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* Re: [PATCH] KVM: nVMX: set rflags to specify success in handle_invvpid() default case
@ 2020-01-23  9:36 linmiaohe
  0 siblings, 0 replies; 12+ messages in thread
From: linmiaohe @ 2020-01-23  9:36 UTC (permalink / raw)
  To: Paolo Bonzini, Vitaly Kuznetsov
  Cc: kvm, linux-kernel, x86, rkrcmar, sean.j.christopherson,
	wanpengli, jmattson, joro, tglx, mingo, bp, hpa

Paolo Bonzini <pbonzini@redhat.com> wrote:
> On 23/01/20 09:55, Vitaly Kuznetsov wrote:
> > Your patch seems to do the right thing, however, I started wondering 
> > if
> > WARN_ON_ONCE() is the right thing to do. SDM says that "If an 
> > unsupported INVVPID type is specified, the instruction fails." and 
> > this is similar to INVEPT and I decided to check what handle_invept() 
> > does. Well, it does BUG_ON().
> > 
> > Are we doing the right thing in any of these cases?
>
> Yes, both INVEPT and INVVPID catch this earlier.
>
> For INVEPT:
>
>         types = (vmx->nested.msrs.ept_caps >> VMX_EPT_EXTENT_SHIFT) & 6;
>
>         if (type >= 32 || !(types & (1 << type)))
>                 return nested_vmx_failValid(vcpu,
>                                 VMXERR_INVALID_OPERAND_TO_INVEPT_INVVPID);
>
>
>
> For INVVPID:
>
>         types = (vmx->nested.msrs.vpid_caps &
>                         VMX_VPID_EXTENT_SUPPORTED_MASK) >> 8;
>
>         if (type >= 32 || !(types & (1 << type)))
>                 return nested_vmx_failValid(vcpu,
>                         VMXERR_INVALID_OPERAND_TO_INVEPT_INVVPID);
>
> So I'm leaning towards not applying Miaohe's patch.  Happy Mouse Year to everyone, here is an ASCII art (except for one Unicode character) mouse:
>
>
>        __()()
>       /     o)
>   ~~~~\_,__,_>°
>
> Thanks,

Yes, it seems my patch is meaningless. And thanks for both of your review and reply.
Happy Mouse Year and I catch a mickey mouse:

   ###########
  ###############        __-----__          ##
##################    ###          \       ####
################## #### #            \     # ##
 ####################            \~~\  \   ,##",
  #################       /~~\    \## \  \"     :
    ###############       \    \   \##" /       :
              #######       \### \    /         :
              #############  \###/             :
               ########                       :
                ######   __                  :
                 ####   /\                  /
      ############ ###    \\______________/|
    ##################     \ __         / /
  ####################\__    \  \---\,/ /
  ###################    \     \_____/ /
   #################       \_________/
    ###############
      ###########

Thanks both again.

^ permalink raw reply	[flat|nested] 12+ messages in thread

* Re: [PATCH] KVM: nVMX: set rflags to specify success in handle_invvpid() default case
@ 2020-02-04  1:06 linmiaohe
  0 siblings, 0 replies; 12+ messages in thread
From: linmiaohe @ 2020-02-04  1:06 UTC (permalink / raw)
  To: Vitaly Kuznetsov; +Cc: kvm list, LKML, the arch/x86 maintainers

Vitaly Kuznetsov <vkuznets@redhat.com> writes:

> linmiaohe <linmiaohe@huawei.com> writes:
>
> > I'm sorry for reply in such a big day. I'am just backing from a really 
> > hard festival. :(
>
> Let the force be with you guys! We really hope the madness is going to be over soon. Stay safe!
>

Many thanks! I believe we will defeat it soon ! Best wishes with you! Thanks again! :)


