Re: [PATCH 15/59] KVM: arm64: nv: Refactor vcpu_{read,write}_sys_reg

Julien Thierry
2019-06-24T15:07:59Z

On 06/21/2019 10:37 AM, Marc Zyngier wrote:
> Extract the direct HW accessors for later reuse.
>
> Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
> ---
> arch/arm64/kvm/sys_regs.c | 247 +++++++++++++++++++++-----------------
> 1 file changed, 139 insertions(+), 108 deletions(-)
>
> diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
> index 2b8734f75a09..e181359adadf 100644
> --- a/arch/arm64/kvm/sys_regs.c
> +++ b/arch/arm64/kvm/sys_regs.c
> @@ -182,99 +182,161 @@ const struct el2_sysreg_map *find_el2_sysreg(const struct el2_sysreg_map *map,
> return entry;
> }
>
> +static bool __vcpu_read_sys_reg_from_cpu(int reg, u64 *val)
> +{
> + /*
> + * System registers listed in the switch are not saved on every
> + * exit from the guest but are only saved on vcpu_put.
> + *
> + * Note that MPIDR_EL1 for the guest is set by KVM via VMPIDR_EL2 but
> + * should never be listed below, because the guest cannot modify its
> + * own MPIDR_EL1 and MPIDR_EL1 is accessed for VCPU A from VCPU B's
> + * thread when emulating cross-VCPU communication.
> + */
> + switch (reg) {
> + case CSSELR_EL1: *val = read_sysreg_s(SYS_CSSELR_EL1); break;
> + case SCTLR_EL1: *val = read_sysreg_s(SYS_SCTLR_EL12); break;
> + case ACTLR_EL1: *val = read_sysreg_s(SYS_ACTLR_EL1); break;
> + case CPACR_EL1: *val = read_sysreg_s(SYS_CPACR_EL12); break;
> + case TTBR0_EL1: *val = read_sysreg_s(SYS_TTBR0_EL12); break;
> + case TTBR1_EL1: *val = read_sysreg_s(SYS_TTBR1_EL12); break;
> + case TCR_EL1: *val = read_sysreg_s(SYS_TCR_EL12); break;
> + case ESR_EL1: *val = read_sysreg_s(SYS_ESR_EL12); break;
> + case AFSR0_EL1: *val = read_sysreg_s(SYS_AFSR0_EL12); break;
> + case AFSR1_EL1: *val = read_sysreg_s(SYS_AFSR1_EL12); break;
> + case FAR_EL1: *val = read_sysreg_s(SYS_FAR_EL12); break;
> + case MAIR_EL1: *val = read_sysreg_s(SYS_MAIR_EL12); break;
> + case VBAR_EL1: *val = read_sysreg_s(SYS_VBAR_EL12); break;
> + case CONTEXTIDR_EL1: *val = read_sysreg_s(SYS_CONTEXTIDR_EL12);break;
> + case TPIDR_EL0: *val = read_sysreg_s(SYS_TPIDR_EL0); break;
> + case TPIDRRO_EL0: *val = read_sysreg_s(SYS_TPIDRRO_EL0); break;
> + case TPIDR_EL1: *val = read_sysreg_s(SYS_TPIDR_EL1); break;
> + case AMAIR_EL1: *val = read_sysreg_s(SYS_AMAIR_EL12); break;
> + case CNTKCTL_EL1: *val = read_sysreg_s(SYS_CNTKCTL_EL12); break;
> + case PAR_EL1: *val = read_sysreg_s(SYS_PAR_EL1); break;
> + case DACR32_EL2: *val = read_sysreg_s(SYS_DACR32_EL2); break;
> + case IFSR32_EL2: *val = read_sysreg_s(SYS_IFSR32_EL2); break;
> + case DBGVCR32_EL2: *val = read_sysreg_s(SYS_DBGVCR32_EL2); break;
> + default: return false;
> + }
> +
> + return true;
> +}
> +
> +static bool __vcpu_write_sys_reg_to_cpu(u64 val, int reg)
