Wire up the other end of traps that affect host EL0 by actually
injecting them into the guest hypervisor. Skip over FGT entirely, as a
cursory glance suggests no FGT is effective in host EL0.
Note that kvm_inject_nested() is already equipped for handling
exceptions while the VM is already in a host context.
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
---
arch/arm64/include/asm/kvm_emulate.h | 5 +++++
arch/arm64/kvm/emulate-nested.c | 29 ++++++++++++++++++++++++----
2 files changed, 30 insertions(+), 4 deletions(-)
diff --git a/arch/arm64/include/asm/kvm_emulate.h b/arch/arm64/include/asm/kvm_emulate.h
index a601a9305b10..bf0c48403f59 100644
--- a/arch/arm64/include/asm/kvm_emulate.h
+++ b/arch/arm64/include/asm/kvm_emulate.h
@@ -225,6 +225,11 @@ static inline bool is_hyp_ctxt(const struct kvm_vcpu *vcpu)
return vcpu_has_nv(vcpu) && __is_hyp_ctxt(&vcpu->arch.ctxt);
}
+static inline bool vcpu_is_host_el0(const struct kvm_vcpu *vcpu)
+{
+ return is_hyp_ctxt(vcpu) && !vcpu_is_el2(vcpu);
+}
+
/*
* The layout of SPSR for an AArch32 state is different when observed from an
* AArch64 SPSR_ELx or an AArch32 SPSR_*. This function generates the AArch32
diff --git a/arch/arm64/kvm/emulate-nested.c b/arch/arm64/kvm/emulate-nested.c
index e1a30d1bcd06..db3149379a4d 100644
--- a/arch/arm64/kvm/emulate-nested.c
+++ b/arch/arm64/kvm/emulate-nested.c
@@ -20,6 +20,9 @@ enum trap_behaviour {
BEHAVE_FORWARD_READ = BIT(0),
BEHAVE_FORWARD_WRITE = BIT(1),
BEHAVE_FORWARD_RW = BEHAVE_FORWARD_READ | BEHAVE_FORWARD_WRITE,
+
+ /* Traps that take effect in Host EL0, this is rare! */
+ BEHAVE_IN_HOST_EL0 = BIT(2),
};
struct trap_bits {
@@ -2128,11 +2131,19 @@ static u64 kvm_get_sysreg_res0(struct kvm *kvm, enum vcpu_sysreg sr)
return masks->mask[sr - __VNCR_START__].res0;
}
-static bool check_fgt_bit(struct kvm *kvm, bool is_read,
+static bool check_fgt_bit(struct kvm_vcpu *vcpu, bool is_read,
u64 val, const union trap_config tc)
{
+ struct kvm *kvm = vcpu->kvm;
enum vcpu_sysreg sr;
+ /*
+ * KVM doesn't know about any FGTs that apply to the host, and hopefully
+ * that'll remain the case.
+ */
+ if (is_hyp_ctxt(vcpu))
+ return false;
+
if (tc.pol)
return (val & BIT(tc.bit));
@@ -2209,7 +2220,15 @@ bool triage_sysreg_trap(struct kvm_vcpu *vcpu, int *sr_index)
* If we're not nesting, immediately return to the caller, with the
* sysreg index, should we have it.
*/
- if (!vcpu_has_nv(vcpu) || is_hyp_ctxt(vcpu))
+ if (!vcpu_has_nv(vcpu))
+ goto local;
+
+ /*
+ * There are a few traps that take effect InHost, but are constrained
+ * to EL0. Don't bother with computing the trap behaviour if the vCPU
+ * isn't in EL0.
+ */
+ if (is_hyp_ctxt(vcpu) && !vcpu_is_host_el0(vcpu))
goto local;
switch ((enum fgt_group_id)tc.fgt) {
@@ -2255,12 +2274,14 @@ bool triage_sysreg_trap(struct kvm_vcpu *vcpu, int *sr_index)
goto local;
}
- if (tc.fgt != __NO_FGT_GROUP__ && check_fgt_bit(vcpu->kvm, is_read,
- val, tc))
+ if (tc.fgt != __NO_FGT_GROUP__ && check_fgt_bit(vcpu, is_read, val, tc))
goto inject;
b = compute_trap_behaviour(vcpu, tc);
+ if (!(b & BEHAVE_IN_HOST_EL0) && vcpu_is_host_el0(vcpu))
+ goto local;
+
if (((b & BEHAVE_FORWARD_READ) && is_read) ||
((b & BEHAVE_FORWARD_WRITE) && !is_read))
goto inject;
--
2.47.0.163.g1226f6d8fa-googOn Fri, 25 Oct 2024 19:23:43 +0100,
Oliver Upton <oliver.upton@linux.dev> wrote:
>
> Wire up the other end of traps that affect host EL0 by actually
> injecting them into the guest hypervisor. Skip over FGT entirely, as a
> cursory glance suggests no FGT is effective in host EL0.