^ permalink raw reply	[flat|nested] 12+ messages in thread

* Re: [PATCH] KVM: nVMX: set rflags to specify success in handle_invvpid() default case
  2020-02-03  3:29 linmiaohe
@ 2020-02-03  9:48 ` Vitaly Kuznetsov
  0 siblings, 0 replies; 12+ messages in thread
From: Vitaly Kuznetsov @ 2020-02-03  9:48 UTC (permalink / raw)
  To: linmiaohe
  Cc: kvm list, LKML, the arch/x86 maintainers,
	Radim Krčmář,
	Wanpeng Li, Joerg Roedel, Thomas Gleixner, Ingo Molnar,
	Borislav Petkov, H . Peter Anvin, Paolo Bonzini,
	Sean Christopherson, Jim Mattson

linmiaohe <linmiaohe@huawei.com> writes:

> I'm sorry for reply in such a big day. I'am just backing from a really
> hard festival. :(

Let the force be with you guys! We really hope the madness is going to
be over soon. Stay safe!

-- 
Vitaly


^ permalink raw reply	[flat|nested] 12+ messages in thread

* Re: [PATCH] KVM: nVMX: set rflags to specify success in handle_invvpid() default case
@ 2020-02-03  3:29 linmiaohe
  2020-02-03  9:48 ` Vitaly Kuznetsov
  0 siblings, 1 reply; 12+ messages in thread
From: linmiaohe @ 2020-02-03  3:29 UTC (permalink / raw)
  To: Vitaly Kuznetsov, Paolo Bonzini, Sean Christopherson, Jim Mattson
  Cc: kvm list, LKML, the arch/x86 maintainers,
	Radim Krčmář,
	Wanpeng Li, Joerg Roedel, Thomas Gleixner, Ingo Molnar,
	Borislav Petkov, H . Peter Anvin

Vitaly Kuznetsov <vkuznets@redhat.com> writes:
> Sean Christopherson <sean.j.christopherson@intel.com> writes:
>> On Thu, Jan 23, 2020 at 10:22:24AM -0800, Jim Mattson wrote:
>>> On Thu, Jan 23, 2020 at 1:54 AM Paolo Bonzini <pbonzini@redhat.com> wrote:
>>> >
>>> > On 23/01/20 10:45, Vitaly Kuznetsov wrote:
>>> > >>> SDM says that "If an
>>> > >>> unsupported INVVPID type is specified, the instruction fails." 
>>> > >>> and this is similar to INVEPT and I decided to check what 
>>> > >>> handle_invept() does. Well, it does BUG_ON().
>>> > >>>
>>> > >>> Are we doing the right thing in any of these cases?
>>> > >>
>>> > >> Yes, both INVEPT and INVVPID catch this earlier.
>>> > >>
>>> > >> So I'm leaning towards not applying Miaohe's patch.
>>> > >
>>> > > Well, we may at least want to converge on BUG_ON() for both 
>>> > > handle_invvpid()/handle_invept(), there's no need for them to differ.
>>> >
>>> > WARN_ON_ONCE + nested_vmx_failValid would probably be better, if we 
>>> > really want to change this.
>>> >
>>> > Paolo
>>> 
>>> In both cases, something is seriously wrong. The only plausible 
>>> explanations are compiler error or hardware failure. It would be nice 
>>> to handle *all* such failures with a KVM_INTERNAL_ERROR exit to 
>>> userspace. (I'm also thinking of situations like getting a VM-exit 
>> for
>>>> INIT.)
>>
>> Ya.  Vitaly and I had a similar discussion[*].  The idea we tossed 
>> around was to also mark the VM as having encountered a KVM/hardware 
>> bug so that the VM is effectively dead.  That would also allow 
>> gracefully handling bugs that are detected deep in the stack, i.e. 
>> can't simply return 0 to get out to userspace.
>
>Yea, I was thinking about introducing a big hammer which would stop the whole VM as soon as possible to make it easier to debug such situations. Something like (not really tested):
>
Yea, please just ignore my origin patch and do what you want. :)
I'm sorry for reply in such a big day. I'am just backing from a really hard festival. :(

