Re: [PATCH] KVM: arm64: Do not let a L1 hypervisor access the *32_EL2 sysregs

[Marc Zyngier]

On 16 October 2023 15:15:02 BST, Miguel Luis <miguel.luis at oracle.com> wrote:
>Hi Marc,
>
>> On 13 Oct 2023, at 22:33, Marc Zyngier <maz at kernel.org> wrote:
>> 
>> DBGVCR32_EL2, DACR32_EL2, IFSR32_EL2 and FPEXC32_EL2 are required to
>> UNDEF when AArch32 isn't implemented, which is definitely the case when
>> running NV.
>> 
>> Given that this is the only case where these registers can trap,
>> unconditionally inject an UNDEF exception.
>> 
>> Signed-off-by: Marc Zyngier <maz at kernel.org>
>> ---
>> arch/arm64/kvm/sys_regs.c | 8 ++++----
>> 1 file changed, 4 insertions(+), 4 deletions(-)
>> 
>> diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
>> index 0afd6136e275..0071ccccaf00 100644
>> --- a/arch/arm64/kvm/sys_regs.c
>> +++ b/arch/arm64/kvm/sys_regs.c
>> @@ -1961,7 +1961,7 @@ static const struct sys_reg_desc sys_reg_descs[] = {
>> // DBGDTR[TR]X_EL0 share the same encoding
>> { SYS_DESC(SYS_DBGDTRTX_EL0), trap_raz_wi },
>> 
>> - { SYS_DESC(SYS_DBGVCR32_EL2), NULL, reset_val, DBGVCR32_EL2, 0 },
>> + { SYS_DESC(SYS_DBGVCR32_EL2), trap_undef, reset_val, DBGVCR32_EL2, 0 },
>> 
>> { SYS_DESC(SYS_MPIDR_EL1), NULL, reset_mpidr, MPIDR_EL1 },
>> 
>> @@ -2380,18 +2380,18 @@ static const struct sys_reg_desc sys_reg_descs[] = {
>> EL2_REG(VTTBR_EL2, access_rw, reset_val, 0),
>> EL2_REG(VTCR_EL2, access_rw, reset_val, 0),
>> 
>> - { SYS_DESC(SYS_DACR32_EL2), NULL, reset_unknown, DACR32_EL2 },
>> + { SYS_DESC(SYS_DACR32_EL2), trap_undef, reset_unknown, DACR32_EL2 },
>> EL2_REG(HDFGRTR_EL2, access_rw, reset_val, 0),
>> EL2_REG(HDFGWTR_EL2, access_rw, reset_val, 0),
>> EL2_REG(SPSR_EL2, access_rw, reset_val, 0),
>> EL2_REG(ELR_EL2, access_rw, reset_val, 0),
>> { SYS_DESC(SYS_SP_EL1), access_sp_el1},
>> 
>> - { SYS_DESC(SYS_IFSR32_EL2), NULL, reset_unknown, IFSR32_EL2 },
>> + { SYS_DESC(SYS_IFSR32_EL2), trap_undef, reset_unknown, IFSR32_EL2 },
>> EL2_REG(AFSR0_EL2, access_rw, reset_val, 0),
>> EL2_REG(AFSR1_EL2, access_rw, reset_val, 0),
>> EL2_REG(ESR_EL2, access_rw, reset_val, 0),
>> - { SYS_DESC(SYS_FPEXC32_EL2), NULL, reset_val, FPEXC32_EL2, 0x700 },
>> + { SYS_DESC(SYS_FPEXC32_EL2), trap_undef, reset_val, FPEXC32_EL2, 0x700 },
>> 
>
>Should SDER32_EL2 be considered to this same list?
>

This wouldn't make much sense.

This register is only available when running in secure mode, and KVM is firmly non-secure.

Thanks,

        M.

Jazz is not dead, it just smells funny