Yes, and this (thankfully) is by design! :-)
>
> Note that kvm_inject_nested() is already equipped for handling
> exceptions while the VM is already in a host context.
>
> Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
> ---
> arch/arm64/include/asm/kvm_emulate.h | 5 +++++
> arch/arm64/kvm/emulate-nested.c | 29 ++++++++++++++++++++++++----
> 2 files changed, 30 insertions(+), 4 deletions(-)
>
> diff --git a/arch/arm64/include/asm/kvm_emulate.h b/arch/arm64/include/asm/kvm_emulate.h
> index a601a9305b10..bf0c48403f59 100644
> --- a/arch/arm64/include/asm/kvm_emulate.h
> +++ b/arch/arm64/include/asm/kvm_emulate.h
> @@ -225,6 +225,11 @@ static inline bool is_hyp_ctxt(const struct kvm_vcpu *vcpu)
> return vcpu_has_nv(vcpu) && __is_hyp_ctxt(&vcpu->arch.ctxt);
> }
>
> +static inline bool vcpu_is_host_el0(const struct kvm_vcpu *vcpu)
> +{
> + return is_hyp_ctxt(vcpu) && !vcpu_is_el2(vcpu);
> +}
> +
> /*
> * The layout of SPSR for an AArch32 state is different when observed from an
> * AArch64 SPSR_ELx or an AArch32 SPSR_*. This function generates the AArch32
> diff --git a/arch/arm64/kvm/emulate-nested.c b/arch/arm64/kvm/emulate-nested.c
> index e1a30d1bcd06..db3149379a4d 100644
> --- a/arch/arm64/kvm/emulate-nested.c
> +++ b/arch/arm64/kvm/emulate-nested.c
> @@ -20,6 +20,9 @@ enum trap_behaviour {
> BEHAVE_FORWARD_READ = BIT(0),
> BEHAVE_FORWARD_WRITE = BIT(1),
> BEHAVE_FORWARD_RW = BEHAVE_FORWARD_READ | BEHAVE_FORWARD_WRITE,
> +
> + /* Traps that take effect in Host EL0, this is rare! */
> + BEHAVE_IN_HOST_EL0 = BIT(2),
nit: BEHAVE_IN_HOST_EL0 lacks an action verb (forward?).
Thanks,
M.
--
Without deviation from the norm, progress is not possible.
Hey,
On Sat, Oct 26, 2024 at 09:13:17AM +0100, Marc Zyngier wrote:
> On Fri, 25 Oct 2024 19:23:43 +0100,
> Oliver Upton <oliver.upton@linux.dev> wrote:
> >
> > Wire up the other end of traps that affect host EL0 by actually
> > injecting them into the guest hypervisor. Skip over FGT entirely, as a
> > cursory glance suggests no FGT is effective in host EL0.
>
> Yes, and this (thankfully) is by design! :-)
>
> >
> > Note that kvm_inject_nested() is already equipped for handling
> > exceptions while the VM is already in a host context.