^ permalink raw reply	[flat|nested] 12+ messages in thread

* Re: [PATCH] KVM: nVMX: set rflags to specify success in handle_invvpid() default case
  2020-01-23 23:01           ` Sean Christopherson
@ 2020-01-24 10:53             ` Vitaly Kuznetsov
  0 siblings, 0 replies; 12+ messages in thread
From: Vitaly Kuznetsov @ 2020-01-24 10:53 UTC (permalink / raw)
  To: Paolo Bonzini, Sean Christopherson, Jim Mattson
  Cc: linmiaohe, kvm list, LKML, the arch/x86 maintainers,
	Radim Krčmář,
	Wanpeng Li, Joerg Roedel, Thomas Gleixner, Ingo Molnar,
	Borislav Petkov, H . Peter Anvin

Sean Christopherson <sean.j.christopherson@intel.com> writes:

> On Thu, Jan 23, 2020 at 10:22:24AM -0800, Jim Mattson wrote:
>> On Thu, Jan 23, 2020 at 1:54 AM Paolo Bonzini <pbonzini@redhat.com> wrote:
>> >
>> > On 23/01/20 10:45, Vitaly Kuznetsov wrote:
>> > >>> SDM says that "If an
>> > >>> unsupported INVVPID type is specified, the instruction fails." and this
>> > >>> is similar to INVEPT and I decided to check what handle_invept()
>> > >>> does. Well, it does BUG_ON().
>> > >>>
>> > >>> Are we doing the right thing in any of these cases?
>> > >>
>> > >> Yes, both INVEPT and INVVPID catch this earlier.
>> > >>
>> > >> So I'm leaning towards not applying Miaohe's patch.
>> > >
>> > > Well, we may at least want to converge on BUG_ON() for both
>> > > handle_invvpid()/handle_invept(), there's no need for them to differ.
>> >
>> > WARN_ON_ONCE + nested_vmx_failValid would probably be better, if we
>> > really want to change this.
>> >
>> > Paolo
>> 
>> In both cases, something is seriously wrong. The only plausible
>> explanations are compiler error or hardware failure. It would be nice
>> to handle *all* such failures with a KVM_INTERNAL_ERROR exit to
>> userspace. (I'm also thinking of situations like getting a VM-exit for
>> INIT.)
>
> Ya.  Vitaly and I had a similar discussion[*].  The idea we tossed around
> was to also mark the VM as having encountered a KVM/hardware bug so that
> the VM is effectively dead.  That would also allow gracefully handling bugs
> that are detected deep in the stack, i.e. can't simply return 0 to get out
> to userspace.

Yea, I was thinking about introducing a big hammer which would stop the
whole VM as soon as possible to make it easier to debug such
situations. Something like (not really tested):

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index cf917139de6b..5476f88c9ada 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -8001,6 +8001,15 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
 	bool req_immediate_exit = false;
 
 	if (kvm_request_pending(vcpu)) {
+		/* INTERROR check should always come first */
+		if (kvm_check_request(KVM_REQ_INTERROR, vcpu)) {
+			if (vcpu->run->exit_reason != KVM_EXIT_INTERNAL_ERROR) {
+				vcpu->run->exit_reason = KVM_EXIT_INTERNAL_ERROR;
+				vcpu->run->internal.suberror = KVM_INTERNAL_ERROR_OTHERCPU;
+			}
+			r = 0;
+			goto out;
+		}
 		if (kvm_check_request(KVM_REQ_GET_VMCS12_PAGES, vcpu)) {
 			if (unlikely(!kvm_x86_ops->get_vmcs12_pages(vcpu))) {
 				r = 0;
@@ -8510,6 +8519,13 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
 	kvm_sigset_activate(vcpu);
 	kvm_load_guest_fpu(vcpu);
 
