diff mbox series

[v2,10/18] arm64: KVM/debug: use EL1&0 stage 1 translation regime

Message ID 20191220143025.33853-11-andrew.murray@arm.com (mailing list archive)
State New, archived
Headers show
Series arm64: KVM: add SPE profiling support | expand

Commit Message

Andrew Murray Dec. 20, 2019, 2:30 p.m. UTC 
From: Sudeep Holla <sudeep.holla@arm.com>

Now that we have all the save/restore mechanism in place, lets enable
the translation regime used by buffer from EL2 stage 1 to EL1 stage 1
on VHE systems.

Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
[ Reword commit, don't trap to EL2 ]
Signed-off-by: Andrew Murray <andrew.murray@arm.com>
---
 arch/arm64/kvm/hyp/switch.c | 2 ++
 1 file changed, 2 insertions(+)

Comments

Marc Zyngier Dec. 22, 2019, 10:34 a.m. UTC | #1 
On Fri, 20 Dec 2019 14:30:17 +0000,
Andrew Murray <andrew.murray@arm.com> wrote:
> 
> From: Sudeep Holla <sudeep.holla@arm.com>
> 
> Now that we have all the save/restore mechanism in place, lets enable
> the translation regime used by buffer from EL2 stage 1 to EL1 stage 1
> on VHE systems.
> 
> Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
> [ Reword commit, don't trap to EL2 ]

Not trapping to EL2 for the case where we don't allow SPE in the
guest is not acceptable.

> Signed-off-by: Andrew Murray <andrew.murray@arm.com>
> ---
>  arch/arm64/kvm/hyp/switch.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/arch/arm64/kvm/hyp/switch.c b/arch/arm64/kvm/hyp/switch.c
> index 67b7c160f65b..6c153b79829b 100644
> --- a/arch/arm64/kvm/hyp/switch.c
> +++ b/arch/arm64/kvm/hyp/switch.c
> @@ -100,6 +100,7 @@ static void activate_traps_vhe(struct kvm_vcpu *vcpu)
>  
>  	write_sysreg(val, cpacr_el1);
>  
> +	write_sysreg(vcpu->arch.mdcr_el2 | 3 << MDCR_EL2_E2PB_SHIFT, mdcr_el2);
>  	write_sysreg(kvm_get_hyp_vector(), vbar_el1);
>  }
>  NOKPROBE_SYMBOL(activate_traps_vhe);
> @@ -117,6 +118,7 @@ static void __hyp_text __activate_traps_nvhe(struct kvm_vcpu *vcpu)
>  		__activate_traps_fpsimd32(vcpu);
>  	}
>  
> +	write_sysreg(vcpu->arch.mdcr_el2 | 3 << MDCR_EL2_E2PB_SHIFT, mdcr_el2);

There is a _MASK macro that can replace this '3', and is in keeping
with the rest of the code.

It still remains that it looks like the wrong place to do this, and
vcpu_load seems much better. Why should you write to mdcr_el2 on each
entry to the guest, since you know whether it has SPE enabled at the
point where it gets scheduled?

	M.
Andrew Murray Dec. 24, 2019, 11:11 a.m. UTC | #2 
On Sun, Dec 22, 2019 at 10:34:55AM +0000, Marc Zyngier wrote:
> On Fri, 20 Dec 2019 14:30:17 +0000,
> Andrew Murray <andrew.murray@arm.com> wrote:
> > 
> > From: Sudeep Holla <sudeep.holla@arm.com>
> > 
> > Now that we have all the save/restore mechanism in place, lets enable
> > the translation regime used by buffer from EL2 stage 1 to EL1 stage 1
> > on VHE systems.
> > 
> > Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
> > [ Reword commit, don't trap to EL2 ]
> 
> Not trapping to EL2 for the case where we don't allow SPE in the
> guest is not acceptable.

Yes understood (because of this I had meant to send the series as RFC btw).