> >
> > Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
> > ---
> > arch/arm64/include/asm/kvm_emulate.h | 5 +++++
> > arch/arm64/kvm/emulate-nested.c | 29 ++++++++++++++++++++++++----
> > 2 files changed, 30 insertions(+), 4 deletions(-)
> >
> > diff --git a/arch/arm64/include/asm/kvm_emulate.h b/arch/arm64/include/asm/kvm_emulate.h
> > index a601a9305b10..bf0c48403f59 100644
> > --- a/arch/arm64/include/asm/kvm_emulate.h
> > +++ b/arch/arm64/include/asm/kvm_emulate.h
> > @@ -225,6 +225,11 @@ static inline bool is_hyp_ctxt(const struct kvm_vcpu *vcpu)
> > return vcpu_has_nv(vcpu) && __is_hyp_ctxt(&vcpu->arch.ctxt);
> > }
> >
> > +static inline bool vcpu_is_host_el0(const struct kvm_vcpu *vcpu)
> > +{
> > + return is_hyp_ctxt(vcpu) && !vcpu_is_el2(vcpu);
> > +}
> > +
> > /*
> > * The layout of SPSR for an AArch32 state is different when observed from an
> > * AArch64 SPSR_ELx or an AArch32 SPSR_*. This function generates the AArch32
> > diff --git a/arch/arm64/kvm/emulate-nested.c b/arch/arm64/kvm/emulate-nested.c
> > index e1a30d1bcd06..db3149379a4d 100644
> > --- a/arch/arm64/kvm/emulate-nested.c
> > +++ b/arch/arm64/kvm/emulate-nested.c
> > @@ -20,6 +20,9 @@ enum trap_behaviour {
> > BEHAVE_FORWARD_READ = BIT(0),
> > BEHAVE_FORWARD_WRITE = BIT(1),
> > BEHAVE_FORWARD_RW = BEHAVE_FORWARD_READ | BEHAVE_FORWARD_WRITE,
> > +
> > + /* Traps that take effect in Host EL0, this is rare! */
> > + BEHAVE_IN_HOST_EL0 = BIT(2),
>
> nit: BEHAVE_IN_HOST_EL0 lacks an action verb (forward?).
Thinking I'll squash this in (plus renaming in later patches):
diff --git a/arch/arm64/kvm/emulate-nested.c b/arch/arm64/kvm/emulate-nested.c
index db3149379a4d..b072098ee44e 100644
--- a/arch/arm64/kvm/emulate-nested.c
+++ b/arch/arm64/kvm/emulate-nested.c
@@ -22,7 +22,7 @@ enum trap_behaviour {
BEHAVE_FORWARD_RW = BEHAVE_FORWARD_READ | BEHAVE_FORWARD_WRITE,
/* Traps that take effect in Host EL0, this is rare! */
- BEHAVE_IN_HOST_EL0 = BIT(2),
+ BEHAVE_FORWARD_IN_HOST_EL0 = BIT(2),
};
struct trap_bits {
@@ -2279,7 +2279,7 @@ bool triage_sysreg_trap(struct kvm_vcpu *vcpu, int *sr_index)
b = compute_trap_behaviour(vcpu, tc);
- if (!(b & BEHAVE_IN_HOST_EL0) && vcpu_is_host_el0(vcpu))
+ if (!(b & BEHAVE_FORWARD_IN_HOST_EL0) && vcpu_is_host_el0(vcpu))
goto local;
if (((b & BEHAVE_FORWARD_READ) && is_read) ||
--
Thanks,
Oliver
On 10/26/24 20:05, Oliver Upton wrote:
> Hey,
>
> On Sat, Oct 26, 2024 at 09:13:17AM +0100, Marc Zyngier wrote:
>> On Fri, 25 Oct 2024 19:23:43 +0100,
>> Oliver Upton <oliver.upton@linux.dev> wrote:
>>>
>>> Wire up the other end of traps that affect host EL0 by actually
>>> injecting them into the guest hypervisor. Skip over FGT entirely, as a
>>> cursory glance suggests no FGT is effective in host EL0.
>>
>> Yes, and this (thankfully) is by design! :-)
>>
>>>
>>> Note that kvm_inject_nested() is already equipped for handling
>>> exceptions while the VM is already in a host context.