+	if (unlikely(vcpu->kvm->vm_bugged)) {
+		vcpu->run->exit_reason = KVM_REQ_INTERROR;
+		/* Maybe a suberror for 'attempted to run a vCPU of a bugged VM? */
+		r = 0;
+		goto out;
+	}
+
 	if (unlikely(vcpu->arch.mp_state == KVM_MP_STATE_UNINITIALIZED)) {
 		if (kvm_run->immediate_exit) {
 			r = -EINTR;
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 538c25e778c0..d003be5fcf42 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -146,6 +146,7 @@ static inline bool is_error_page(struct page *page)
 #define KVM_REQ_MMU_RELOAD        (1 | KVM_REQUEST_WAIT | KVM_REQUEST_NO_WAKEUP)
 #define KVM_REQ_PENDING_TIMER     2
 #define KVM_REQ_UNHALT            3
+#define KVM_REQ_INTERROR          (4 | KVM_REQUEST_WAIT)
 #define KVM_REQUEST_ARCH_BASE     8
 
 #define KVM_ARCH_REQ_FLAGS(nr, flags) ({ \
@@ -501,6 +502,9 @@ struct kvm {
 	struct srcu_struct srcu;
 	struct srcu_struct irq_srcu;
 	pid_t userspace_pid;
+
+	/* VM caused internal KVM error */
+	bool vm_bugged;
 };
 
 #define kvm_err(fmt, ...) \
@@ -613,6 +617,7 @@ static inline void kvm_irqfd_exit(void)
 int kvm_init(void *opaque, unsigned vcpu_size, unsigned vcpu_align,
 		  struct module *module);
 void kvm_exit(void);
+void kvm_vm_bug(struct kvm_vcpu *vcpu, u32 error);
 
 void kvm_get_kvm(struct kvm *kvm);
 void kvm_put_kvm(struct kvm *kvm);
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index f0a16b4adbbd..62505161ae98 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -246,6 +246,8 @@ struct kvm_hyperv_exit {
 #define KVM_INTERNAL_ERROR_DELIVERY_EV	3
 /* Encounter unexpected vm-exit reason */
 #define KVM_INTERNAL_ERROR_UNEXPECTED_EXIT_REASON	4
+/* Some other vCPU caused internal KVM error */
+#define KVM_INTERNAL_ERROR_OTHERCPU	5
 
 /* for KVM_RUN, returned by mmap(vcpu_fd, offset=0) */
 struct kvm_run {
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 00268290dcbd..4cc268d57714 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -4446,6 +4446,18 @@ void kvm_exit(void)
 }
 EXPORT_SYMBOL_GPL(kvm_exit);
 
+void kvm_vm_bug(struct kvm_vcpu *vcpu, u32 error)
+{
+	vcpu->kvm->vm_bugged = true;
+
+	vcpu->run->exit_reason = KVM_EXIT_INTERNAL_ERROR;
+	vcpu->run->internal.suberror = error;
+	/* We can also pass ndata/data ... */
+
+	kvm_make_all_cpus_request(vcpu->kvm, KVM_REQ_INTERROR);
+}
+EXPORT_SYMBOL_GPL(kvm_vm_bug);
+
 struct kvm_vm_worker_thread_context {
 	struct kvm *kvm;
 	struct task_struct *parent;

If you guys like the idea in general I can prepare patches.

-- 
Vitaly


^ permalink raw reply related	[flat|nested] 12+ messages in thread

* Re: [PATCH] KVM: nVMX: set rflags to specify success in handle_invvpid() default case
  2020-01-23 18:22         ` Jim Mattson
@ 2020-01-23 23:01           ` Sean Christopherson
  2020-01-24 10:53             ` Vitaly Kuznetsov
  0 siblings, 1 reply; 12+ messages in thread
From: Sean Christopherson @ 2020-01-23 23:01 UTC (permalink / raw)
  To: Jim Mattson
  Cc: Paolo Bonzini, Vitaly Kuznetsov, linmiaohe, kvm list, LKML,
	the arch/x86 maintainers, Radim Krčmář,
	Wanpeng Li, Joerg Roedel, Thomas Gleixner, Ingo Molnar,
	Borislav Petkov, H . Peter Anvin

