Hi Marc, On Fri, Jan 28, 2022 at 12:18:26PM +0000, Marc Zyngier wrote: > From: Christoffer Dall <[email protected]> > > When running in virtual EL2 mode, we actually run the hardware in EL1 > and therefore have to use the EL1 registers to ensure correct operation. > > By setting the HCR.TVM and HCR.TVRM we ensure that the virtual EL2 mode > doesn't shoot itself in the foot when setting up what it believes to be > a different mode's system register state (for example when preparing to > switch to a VM). > > We can leverage the existing sysregs infrastructure to support trapped > accesses to these registers. > > Signed-off-by: Christoffer Dall <[email protected]> > Signed-off-by: Marc Zyngier <[email protected]> > --- > arch/arm64/kvm/hyp/include/hyp/switch.h | 4 +--- > arch/arm64/kvm/hyp/nvhe/switch.c | 2 +- > arch/arm64/kvm/hyp/vhe/switch.c | 7 ++++++- > arch/arm64/kvm/sys_regs.c | 19 ++++++++++++++++--- > 4 files changed, 24 insertions(+), 8 deletions(-) > > diff --git a/arch/arm64/kvm/hyp/include/hyp/switch.h > b/arch/arm64/kvm/hyp/include/hyp/switch.h > index 58e14f8ead23..49c3b9eb09d7 100644 > --- a/arch/arm64/kvm/hyp/include/hyp/switch.h > +++ b/arch/arm64/kvm/hyp/include/hyp/switch.h > @@ -110,10 +110,8 @@ static inline void __deactivate_traps_common(struct > kvm_vcpu *vcpu) > write_sysreg(0, pmuserenr_el0); > } > > -static inline void ___activate_traps(struct kvm_vcpu *vcpu) > +static inline void ___activate_traps(struct kvm_vcpu *vcpu, u64 hcr) > { > - u64 hcr = vcpu->arch.hcr_el2; > - > if (cpus_have_final_cap(ARM64_WORKAROUND_CAVIUM_TX2_219_TVM)) > hcr |= HCR_TVM; > > diff --git a/arch/arm64/kvm/hyp/nvhe/switch.c > b/arch/arm64/kvm/hyp/nvhe/switch.c > index 6410d21d8695..61a5627fd456 100644 > --- a/arch/arm64/kvm/hyp/nvhe/switch.c > +++ b/arch/arm64/kvm/hyp/nvhe/switch.c > @@ -38,7 +38,7 @@ static void __activate_traps(struct kvm_vcpu *vcpu) > { > u64 val; > > - ___activate_traps(vcpu); > + ___activate_traps(vcpu, vcpu->arch.hcr_el2); > __activate_traps_common(vcpu); > > val = vcpu->arch.cptr_el2; > diff --git a/arch/arm64/kvm/hyp/vhe/switch.c b/arch/arm64/kvm/hyp/vhe/switch.c > index 82ddaebe66de..6ed9e4893a02 100644 > --- a/arch/arm64/kvm/hyp/vhe/switch.c > +++ b/arch/arm64/kvm/hyp/vhe/switch.c > @@ -32,9 +32,14 @@ DEFINE_PER_CPU(unsigned long, kvm_hyp_vector); > > static void __activate_traps(struct kvm_vcpu *vcpu) > { > + u64 hcr = vcpu->arch.hcr_el2; > u64 val; > > - ___activate_traps(vcpu); > + /* Trap VM sysreg accesses if an EL2 guest is not using VHE. */ > + if (vcpu_is_el2(vcpu) && !vcpu_el2_e2h_is_set(vcpu)) > + hcr |= HCR_TVM | HCR_TRVM; > + > + ___activate_traps(vcpu, hcr); > > val = read_sysreg(cpacr_el1); > val |= CPACR_EL1_TTA; > diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c > index 102bc4906723..9d3520f1d17a 100644 > --- a/arch/arm64/kvm/sys_regs.c > +++ b/arch/arm64/kvm/sys_regs.c > @@ -322,8 +322,15 @@ static void get_access_mask(const struct sys_reg_desc > *r, u64 *mask, u64 *shift) > > /* > * Generic accessor for VM registers. Only called as long as HCR_TVM > - * is set. If the guest enables the MMU, we stop trapping the VM > - * sys_regs and leave it in complete control of the caches. > + * is set. > + * > + * This is set in two cases: either (1) we're running at vEL2, or (2) > + * we're running at EL1 and the guest has its MMU off. > + * > + * (1) TVM/TRVM is set, as we need to virtualise some of the VM > + * registers for the guest hypervisor > + * (2) Once the guest enables the MMU, we stop trapping the VM sys_regs > + * and leave it in complete control of the caches. > */ > static bool access_vm_reg(struct kvm_vcpu *vcpu, > struct sys_reg_params *p, > @@ -332,7 +339,13 @@ static bool access_vm_reg(struct kvm_vcpu *vcpu, > bool was_enabled = vcpu_has_cache_enabled(vcpu); > u64 val, mask, shift; > > - BUG_ON(!p->is_write); > + /* We don't expect TRVM on the host */
I don't get what that means. Isn't KVM setting HCR_EL2.TRVM to trap reads? Other than that, the patch looks good: Reviewed-by: Alexandru Elisei <[email protected]> Thanks, Alex > + BUG_ON(!vcpu_is_el2(vcpu) && !p->is_write); > + > + if (!p->is_write) { > + p->regval = vcpu_read_sys_reg(vcpu, r->reg); > + return true; > + } > > get_access_mask(r, &mask, &shift); > > -- > 2.30.2 > _______________________________________________ kvmarm mailing list [email protected] https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
