354:
kvm_arch_vcpu_ioctl_run: load/put make no sense
<...>-207692 [004] .... 1021785.120354:
kvm_arch_vcpu_ioctl_run: load/put make no sense
<...>-207698 [015] .... 1021785.120358:
kvm_arch_vcpu_ioctl_run: load/put make no sense
<...>-207702 [029] .... 1021785.120358:
kvm_arch_vcpu_ioctl_run: load/put make no sense
<...>-207715 [026] .... 1021785.120361:
kvm_arch_vcpu_ioctl_run: load/put make no sense
<...>-207707 [013] .... 1021785.120362:
kvm_arch_vcpu_ioctl_run: load/put make no sense
<...>-207712 [022] .... 1021785.120365:
kvm_arch_vcpu_ioctl_run: load/put make no sense
<...>-207711 [006] .... 1021785.120365:
kvm_arch_vcpu_ioctl_run: load/put make no sense
<...>-207695 [000] .... 1021785.120367:
kvm_arch_vcpu_ioctl_run: load/put make no sense
<...>-207689 [027] .... 1021785.120367:
kvm_arch_vcpu_ioctl_run: load/put make no sense
<...>-207703 [011] .... 1021785.120368:
kvm_arch_vcpu_ioctl_run: load/put make no sense
<...>-207708 [007] .... 1021785.120370:
kvm_arch_vcpu_ioctl_run: load/put make no sense
<...>-207692 [004] .... 1021785.120371:
kvm_arch_vcpu_ioctl_run: load/put make no sense
<...>-207708 [007] .... 1021785.120372:
kvm_arch_vcpu_ioctl_run: load/put make no sense
<...>-207708 [007] .... 1021785.120373:
kvm_arch_vcpu_ioctl_run: load/put make no sense
<...>-207698 [015] .... 1021785.120374:
kvm_arch_vcpu_ioctl_run: load/put make no sense
<...>-207713 [012] .... 1021785.120375:
kvm_arch_vcpu_ioctl_run: load/put make no sense
<...>-207690 [028] .... 1021785.120376:
kvm_arch_vcpu_ioctl_run: load/put make no sense
I will send out the fx_init() solution, you can pick it if it makes sense. :)
Regards,
Wanpeng Li