On Thu, Jan 23, 2020 at 10:22:24AM -0800, Jim Mattson wrote:
> On Thu, Jan 23, 2020 at 1:54 AM Paolo Bonzini <pbonzini@redhat.com> wrote:
> >
> > On 23/01/20 10:45, Vitaly Kuznetsov wrote:
> > >>> SDM says that "If an
> > >>> unsupported INVVPID type is specified, the instruction fails." and this
> > >>> is similar to INVEPT and I decided to check what handle_invept()
> > >>> does. Well, it does BUG_ON().
> > >>>
> > >>> Are we doing the right thing in any of these cases?
> > >>
> > >> Yes, both INVEPT and INVVPID catch this earlier.
> > >>
> > >> So I'm leaning towards not applying Miaohe's patch.
> > >
> > > Well, we may at least want to converge on BUG_ON() for both
> > > handle_invvpid()/handle_invept(), there's no need for them to differ.
> >
> > WARN_ON_ONCE + nested_vmx_failValid would probably be better, if we
> > really want to change this.
> >
> > Paolo
> 
> In both cases, something is seriously wrong. The only plausible
> explanations are compiler error or hardware failure. It would be nice
> to handle *all* such failures with a KVM_INTERNAL_ERROR exit to
> userspace. (I'm also thinking of situations like getting a VM-exit for
> INIT.)

Ya.  Vitaly and I had a similar discussion[*].  The idea we tossed around
was to also mark the VM as having encountered a KVM/hardware bug so that
the VM is effectively dead.  That would also allow gracefully handling bugs
that are detected deep in the stack, i.e. can't simply return 0 to get out
to userspace.

[*] https://lkml.kernel.org/r/20190930153358.GD14693@linux.intel.com

^ permalink raw reply	[flat|nested] 12+ messages in thread

* Re: [PATCH] KVM: nVMX: set rflags to specify success in handle_invvpid() default case
  2020-01-23  9:54       ` Paolo Bonzini
@ 2020-01-23 18:22         ` Jim Mattson
  2020-01-23 23:01           ` Sean Christopherson
  0 siblings, 1 reply; 12+ messages in thread
From: Jim Mattson @ 2020-01-23 18:22 UTC (permalink / raw)
  To: Paolo Bonzini
  Cc: Vitaly Kuznetsov, linmiaohe, kvm list, LKML,
	the arch/x86 maintainers, Radim Krčmář,
	Sean Christopherson, Wanpeng Li, Joerg Roedel, Thomas Gleixner,
	Ingo Molnar, Borislav Petkov, H . Peter Anvin

On Thu, Jan 23, 2020 at 1:54 AM Paolo Bonzini <pbonzini@redhat.com> wrote:
>
> On 23/01/20 10:45, Vitaly Kuznetsov wrote:
> >>> SDM says that "If an
> >>> unsupported INVVPID type is specified, the instruction fails." and this
> >>> is similar to INVEPT and I decided to check what handle_invept()
> >>> does. Well, it does BUG_ON().
> >>>
> >>> Are we doing the right thing in any of these cases?
> >>
> >> Yes, both INVEPT and INVVPID catch this earlier.
> >>
> >> So I'm leaning towards not applying Miaohe's patch.
> >
> > Well, we may at least want to converge on BUG_ON() for both
> > handle_invvpid()/handle_invept(), there's no need for them to differ.
>
> WARN_ON_ONCE + nested_vmx_failValid would probably be better, if we
> really want to change this.
>
> Paolo

In both cases, something is seriously wrong. The only plausible
explanations are compiler error or hardware failure. It would be nice
to handle *all* such failures with a KVM_INTERNAL_ERROR exit to
userspace. (I'm also thinking of situations like getting a VM-exit for
INIT.)

