RE: [PATCH v6 2/5] KVM: x86: Add IBPB support

> From: Paolo Bonzini > Sent: Thursday, May 3, 2018 5:20 PM > > On 03/05/2018 03:27, Wanpeng Li wrote: > > So for 1) guest->guest attacks 2) guest/ring3->host/ring3 attacks 3) > > guest/ring0->host/ring0 attacks, if IBPB is enough to protect these > > three scenarios and retpoline is not needed?

RE: [PATCH v6 2/5] KVM: x86: Add IBPB support

> From: Paolo Bonzini > Sent: Thursday, May 3, 2018 5:20 PM > > On 03/05/2018 03:27, Wanpeng Li wrote: > > So for 1) guest->guest attacks 2) guest/ring3->host/ring3 attacks 3) > > guest/ring0->host/ring0 attacks, if IBPB is enough to protect these > > three scenarios and retpoline is not needed?

Re: [PATCH v6 2/5] KVM: x86: Add IBPB support

2018-05-03 17:19 GMT+08:00 Paolo Bonzini : > On 03/05/2018 03:27, Wanpeng Li wrote: >> So for 1) guest->guest attacks 2) guest/ring3->host/ring3 attacks 3) >> guest/ring0->host/ring0 attacks, if IBPB is enough to protect these >> three scenarios and retpoline is not needed? >

Re: [PATCH v6 2/5] KVM: x86: Add IBPB support

2018-05-03 17:19 GMT+08:00 Paolo Bonzini : > On 03/05/2018 03:27, Wanpeng Li wrote: >> So for 1) guest->guest attacks 2) guest/ring3->host/ring3 attacks 3) >> guest/ring0->host/ring0 attacks, if IBPB is enough to protect these >> three scenarios and retpoline is not needed? > > In theory yes, in

Re: [PATCH v6 2/5] KVM: x86: Add IBPB support

On 03/05/2018 03:27, Wanpeng Li wrote: > So for 1) guest->guest attacks 2) guest/ring3->host/ring3 attacks 3) > guest/ring0->host/ring0 attacks, if IBPB is enough to protect these > three scenarios and retpoline is not needed? In theory yes, in practice if you want to do that IBPB is much more

Re: [PATCH v6 2/5] KVM: x86: Add IBPB support

On 03/05/2018 03:27, Wanpeng Li wrote: > So for 1) guest->guest attacks 2) guest/ring3->host/ring3 attacks 3) > guest/ring0->host/ring0 attacks, if IBPB is enough to protect these > three scenarios and retpoline is not needed? In theory yes, in practice if you want to do that IBPB is much more

Re: [PATCH v6 2/5] KVM: x86: Add IBPB support

Hi Ashok， 2018-02-02 5:59 GMT+08:00 KarimAllah Ahmed : > From: Ashok Raj > > The Indirect Branch Predictor Barrier (IBPB) is an indirect branch > control mechanism. It keeps earlier branches from influencing > later ones. > > Unlike IBRS and STIBP, IBPB

Re: [PATCH v6 2/5] KVM: x86: Add IBPB support

Hi Ashok， 2018-02-02 5:59 GMT+08:00 KarimAllah Ahmed : > From: Ashok Raj > > The Indirect Branch Predictor Barrier (IBPB) is an indirect branch > control mechanism. It keeps earlier branches from influencing > later ones. > > Unlike IBRS and STIBP, IBPB does not define a new mode of operation. >

Re: [PATCH v6 2/5] KVM: x86: Add IBPB support

> > + wrmsrl(MSR_IA32_PRED_CMD, PRED_CMD_IBPB); > > Should this be wrmsrl_safe? I don't see where we've verified host > support of this MSR. In mainline all wrmsr are wrmsrl_safe now. -Andi

Re: [PATCH v6 2/5] KVM: x86: Add IBPB support

> > + wrmsrl(MSR_IA32_PRED_CMD, PRED_CMD_IBPB); > > Should this be wrmsrl_safe? I don't see where we've verified host > support of this MSR. In mainline all wrmsr are wrmsrl_safe now. -Andi

Re: [PATCH v6 2/5] KVM: x86: Add IBPB support

On Thu, Feb 1, 2018 at 1:59 PM, KarimAllah Ahmed wrote: > @@ -3684,6 +3696,22 @@ static int svm_set_msr(struct kvm_vcpu *vcpu, struct > msr_data *msr) > case MSR_IA32_TSC: > kvm_write_tsc(vcpu, msr); > break; > + case

Re: [PATCH v6 2/5] KVM: x86: Add IBPB support

On Thu, Feb 1, 2018 at 1:59 PM, KarimAllah Ahmed wrote: > @@ -3684,6 +3696,22 @@ static int svm_set_msr(struct kvm_vcpu *vcpu, struct > msr_data *msr) > case MSR_IA32_TSC: > kvm_write_tsc(vcpu, msr); > break; > + case MSR_IA32_PRED_CMD: > +

Re: [PATCH v6 2/5] KVM: x86: Add IBPB support

On 02/02/2018 21:28, Konrad Rzeszutek Wilk wrote: Nothing would *set* the IBPB bit though, since that's a "virtual" bit on Intel hardware. The comment explains why we have that |= F(IBPB), and if the comment wasn't true, we wouldn't need that code either. >>> But this seems wrong.