> +{
> + /*
> + * System registers listed in the switch are not restored on every
> + * entry to the guest but are only restored on vcpu_load.
> + *
> + * Note that MPIDR_EL1 for the guest is set by KVM via VMPIDR_EL2 but
> + * should never be listed below, because the the MPIDR should only be
> + * set once, before running the VCPU, and never changed later.
> + */
> + switch (reg) {
> + case CSSELR_EL1: write_sysreg_s(val, SYS_CSSELR_EL1); break;
> + case SCTLR_EL1: write_sysreg_s(val, SYS_SCTLR_EL12); break;
> + case ACTLR_EL1: write_sysreg_s(val, SYS_ACTLR_EL1); break;
> + case CPACR_EL1: write_sysreg_s(val, SYS_CPACR_EL12); break;
> + case TTBR0_EL1: write_sysreg_s(val, SYS_TTBR0_EL12); break;
> + case TTBR1_EL1: write_sysreg_s(val, SYS_TTBR1_EL12); break;
> + case TCR_EL1: write_sysreg_s(val, SYS_TCR_EL12); break;
> + case ESR_EL1: write_sysreg_s(val, SYS_ESR_EL12); break;
> + case AFSR0_EL1: write_sysreg_s(val, SYS_AFSR0_EL12); break;
> + case AFSR1_EL1: write_sysreg_s(val, SYS_AFSR1_EL12); break;
> + case FAR_EL1: write_sysreg_s(val, SYS_FAR_EL12); break;
> + case MAIR_EL1: write_sysreg_s(val, SYS_MAIR_EL12); break;
> + case VBAR_EL1: write_sysreg_s(val, SYS_VBAR_EL12); break;
> + case CONTEXTIDR_EL1: write_sysreg_s(val, SYS_CONTEXTIDR_EL12);break;
> + case TPIDR_EL0: write_sysreg_s(val, SYS_TPIDR_EL0); break;
> + case TPIDRRO_EL0: write_sysreg_s(val, SYS_TPIDRRO_EL0); break;
> + case TPIDR_EL1: write_sysreg_s(val, SYS_TPIDR_EL1); break;
> + case AMAIR_EL1: write_sysreg_s(val, SYS_AMAIR_EL12); break;
> + case CNTKCTL_EL1: write_sysreg_s(val, SYS_CNTKCTL_EL12); break;
> + case PAR_EL1: write_sysreg_s(val, SYS_PAR_EL1); break;
> + case DACR32_EL2: write_sysreg_s(val, SYS_DACR32_EL2); break;
> + case IFSR32_EL2: write_sysreg_s(val, SYS_IFSR32_EL2); break;
> + case DBGVCR32_EL2: write_sysreg_s(val, SYS_DBGVCR32_EL2); break;
> + default: return false;
> + }
> +
> + return true;
> +}
> +
> u64 vcpu_read_sys_reg(const struct kvm_vcpu *vcpu, int reg)
> {
> - u64 val;
> + u64 val = 0x8badf00d8badf00d;
>
> if (!vcpu->arch.sysregs_loaded_on_cpu)
> - goto immediate_read;
> + goto memory_read;
>
> if (unlikely(sysreg_is_el2(reg))) {
> const struct el2_sysreg_map *el2_reg;
>
> if (!is_hyp_ctxt(vcpu))
> - goto immediate_read;
> + goto memory_read;
>
> switch (reg) {
> + case ELR_EL2:
> + return read_sysreg_el1(SYS_ELR);

Hmmm, This change feels a bit out of place.

Also, patch 13 added ELR_EL2 and SP_EL2 to the switch cases for physical
sysreg accesses. Now ELR_EL2 is moved out of the main switch cases and
SP_EL2 is completely omitted.

I'd say either patch 13 needs to be reworked or there is a separate
patch that should be extracted from this patch to have an intermediate
state, or the commit message on this patch should be more detailed.

Cheers,

--
Julien Thierry