Hi Marc, On Fri, Jan 28, 2022 at 12:18:20PM +0000, Marc Zyngier wrote: > Some EL2 system registers immediately affect the current execution > of the system, so we need to use their respective EL1 counterparts. > For this we need to define a mapping between the two. In general, > this only affects non-VHE guest hypervisors, as VHE system registers > are compatible with the EL1 counterparts. > > These helpers will get used in subsequent patches. > > Co-developed-by: Andre Przywara <andre.przyw...@arm.com> > Signed-off-by: Andre Przywara <andre.przyw...@arm.com> > Signed-off-by: Marc Zyngier <m...@kernel.org> > --- > arch/arm64/include/asm/kvm_nested.h | 54 +++++++++++++++++++++++++++++ > 1 file changed, 54 insertions(+) > > diff --git a/arch/arm64/include/asm/kvm_nested.h > b/arch/arm64/include/asm/kvm_nested.h > index fd601ea68d13..5a85be6d8eb3 100644 > --- a/arch/arm64/include/asm/kvm_nested.h > +++ b/arch/arm64/include/asm/kvm_nested.h > @@ -2,6 +2,7 @@ > #ifndef __ARM64_KVM_NESTED_H > #define __ARM64_KVM_NESTED_H > > +#include <linux/bitfield.h> > #include <linux/kvm_host.h> > > static inline bool vcpu_has_nv(const struct kvm_vcpu *vcpu) > @@ -11,4 +12,57 @@ static inline bool vcpu_has_nv(const struct kvm_vcpu *vcpu) > test_bit(KVM_ARM_VCPU_HAS_EL2, vcpu->arch.features)); > } > > +/* Translation helpers from non-VHE EL2 to EL1 */ > +static inline u64 tcr_el2_ps_to_tcr_el1_ips(u64 tcr_el2) > +{ > + return (u64)FIELD_GET(TCR_EL2_PS_MASK, tcr_el2) << TCR_IPS_SHIFT; > +} > + > +static inline u64 translate_tcr_el2_to_tcr_el1(u64 tcr) > +{ > + return TCR_EPD1_MASK | /* disable TTBR1_EL1 */ > + ((tcr & TCR_EL2_TBI) ? TCR_TBI0 : 0) | > + tcr_el2_ps_to_tcr_el1_ips(tcr) | > + (tcr & TCR_EL2_TG0_MASK) | > + (tcr & TCR_EL2_ORGN0_MASK) | > + (tcr & TCR_EL2_IRGN0_MASK) | > + (tcr & TCR_EL2_T0SZ_MASK); > +} > + > +static inline u64 translate_cptr_el2_to_cpacr_el1(u64 cptr_el2) > +{ > + u64 cpacr_el1 = 0; > + > + if (cptr_el2 & CPTR_EL2_TTA) > + cpacr_el1 |= CPACR_EL1_TTA; > + if (!(cptr_el2 & CPTR_EL2_TFP)) > + cpacr_el1 |= CPACR_EL1_FPEN; > + if (!(cptr_el2 & CPTR_EL2_TZ)) > + cpacr_el1 |= CPACR_EL1_ZEN; > + > + return cpacr_el1; > +} > + > +static inline u64 translate_sctlr_el2_to_sctlr_el1(u64 val) > +{ > + /* Only preserve the minimal set of bits we support */ > + val &= (SCTLR_ELx_M | SCTLR_ELx_A | SCTLR_ELx_C | SCTLR_ELx_SA | > + SCTLR_ELx_I | SCTLR_ELx_IESB | SCTLR_ELx_WXN | SCTLR_ELx_EE);
Checked that the bit positions are the same between SCTLR_EL2 and SCTLR_EL1. I think the IESB bit (bit 21) should be after the WXN bit (bit 19) to be consistent; doesn't really matter either way. > + val |= SCTLR_EL1_RES1; > + > + return val; > +} > + > +static inline u64 translate_ttbr0_el2_to_ttbr0_el1(u64 ttbr0) > +{ > + /* Clear the ASID field */ > + return ttbr0 & ~GENMASK_ULL(63, 48); > +} > + > +static inline u64 translate_cnthctl_el2_to_cntkctl_el1(u64 cnthctl) > +{ > + return ((FIELD_GET(CNTHCTL_EL1PCTEN | CNTHCTL_EL1PCEN, cnthctl) << 10) | > + (cnthctl & (CNTHCTL_EVNTI | CNTHCTL_EVNTDIR | CNTHCTL_EVNTEN))); I asked about the field positions in the previous series and this is what you replied: > It's a classic one. Remember that we are running VHE, and remapping a > nVHE view of CNTHCTL_EL2 into the VHE view *for the guest*, and that > these things are completely shifted around (it has the CNTKCTL_EL1 > format). > > For example, on nVHE, CNTHCTL_EL2.EL1PCTEN is bit 0. On nVHE, this is > bit 10. That's why we have this shift, and that you now need some > paracetamol. > > You can also look at the way we deal with the same stuff in > kvm_timer_init_vhe()". Here's how this function is used in vhe/sysreg-sr.c: static void __sysreg_restore_vel2_state(struct kvm_cpu_context *ctxt) { [..] if (__vcpu_el2_e2h_is_set(ctxt)) { [..] } else { [..] val = translate_cnthctl_el2_to_cntkctl_el1(ctxt_sys_reg(ctxt, CNTHCTL_EL2)); write_sysreg_el1(val, SYS_CNTKCTL); } [..] } CNTHCTL_EL2 is a pure EL2 register. The translate function is called when guest HCR_EL2.E2H is not set, therefore virtual CNTHCTL_EL2 has the non-VHE format. And the result of the function is used to write to the hardware CNTKCTL_EL1 register (using the CNTKCTL_EL12 encoding), which is different from the CNTHCTL_EL2 register. CNTKCTL_EL1 also always has the same format regardless of the value of the HCR_EL2.E2H bit. I don't understand what the host running with VHE has to do with the translate function. Thanks, Alex > +} > + > #endif /* __ARM64_KVM_NESTED_H */ > -- > 2.30.2 > _______________________________________________ kvmarm mailing list kvmarm@lists.cs.columbia.edu https://lists.cs.columbia.edu/mailman/listinfo/kvmarm