Re: [PATCH v6 2/5] KVM: x86: Add IBPB support

On 02/02/2018 21:28, Konrad Rzeszutek Wilk wrote: Nothing would *set* the IBPB bit though, since that's a "virtual" bit on Intel hardware. The comment explains why we have that |= F(IBPB), and if the comment wasn't true, we wouldn't need that code either. >>> But this seems wrong.

Re: [PATCH v6 2/5] KVM: x86: Add IBPB support

On 02/02/2018 21:52, Alan Cox wrote: >>> No. The AMD feature bits give us more fine-grained support for exposing >>> IBPB or IBRS alone, so we expose those bits on Intel too. >> But but.. that runs smack against the idea of exposing a platform that >> is as close to emulating the real hardware

Re: [PATCH v6 2/5] KVM: x86: Add IBPB support

On 02/02/2018 21:52, Alan Cox wrote: >>> No. The AMD feature bits give us more fine-grained support for exposing >>> IBPB or IBRS alone, so we expose those bits on Intel too. >> But but.. that runs smack against the idea of exposing a platform that >> is as close to emulating the real hardware

Re: [PATCH v6 2/5] KVM: x86: Add IBPB support

On Fri, Feb 02, 2018 at 08:31:27PM +, David Woodhouse wrote: > On Fri, 2018-02-02 at 15:28 -0500, Konrad Rzeszutek Wilk wrote: > > > > >  > > > No. The AMD feature bits give us more fine-grained support for exposing > > > IBPB or IBRS alone, so we expose those bits on Intel too. > > > > But

Re: [PATCH v6 2/5] KVM: x86: Add IBPB support

On Fri, Feb 02, 2018 at 08:31:27PM +, David Woodhouse wrote: > On Fri, 2018-02-02 at 15:28 -0500, Konrad Rzeszutek Wilk wrote: > > > > >  > > > No. The AMD feature bits give us more fine-grained support for exposing > > > IBPB or IBRS alone, so we expose those bits on Intel too. > > > > But

Re: [PATCH v6 2/5] KVM: x86: Add IBPB support

> > No. The AMD feature bits give us more fine-grained support for exposing > > IBPB or IBRS alone, so we expose those bits on Intel too. > > But but.. that runs smack against the idea of exposing a platform that > is as close to emulating the real hardware as possible. Agreed, and it's asking

Re: [PATCH v6 2/5] KVM: x86: Add IBPB support

> > No. The AMD feature bits give us more fine-grained support for exposing > > IBPB or IBRS alone, so we expose those bits on Intel too. > > But but.. that runs smack against the idea of exposing a platform that > is as close to emulating the real hardware as possible. Agreed, and it's asking

Re: [PATCH v6 2/5] KVM: x86: Add IBPB support

On Fri, 2018-02-02 at 15:28 -0500, Konrad Rzeszutek Wilk wrote: > > >  > > No. The AMD feature bits give us more fine-grained support for exposing > > IBPB or IBRS alone, so we expose those bits on Intel too. > > But but.. that runs smack against the idea of exposing a platform that > is as

Re: [PATCH v6 2/5] KVM: x86: Add IBPB support

On Fri, 2018-02-02 at 15:28 -0500, Konrad Rzeszutek Wilk wrote: > > >  > > No. The AMD feature bits give us more fine-grained support for exposing > > IBPB or IBRS alone, so we expose those bits on Intel too. > > But but.. that runs smack against the idea of exposing a platform that > is as

Re: [PATCH v6 2/5] KVM: x86: Add IBPB support

On Fri, Feb 02, 2018 at 08:16:15PM +, David Woodhouse wrote: > > > On Fri, 2018-02-02 at 14:56 -0500, Konrad Rzeszutek Wilk wrote: > > On Fri, Feb 02, 2018 at 06:02:24PM +, David Woodhouse wrote: > > > > > > On Fri, 2018-02-02 at 12:49 -0500, Konrad Rzeszutek Wilk wrote: > > > > > > >