^ permalink raw reply	[flat|nested] 12+ messages in thread

* Re: [PATCH] KVM: nVMX: set rflags to specify success in handle_invvpid() default case
  2020-01-23  9:45     ` Vitaly Kuznetsov
@ 2020-01-23  9:54       ` Paolo Bonzini
  2020-01-23 18:22         ` Jim Mattson
  0 siblings, 1 reply; 12+ messages in thread
From: Paolo Bonzini @ 2020-01-23  9:54 UTC (permalink / raw)
  To: Vitaly Kuznetsov, linmiaohe
  Cc: kvm, linux-kernel, x86, rkrcmar, sean.j.christopherson,
	wanpengli, jmattson, joro, tglx, mingo, bp, hpa

On 23/01/20 10:45, Vitaly Kuznetsov wrote:
>>> SDM says that "If an
>>> unsupported INVVPID type is specified, the instruction fails." and this
>>> is similar to INVEPT and I decided to check what handle_invept()
>>> does. Well, it does BUG_ON(). 
>>>
>>> Are we doing the right thing in any of these cases?
>>
>> Yes, both INVEPT and INVVPID catch this earlier.
>>
>> So I'm leaning towards not applying Miaohe's patch.
> 
> Well, we may at least want to converge on BUG_ON() for both
> handle_invvpid()/handle_invept(), there's no need for them to differ.

WARN_ON_ONCE + nested_vmx_failValid would probably be better, if we
really want to change this.

Paolo


^ permalink raw reply	[flat|nested] 12+ messages in thread

* Re: [PATCH] KVM: nVMX: set rflags to specify success in handle_invvpid() default case
  2020-01-23  9:23   ` Paolo Bonzini
@ 2020-01-23  9:45     ` Vitaly Kuznetsov
  2020-01-23  9:54       ` Paolo Bonzini
  0 siblings, 1 reply; 12+ messages in thread
From: Vitaly Kuznetsov @ 2020-01-23  9:45 UTC (permalink / raw)
  To: Paolo Bonzini, linmiaohe
  Cc: kvm, linux-kernel, x86, rkrcmar, sean.j.christopherson,
	wanpengli, jmattson, joro, tglx, mingo, bp, hpa

Paolo Bonzini <pbonzini@redhat.com> writes:

> On 23/01/20 09:55, Vitaly Kuznetsov wrote:
>>> diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
>>> index 7608924ee8c1..985d3307ec56 100644
>>> --- a/arch/x86/kvm/vmx/nested.c
>>> +++ b/arch/x86/kvm/vmx/nested.c
>>> @@ -5165,7 +5165,7 @@ static int handle_invvpid(struct kvm_vcpu *vcpu)
>>>  		break;
>>>  	default:
>>>  		WARN_ON_ONCE(1);
>>> -		return kvm_skip_emulated_instruction(vcpu);
>>> +		break;
>>>  	}
>>>  
>>>  	return nested_vmx_succeed(vcpu);
>> Your patch seems to do the right thing, however, I started wondering if
>> WARN_ON_ONCE() is the right thing to do. SDM says that "If an
>> unsupported INVVPID type is specified, the instruction fails." and this
>> is similar to INVEPT and I decided to check what handle_invept()
>> does. Well, it does BUG_ON(). 
>> 
>> Are we doing the right thing in any of these cases?
>
> Yes, both INVEPT and INVVPID catch this earlier.
>
> For INVEPT:
>
>         types = (vmx->nested.msrs.ept_caps >> VMX_EPT_EXTENT_SHIFT) & 6;
>
>         if (type >= 32 || !(types & (1 << type)))
>                 return nested_vmx_failValid(vcpu,
>                                 VMXERR_INVALID_OPERAND_TO_INVEPT_INVVPID);
>
>
>
> For INVVPID:
>
>         types = (vmx->nested.msrs.vpid_caps &
>                         VMX_VPID_EXTENT_SUPPORTED_MASK) >> 8;
>
>         if (type >= 32 || !(types & (1 << type)))
>                 return nested_vmx_failValid(vcpu,
>                         VMXERR_INVALID_OPERAND_TO_INVEPT_INVVPID);
>

Ah, true, thanks for checking!