>>>
>>> Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
>>> ---
>>> arch/arm64/include/asm/kvm_emulate.h | 5 +++++
>>> arch/arm64/kvm/emulate-nested.c | 29 ++++++++++++++++++++++++----
>>> 2 files changed, 30 insertions(+), 4 deletions(-)
>>>
>>> diff --git a/arch/arm64/include/asm/kvm_emulate.h b/arch/arm64/include/asm/kvm_emulate.h
>>> index a601a9305b10..bf0c48403f59 100644
>>> --- a/arch/arm64/include/asm/kvm_emulate.h
>>> +++ b/arch/arm64/include/asm/kvm_emulate.h
>>> @@ -225,6 +225,11 @@ static inline bool is_hyp_ctxt(const struct kvm_vcpu *vcpu)
>>> return vcpu_has_nv(vcpu) && __is_hyp_ctxt(&vcpu->arch.ctxt);
>>> }
>>>
>>> +static inline bool vcpu_is_host_el0(const struct kvm_vcpu *vcpu)
>>> +{
>>> + return is_hyp_ctxt(vcpu) && !vcpu_is_el2(vcpu);
>>> +}
>>> +
>>> /*
>>> * The layout of SPSR for an AArch32 state is different when observed from an
>>> * AArch64 SPSR_ELx or an AArch32 SPSR_*. This function generates the AArch32
>>> diff --git a/arch/arm64/kvm/emulate-nested.c b/arch/arm64/kvm/emulate-nested.c
>>> index e1a30d1bcd06..db3149379a4d 100644
>>> --- a/arch/arm64/kvm/emulate-nested.c
>>> +++ b/arch/arm64/kvm/emulate-nested.c
>>> @@ -20,6 +20,9 @@ enum trap_behaviour {
>>> BEHAVE_FORWARD_READ = BIT(0),
>>> BEHAVE_FORWARD_WRITE = BIT(1),
>>> BEHAVE_FORWARD_RW = BEHAVE_FORWARD_READ | BEHAVE_FORWARD_WRITE,
>>> +
>>> + /* Traps that take effect in Host EL0, this is rare! */
>>> + BEHAVE_IN_HOST_EL0 = BIT(2),
>>
>> nit: BEHAVE_IN_HOST_EL0 lacks an action verb (forward?).
>
> Thinking I'll squash this in (plus renaming in later patches):
Right, the following additional replacements are required for build.
@@ -307,14 +307,14 @@ static const struct trap_bits coarse_trap_bits[] = {
.value = MDCR_EL2_TPMCR,
.mask = MDCR_EL2_TPMCR,
.behaviour = BEHAVE_FORWARD_RW |
- BEHAVE_IN_HOST_EL0,
+ BEHAVE_FORWARD_IN_HOST_EL0,
},
[CGT_MDCR_TPM] = {
.index = MDCR_EL2,
.value = MDCR_EL2_TPM,
.mask = MDCR_EL2_TPM,
.behaviour = BEHAVE_FORWARD_RW |
- BEHAVE_IN_HOST_EL0,
+ BEHAVE_FORWARD_IN_HOST_EL0,
},
[CGT_MDCR_TDE] = {
.index = MDCR_EL2,
@@ -530,7 +530,7 @@ static enum trap_behaviour check_mdcr_hpmn(struct kvm_vcpu *vcpu)
}
if (kvm_pmu_counter_is_hyp(vcpu, idx))
- return BEHAVE_FORWARD_RW | BEHAVE_IN_HOST_EL0;
+ return BEHAVE_FORWARD_RW | BEHAVE_FORWARD_IN_HOST_EL0;
return BEHAVE_HANDLE_LOCALLY;
}
>
> diff --git a/arch/arm64/kvm/emulate-nested.c b/arch/arm64/kvm/emulate-nested.c
> index db3149379a4d..b072098ee44e 100644
> --- a/arch/arm64/kvm/emulate-nested.c
> +++ b/arch/arm64/kvm/emulate-nested.c
> @@ -22,7 +22,7 @@ enum trap_behaviour {
> BEHAVE_FORWARD_RW = BEHAVE_FORWARD_READ | BEHAVE_FORWARD_WRITE,
>
> /* Traps that take effect in Host EL0, this is rare! */
> - BEHAVE_IN_HOST_EL0 = BIT(2),
> + BEHAVE_FORWARD_IN_HOST_EL0 = BIT(2),
> };
>
> struct trap_bits {
> @@ -2279,7 +2279,7 @@ bool triage_sysreg_trap(struct kvm_vcpu *vcpu, int *sr_index)
>
> b = compute_trap_behaviour(vcpu, tc);
>
> - if (!(b & BEHAVE_IN_HOST_EL0) && vcpu_is_host_el0(vcpu))
> + if (!(b & BEHAVE_FORWARD_IN_HOST_EL0) && vcpu_is_host_el0(vcpu))
> goto local;
>
> if (((b & BEHAVE_FORWARD_READ) && is_read) ||
>
© 2016 - 2026 Red Hat, Inc.