On Tue, Aug 25, 2020 at 02:53:47PM +0100, Marc Zyngier wrote:
On 2020-08-25 11:54, Catalin Marinas wrote:
> On Tue, Aug 25, 2020 at 09:53:16AM +0100, Marc Zyngier wrote:
> > On 2020-08-24 19:27, Catalin Marinas wrote:
> > > diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
> > > index 077293b5115f..59b91f58efec 100644
> > > --- a/arch/arm64/kvm/sys_regs.c
> > > +++ b/arch/arm64/kvm/sys_regs.c
> > > @@ -1131,6 +1131,8 @@ static u64 read_id_reg(const struct kvm_vcpu
> > > *vcpu,
> > > if (!vcpu_has_sve(vcpu))
> > > val &= ~(0xfUL << ID_AA64PFR0_SVE_SHIFT);
> > > val &= ~(0xfUL << ID_AA64PFR0_AMU_SHIFT);
> > > + } else if (id == SYS_ID_AA64PFR1_EL1) {
> > > + val &= ~(0xfUL << ID_AA64PFR1_MTE_SHIFT);
> >
> > Hiding the capability is fine, but where is the handling of trapping
> > instructions done? They should result in an UNDEF being injected.
>
> They are a few new MTE-specific MSR/MRS which are trapped at EL2 but
> since KVM doesn't understand them yet, shouldn't it already inject
> undef back at EL1? That would be safer regardless of MTE support.
An UNDEF will be injected, but not without spitting a nastygram in
the kernel log (look at emulate_sys_reg()).
The best course of action is to have an entry in the sysreg table
that would explicitly do the handling.
Something like below. I'll put them in a separate patch, to be reverted
when we get proper MTE support in KVM.
diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index 59b91f58efec..c7d5d1bae044 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -1384,6 +1384,13 @@ static bool access_ccsidr(struct kvm_vcpu
*vcpu, struct sys_reg_params *p,
return true;
}
+static bool access_mte_regs(struct kvm_vcpu *vcpu, struct
sys_reg_params *p,
+ const struct sys_reg_desc *r)
+{
+ kvm_inject_undefined(vcpu);
+ return false;
+}
+
/* sys_reg_desc initialiser for known cpufeature ID registers */
#define ID_SANITISED(name) { \
SYS_DESC(SYS_##name), \
@@ -1549,6 +1556,10 @@ static const struct sys_reg_desc sys_reg_descs[]
= {
{ SYS_DESC(SYS_SCTLR_EL1), access_vm_reg, reset_val, SCTLR_EL1,
0x00C50078 },
{ SYS_DESC(SYS_ACTLR_EL1), access_actlr, reset_actlr, ACTLR_EL1 },
{ SYS_DESC(SYS_CPACR_EL1), NULL, reset_val, CPACR_EL1, 0 },
+
+ { SYS_DESC(SYS_RGSR_EL1), access_mte_regs },
+ { SYS_DESC(SYS_GCR_EL1), access_mte_regs },
+
{ SYS_DESC(SYS_ZCR_EL1), NULL, reset_val, ZCR_EL1, 0, .visibility =
sve_visibility },
{ SYS_DESC(SYS_TTBR0_EL1), access_vm_reg, reset_unknown, TTBR0_EL1 },
{ SYS_DESC(SYS_TTBR1_EL1), access_vm_reg, reset_unknown, TTBR1_EL1 },
@@ -1573,6 +1584,9 @@ static const struct sys_reg_desc sys_reg_descs[]
= {
{ SYS_DESC(SYS_ERXMISC0_EL1), trap_raz_wi },
{ SYS_DESC(SYS_ERXMISC1_EL1), trap_raz_wi },
+ { SYS_DESC(SYS_TFSR_EL1), access_mte_regs },
+ { SYS_DESC(SYS_TFSRE0_EL1), access_mte_regs },
+
{ SYS_DESC(SYS_FAR_EL1), access_vm_reg, reset_unknown, FAR_EL1 },
{ SYS_DESC(SYS_PAR_EL1), NULL, reset_unknown, PAR_EL1 },