> So I'm leaning towards not applying Miaohe's patch.

Well, we may at least want to converge on BUG_ON() for both
handle_invvpid()/handle_invept(), there's no need for them to differ.

-- 
Vitaly


^ permalink raw reply	[flat|nested] 12+ messages in thread

* Re: [PATCH] KVM: nVMX: set rflags to specify success in handle_invvpid() default case
  2020-01-23  8:55 ` Vitaly Kuznetsov
@ 2020-01-23  9:23   ` Paolo Bonzini
  2020-01-23  9:45     ` Vitaly Kuznetsov
  0 siblings, 1 reply; 12+ messages in thread
From: Paolo Bonzini @ 2020-01-23  9:23 UTC (permalink / raw)
  To: Vitaly Kuznetsov, linmiaohe
  Cc: kvm, linux-kernel, x86, rkrcmar, sean.j.christopherson,
	wanpengli, jmattson, joro, tglx, mingo, bp, hpa

On 23/01/20 09:55, Vitaly Kuznetsov wrote:
>> diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
>> index 7608924ee8c1..985d3307ec56 100644
>> --- a/arch/x86/kvm/vmx/nested.c
>> +++ b/arch/x86/kvm/vmx/nested.c
>> @@ -5165,7 +5165,7 @@ static int handle_invvpid(struct kvm_vcpu *vcpu)
>>  		break;
>>  	default:
>>  		WARN_ON_ONCE(1);
>> -		return kvm_skip_emulated_instruction(vcpu);
>> +		break;
>>  	}
>>  
>>  	return nested_vmx_succeed(vcpu);
> Your patch seems to do the right thing, however, I started wondering if
> WARN_ON_ONCE() is the right thing to do. SDM says that "If an
> unsupported INVVPID type is specified, the instruction fails." and this
> is similar to INVEPT and I decided to check what handle_invept()
> does. Well, it does BUG_ON(). 
> 
> Are we doing the right thing in any of these cases?

Yes, both INVEPT and INVVPID catch this earlier.

For INVEPT:

        types = (vmx->nested.msrs.ept_caps >> VMX_EPT_EXTENT_SHIFT) & 6;

        if (type >= 32 || !(types & (1 << type)))
                return nested_vmx_failValid(vcpu,
                                VMXERR_INVALID_OPERAND_TO_INVEPT_INVVPID);



For INVVPID:

        types = (vmx->nested.msrs.vpid_caps &
                        VMX_VPID_EXTENT_SUPPORTED_MASK) >> 8;

        if (type >= 32 || !(types & (1 << type)))
                return nested_vmx_failValid(vcpu,
                        VMXERR_INVALID_OPERAND_TO_INVEPT_INVVPID);

So I'm leaning towards not applying Miaohe's patch.  Happy Mouse Year
to everyone, here is an ASCII art (except for one Unicode character) mouse:


