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SubjectRe: [PATCH] KVM: arm64: add esr_el2 and far_el2 to sysreg
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Hi Marc,
As James's suggestion, I move injection SEA Error logic to the user space(Qemu), Qemu sets the related guest OS esr/elr/pstate/spsr
through IOCTL KVM_SET_ONE_REG. For the SEA, when Qemu sets the esr_el1.IL bit, it needs to refer to esr_el2.IL, else Qemu does not know the trapped
instruction was a 16-bit or a 32-bit instruction, also it needs to set far_el1 using far_el2, because this is synchronization abort.




On 2017/8/7 23:57, Marc Zyngier wrote:
> +James, since he deals with all things RAS. Please keep him on CC at all
> times.
>
> On 07/08/17 17:08, Dongjiu Geng wrote:
>> For the firmware-first RAS solution, SEA and SEI is injected
>> by the user space, user space needs to know the esr_el2 and
>> far_el2's value, so add them to sysreg. user space uses
>> the IOCTL KVM_GET_ONE_REG can get their value.
>
> No.
>
> This has zero purpose being exposed to userspace. Userspace sees a VM
> that runs at EL1, and nothing else, so exposing EL2 registers doesn't
> make *any* sense.
>
> If you want something to be exposed to userspace, it has to be properly
> abstracted and describe something that is relevant to the VM. An EL2
> register satisfies none of these conditions.
>
>>
>> Signed-off-by: Dongjiu Geng <gengdongjiu@huawei.com>
>> Signed-off-by: Quanming Wu <wuquanming@huawei.com>
>> ---
>> arch/arm64/include/asm/kvm_host.h | 6 ++++--
>> arch/arm64/kvm/sys_regs.c | 6 ++++++
>> 2 files changed, 10 insertions(+), 2 deletions(-)
>>
>> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
>> index b6242fb..6063eec 100644
>> --- a/arch/arm64/include/asm/kvm_host.h
>> +++ b/arch/arm64/include/asm/kvm_host.h
>> @@ -103,10 +103,12 @@ enum vcpu_sysreg {
>> TTBR0_EL1, /* Translation Table Base Register 0 */
>> TTBR1_EL1, /* Translation Table Base Register 1 */
>> TCR_EL1, /* Translation Control Register */
>> - ESR_EL1, /* Exception Syndrome Register */
>> + ESR_EL1, /* Exception Syndrome Register for EL1 */
>> + ESR_EL2, /* Exception Syndrome Register for EL2 */
>> AFSR0_EL1, /* Auxiliary Fault Status Register 0 */
>> AFSR1_EL1, /* Auxiliary Fault Status Register 1 */
>> - FAR_EL1, /* Fault Address Register */
>> + FAR_EL1, /* Fault Address Register for EL1 */
>> + FAR_EL2, /* Fault Address Register for EL2 */
>> MAIR_EL1, /* Memory Attribute Indirection Register */
>> VBAR_EL1, /* Vector Base Address Register */
>> CONTEXTIDR_EL1, /* Context ID Register */
>> diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
>> index 0e26f8c..0c286bf 100644
>> --- a/arch/arm64/kvm/sys_regs.c
>> +++ b/arch/arm64/kvm/sys_regs.c
>> @@ -987,9 +987,15 @@ static const struct sys_reg_desc sys_reg_descs[] = {
>> /* ESR_EL1 */
>> { Op0(0b11), Op1(0b000), CRn(0b0101), CRm(0b0010), Op2(0b000),
>> access_vm_reg, reset_unknown, ESR_EL1 },
>> + /* ESR_EL2 */
>> + { Op0(0b11), Op1(0b100), CRn(0b0101), CRm(0b0010), Op2(0b000),
>> + access_vm_reg, reset_unknown, ESR_EL2 },
>> /* FAR_EL1 */
>> { Op0(0b11), Op1(0b000), CRn(0b0110), CRm(0b0000), Op2(0b000),
>> access_vm_reg, reset_unknown, FAR_EL1 },
>> + /* FAR_EL2 */
>> + { Op0(0b11), Op1(0b100), CRn(0b0110), CRm(0b0000), Op2(0b000),
>> + access_vm_reg, reset_unknown, FAR_EL2 },
>> /* PAR_EL1 */
>> { Op0(0b11), Op1(0b000), CRn(0b0111), CRm(0b0100), Op2(0b000),
>> NULL, reset_unknown, PAR_EL1 },
>>
>
> Also, what do you return here? All you're doing to return to userspace
> is 0x1de7ec7edbadc0deULL (which perfectly matches this patch).
>
> So for all intents and purposes, this patch is pretty useless.
>
> Thanks,
>
> M.
>

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