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

Marc Zyngier
2019-07-03T13:09:43Z

On 24/06/2019 16:07, Julien Thierry wrote:
>
>
> 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.

Yeah, I wanted to actually squash most of this patch into #13, and got
sidetracked. Definitely room for improvement. I may even bring in the
rework I mentioned against #13.

Thanks,

M.
--
Jazz is not dead. It just smells funny...