Re: [PATCH v6 2/5] KVM: x86: Add IBPB support

On Fri, Feb 02, 2018 at 08:16:15PM +, David Woodhouse wrote: > > > On Fri, 2018-02-02 at 14:56 -0500, Konrad Rzeszutek Wilk wrote: > > On Fri, Feb 02, 2018 at 06:02:24PM +, David Woodhouse wrote: > > > > > > On Fri, 2018-02-02 at 12:49 -0500, Konrad Rzeszutek Wilk wrote: > > > > > > >

Re: [PATCH v6 2/5] KVM: x86: Add IBPB support

On Fri, 2018-02-02 at 14:56 -0500, Konrad Rzeszutek Wilk wrote: > On Fri, Feb 02, 2018 at 06:02:24PM +, David Woodhouse wrote: > > > > On Fri, 2018-02-02 at 12:49 -0500, Konrad Rzeszutek Wilk wrote: > > > > > > > > > > > @@ -625,7 +629,12 @@ static inline int __do_cpuid_ent(struct > > > >

Re: [PATCH v6 2/5] KVM: x86: Add IBPB support

On Fri, 2018-02-02 at 14:56 -0500, Konrad Rzeszutek Wilk wrote: > On Fri, Feb 02, 2018 at 06:02:24PM +, David Woodhouse wrote: > > > > On Fri, 2018-02-02 at 12:49 -0500, Konrad Rzeszutek Wilk wrote: > > > > > > > > > > > @@ -625,7 +629,12 @@ static inline int __do_cpuid_ent(struct > > > >

Re: [PATCH v6 2/5] KVM: x86: Add IBPB support

On Fri, Feb 02, 2018 at 06:02:24PM +, David Woodhouse wrote: > On Fri, 2018-02-02 at 12:49 -0500, Konrad Rzeszutek Wilk wrote: > > > @@ -625,7 +629,12 @@ static inline int __do_cpuid_ent(struct > > > kvm_cpuid_entry2 *entry, u32 function, > > > if (!g_phys_as) > > > 

Re: [PATCH v6 2/5] KVM: x86: Add IBPB support

On Fri, Feb 02, 2018 at 06:02:24PM +, David Woodhouse wrote: > On Fri, 2018-02-02 at 12:49 -0500, Konrad Rzeszutek Wilk wrote: > > > @@ -625,7 +629,12 @@ static inline int __do_cpuid_ent(struct > > > kvm_cpuid_entry2 *entry, u32 function, > > > if (!g_phys_as) > > > 

Re: [PATCH v6 2/5] KVM: x86: Add IBPB support

On Fri, 2018-02-02 at 12:49 -0500, Konrad Rzeszutek Wilk wrote: > > @@ -625,7 +629,12 @@ static inline int __do_cpuid_ent(struct > > kvm_cpuid_entry2 *entry, u32 function, > > if (!g_phys_as) > > g_phys_as = phys_as; > > entry->eax =

Re: [PATCH v6 2/5] KVM: x86: Add IBPB support

On Fri, 2018-02-02 at 12:49 -0500, Konrad Rzeszutek Wilk wrote: > > @@ -625,7 +629,12 @@ static inline int __do_cpuid_ent(struct > > kvm_cpuid_entry2 *entry, u32 function, > > if (!g_phys_as) > > g_phys_as = phys_as; > > entry->eax =

Re: [PATCH v6 2/5] KVM: x86: Add IBPB support

On Thu, Feb 01, 2018 at 10:59:43PM +0100, KarimAllah Ahmed wrote: > From: Ashok Raj > > The Indirect Branch Predictor Barrier (IBPB) is an indirect branch > control mechanism. It keeps earlier branches from influencing > later ones. > > Unlike IBRS and STIBP, IBPB does not

Re: [PATCH v6 2/5] KVM: x86: Add IBPB support

On Thu, Feb 01, 2018 at 10:59:43PM +0100, KarimAllah Ahmed wrote: > From: Ashok Raj > > The Indirect Branch Predictor Barrier (IBPB) is an indirect branch > control mechanism. It keeps earlier branches from influencing > later ones. > > Unlike IBRS and STIBP, IBPB does not define a new mode of

[PATCH v6 2/5] KVM: x86: Add IBPB support

From: Ashok Raj The Indirect Branch Predictor Barrier (IBPB) is an indirect branch control mechanism. It keeps earlier branches from influencing later ones. Unlike IBRS and STIBP, IBPB does not define a new mode of operation. It's a command that ensures predicted branch

[PATCH v6 2/5] KVM: x86: Add IBPB support

From: Ashok Raj The Indirect Branch Predictor Barrier (IBPB) is an indirect branch control mechanism. It keeps earlier branches from influencing later ones. Unlike IBRS and STIBP, IBPB does not define a new mode of operation. It's a command that ensures predicted branch targets aren't used