> 
> > Signed-off-by: Andrew Murray <andrew.murray@arm.com>
> > ---
> >  arch/arm64/kvm/hyp/switch.c | 2 ++
> >  1 file changed, 2 insertions(+)
> > 
> > diff --git a/arch/arm64/kvm/hyp/switch.c b/arch/arm64/kvm/hyp/switch.c
> > index 67b7c160f65b..6c153b79829b 100644
> > --- a/arch/arm64/kvm/hyp/switch.c
> > +++ b/arch/arm64/kvm/hyp/switch.c
> > @@ -100,6 +100,7 @@ static void activate_traps_vhe(struct kvm_vcpu *vcpu)
> >  
> >  	write_sysreg(val, cpacr_el1);
> >  
> > +	write_sysreg(vcpu->arch.mdcr_el2 | 3 << MDCR_EL2_E2PB_SHIFT, mdcr_el2);
> >  	write_sysreg(kvm_get_hyp_vector(), vbar_el1);
> >  }
> >  NOKPROBE_SYMBOL(activate_traps_vhe);
> > @@ -117,6 +118,7 @@ static void __hyp_text __activate_traps_nvhe(struct kvm_vcpu *vcpu)
> >  		__activate_traps_fpsimd32(vcpu);
> >  	}
> >  
> > +	write_sysreg(vcpu->arch.mdcr_el2 | 3 << MDCR_EL2_E2PB_SHIFT, mdcr_el2);
> 
> There is a _MASK macro that can replace this '3', and is in keeping
> with the rest of the code.

OK.


> 
> It still remains that it looks like the wrong place to do this, and
> vcpu_load seems much better. Why should you write to mdcr_el2 on each
> entry to the guest, since you know whether it has SPE enabled at the
> point where it gets scheduled?

Yes OK, I'll move what I can to vcpu_load.

Thanks,

Andrew Murray


> 
> 	M.
> 
> -- 
> Jazz is not dead, it just smells funny.
Andrew Murray Jan. 13, 2020, 4:31 p.m. UTC | #3 
On Sun, Dec 22, 2019 at 10:34:55AM +0000, Marc Zyngier wrote:
> On Fri, 20 Dec 2019 14:30:17 +0000,
> Andrew Murray <andrew.murray@arm.com> wrote:
> > 
> > From: Sudeep Holla <sudeep.holla@arm.com>
> > 
> > Now that we have all the save/restore mechanism in place, lets enable
> > the translation regime used by buffer from EL2 stage 1 to EL1 stage 1
> > on VHE systems.
> > 
> > Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
> > [ Reword commit, don't trap to EL2 ]
> 
> Not trapping to EL2 for the case where we don't allow SPE in the
> guest is not acceptable.
> 
> > Signed-off-by: Andrew Murray <andrew.murray@arm.com>
> > ---
> >  arch/arm64/kvm/hyp/switch.c | 2 ++
> >  1 file changed, 2 insertions(+)
> > 
> > diff --git a/arch/arm64/kvm/hyp/switch.c b/arch/arm64/kvm/hyp/switch.c
> > index 67b7c160f65b..6c153b79829b 100644
> > --- a/arch/arm64/kvm/hyp/switch.c
> > +++ b/arch/arm64/kvm/hyp/switch.c
> > @@ -100,6 +100,7 @@ static void activate_traps_vhe(struct kvm_vcpu *vcpu)
> >  
> >  	write_sysreg(val, cpacr_el1);
> >  
> > +	write_sysreg(vcpu->arch.mdcr_el2 | 3 << MDCR_EL2_E2PB_SHIFT, mdcr_el2);
> >  	write_sysreg(kvm_get_hyp_vector(), vbar_el1);
> >  }
> >  NOKPROBE_SYMBOL(activate_traps_vhe);
> > @@ -117,6 +118,7 @@ static void __hyp_text __activate_traps_nvhe(struct kvm_vcpu *vcpu)
> >  		__activate_traps_fpsimd32(vcpu);
> >  	}
> >  
> > +	write_sysreg(vcpu->arch.mdcr_el2 | 3 << MDCR_EL2_E2PB_SHIFT, mdcr_el2);
> 
> There is a _MASK macro that can replace this '3', and is in keeping
> with the rest of the code.
> 
> It still remains that it looks like the wrong place to do this, and
> vcpu_load seems much better. Why should you write to mdcr_el2 on each
> entry to the guest, since you know whether it has SPE enabled at the
> point where it gets scheduled?

For nVHE, the only reason we'd want to change E2PB on entry/exit of guest
would be if the host is also using SPE. If the host is using SPE whilst
the vcpu is 'loaded' but we're not in the guest, then host SPE could raise
an interrupt - we need the E2PB bits to allow access from EL1 (host).