       __()()
      /     o)
  ~~~~\_,__,_>°

Thanks,


^ permalink raw reply	[flat|nested] 12+ messages in thread

* Re: [PATCH] KVM: nVMX: set rflags to specify success in handle_invvpid() default case
  2020-01-23  3:14 linmiaohe
@ 2020-01-23  8:55 ` Vitaly Kuznetsov
  2020-01-23  9:23   ` Paolo Bonzini
  0 siblings, 1 reply; 12+ messages in thread
From: Vitaly Kuznetsov @ 2020-01-23  8:55 UTC (permalink / raw)
  To: linmiaohe
  Cc: kvm, linux-kernel, x86, pbonzini, rkrcmar, sean.j.christopherson,
	wanpengli, jmattson, joro, tglx, mingo, bp, hpa

linmiaohe <linmiaohe@huawei.com> writes:

> From: Miaohe Lin <linmiaohe@huawei.com>
>
> In handle_invvpid() default case, we just skip emulated instruction and
> forget to set rflags to specify success. This would result in indefinite
> rflags value and thus indeterminate return value for guest.
>
> Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
> ---
> 	Chinese New Year is coming. Happy Spring Festival! ^_^

Happy Spring Festival!

> ---
>  arch/x86/kvm/vmx/nested.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
> index 7608924ee8c1..985d3307ec56 100644
> --- a/arch/x86/kvm/vmx/nested.c
> +++ b/arch/x86/kvm/vmx/nested.c
> @@ -5165,7 +5165,7 @@ static int handle_invvpid(struct kvm_vcpu *vcpu)
>  		break;
>  	default:
>  		WARN_ON_ONCE(1);
> -		return kvm_skip_emulated_instruction(vcpu);
> +		break;
>  	}
>  
>  	return nested_vmx_succeed(vcpu);

Your patch seems to do the right thing, however, I started wondering if
WARN_ON_ONCE() is the right thing to do. SDM says that "If an
unsupported INVVPID type is specified, the instruction fails." and this
is similar to INVEPT and I decided to check what handle_invept()
does. Well, it does BUG_ON(). 

Are we doing the right thing in any of these cases?

-- 
Vitaly


^ permalink raw reply	[flat|nested] 12+ messages in thread

* [PATCH] KVM: nVMX: set rflags to specify success in handle_invvpid() default case
@ 2020-01-23  3:14 linmiaohe
  2020-01-23  8:55 ` Vitaly Kuznetsov
  0 siblings, 1 reply; 12+ messages in thread
From: linmiaohe @ 2020-01-23  3:14 UTC (permalink / raw)
  To: pbonzini, rkrcmar, sean.j.christopherson, vkuznets, wanpengli,
	jmattson, joro, tglx, mingo, bp, hpa
  Cc: linmiaohe, kvm, linux-kernel, x86

From: Miaohe Lin <linmiaohe@huawei.com>

In handle_invvpid() default case, we just skip emulated instruction and
forget to set rflags to specify success. This would result in indefinite
rflags value and thus indeterminate return value for guest.

Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
---
	Chinese New Year is coming. Happy Spring Festival! ^_^
---
 arch/x86/kvm/vmx/nested.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index 7608924ee8c1..985d3307ec56 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -5165,7 +5165,7 @@ static int handle_invvpid(struct kvm_vcpu *vcpu)
 		break;
 	default:
 		WARN_ON_ONCE(1);
-		return kvm_skip_emulated_instruction(vcpu);
+		break;
 	}
 
 	return nested_vmx_succeed(vcpu);
-- 
2.19.1


^ permalink raw reply related	[flat|nested] 12+ messages in thread

end of thread, other threads:[~2020-02-04  1:06 UTC | newest]

Thread overview: 12+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2020-01-23  9:36 [PATCH] KVM: nVMX: set rflags to specify success in handle_invvpid() default case linmiaohe
  -- strict thread matches above, loose matches on Subject: below --
2020-02-04  1:06 linmiaohe
2020-02-03  3:29 linmiaohe
2020-02-03  9:48 ` Vitaly Kuznetsov
2020-01-23  3:14 linmiaohe
2020-01-23  8:55 ` Vitaly Kuznetsov
2020-01-23  9:23   ` Paolo Bonzini
2020-01-23  9:45     ` Vitaly Kuznetsov
2020-01-23  9:54       ` Paolo Bonzini
2020-01-23 18:22         ` Jim Mattson
2020-01-23 23:01           ` Sean Christopherson
2020-01-24 10:53             ` Vitaly Kuznetsov

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