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* [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
* 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
@ 2020-02-03  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
@ 2020-02-04  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

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  3:14 [PATCH] KVM: nVMX: set rflags to specify success in handle_invvpid() default case 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
2020-01-23  9:36 linmiaohe
2020-02-03  3:29 linmiaohe
2020-02-03  9:48 ` Vitaly Kuznetsov
2020-02-04  1:06 linmiaohe

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