Thanks,

Andrew Murray

> 
> 	M.
> 
> -- 
> Jazz is not dead, it just smells funny.
Marc Zyngier Jan. 15, 2020, 2:03 p.m. UTC | #4 
On 2020-01-13 16:31, Andrew Murray wrote:
> On Sun, Dec 22, 2019 at 10:34:55AM +0000, Marc Zyngier wrote:
>> On Fri, 20 Dec 2019 14:30:17 +0000,
>> Andrew Murray <andrew.murray@arm.com> wrote:
>> >
>> > From: Sudeep Holla <sudeep.holla@arm.com>
>> >
>> > Now that we have all the save/restore mechanism in place, lets enable
>> > the translation regime used by buffer from EL2 stage 1 to EL1 stage 1
>> > on VHE systems.
>> >
>> > Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
>> > [ Reword commit, don't trap to EL2 ]
>> 
>> Not trapping to EL2 for the case where we don't allow SPE in the
>> guest is not acceptable.
>> 
>> > Signed-off-by: Andrew Murray <andrew.murray@arm.com>
>> > ---
>> >  arch/arm64/kvm/hyp/switch.c | 2 ++
>> >  1 file changed, 2 insertions(+)
>> >
>> > diff --git a/arch/arm64/kvm/hyp/switch.c b/arch/arm64/kvm/hyp/switch.c
>> > index 67b7c160f65b..6c153b79829b 100644
>> > --- a/arch/arm64/kvm/hyp/switch.c
>> > +++ b/arch/arm64/kvm/hyp/switch.c
>> > @@ -100,6 +100,7 @@ static void activate_traps_vhe(struct kvm_vcpu *vcpu)
>> >
>> >  	write_sysreg(val, cpacr_el1);
>> >
>> > +	write_sysreg(vcpu->arch.mdcr_el2 | 3 << MDCR_EL2_E2PB_SHIFT, mdcr_el2);
>> >  	write_sysreg(kvm_get_hyp_vector(), vbar_el1);
>> >  }
>> >  NOKPROBE_SYMBOL(activate_traps_vhe);
>> > @@ -117,6 +118,7 @@ static void __hyp_text __activate_traps_nvhe(struct kvm_vcpu *vcpu)
>> >  		__activate_traps_fpsimd32(vcpu);
>> >  	}
>> >
>> > +	write_sysreg(vcpu->arch.mdcr_el2 | 3 << MDCR_EL2_E2PB_SHIFT, mdcr_el2);
>> 
>> There is a _MASK macro that can replace this '3', and is in keeping
>> with the rest of the code.
>> 
>> It still remains that it looks like the wrong place to do this, and
>> vcpu_load seems much better. Why should you write to mdcr_el2 on each
>> entry to the guest, since you know whether it has SPE enabled at the
>> point where it gets scheduled?
> 
> For nVHE, the only reason we'd want to change E2PB on entry/exit of 
> guest
> would be if the host is also using SPE. If the host is using SPE whilst
> the vcpu is 'loaded' but we're not in the guest, then host SPE could 
> raise
> an interrupt - we need the E2PB bits to allow access from EL1 (host).

My comment was of course for VHE. nVHE hardly makes use of load/put at 
all,
for obvious reasons.

         M.
diff mbox series

Patch

diff --git a/arch/arm64/kvm/hyp/switch.c b/arch/arm64/kvm/hyp/switch.c
index 67b7c160f65b..6c153b79829b 100644
--- a/arch/arm64/kvm/hyp/switch.c
+++ b/arch/arm64/kvm/hyp/switch.c
@@ -100,6 +100,7 @@  static void activate_traps_vhe(struct kvm_vcpu *vcpu)
 
 	write_sysreg(val, cpacr_el1);
 
+	write_sysreg(vcpu->arch.mdcr_el2 | 3 << MDCR_EL2_E2PB_SHIFT, mdcr_el2);
 	write_sysreg(kvm_get_hyp_vector(), vbar_el1);
 }
 NOKPROBE_SYMBOL(activate_traps_vhe);
@@ -117,6 +118,7 @@  static void __hyp_text __activate_traps_nvhe(struct kvm_vcpu *vcpu)
 		__activate_traps_fpsimd32(vcpu);
 	}
 
+	write_sysreg(vcpu->arch.mdcr_el2 | 3 << MDCR_EL2_E2PB_SHIFT, mdcr_el2);
 	write_sysreg(val, cptr_el2);
 
 	if (cpus_have_const_cap(ARM64_WORKAROUND_1319367)) {