linux-kernel - Re: [PATCH] KVM: arm64: add esr_el2 and far

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Message-ID: <085aaa48-3d8d-5af4-0329-6db8175f7032@huawei.com>
Date:   Tue, 8 Aug 2017 02:59:44 +0800
From:   gengdongjiu <gengdongjiu@...wei.com>
To:     Marc Zyngier <marc.zyngier@....com>, <christoffer.dall@...aro.org>,
        <pbonzini@...hat.com>, <rkrcmar@...hat.com>,
        <catalin.marinas@....com>, <will.deacon@....com>,
        <linux-arm-kernel@...ts.infradead.org>,
        <kvmarm@...ts.cs.columbia.edu>, <kvm@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, James Morse <James.Morse@....com>
Subject: Re: [PATCH] KVM: arm64: add esr_el2 and far_el2 to sysreg

Marc,

On 2017/8/8 0:56, Marc Zyngier wrote:
> On 07/08/17 17:23, gengdongjiu wrote:
>> 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.
> 
> Usespace may need some fault information, but certainly not the full set
> of FAR_EL2/ESR_EL2. What it needs is a very small set of well defined
> information, properly abstracted, and not data that is completely
> private to the hypervisor.

Marc, just now I update the patch, may be use the vcpu->arch.fault.esr_el2 and vcpu->arch.fault.far_el2 to set the vcpu_sys_reg(vcpu,FAR_EL2)/vcpu_sys_reg(vcpu,ESR_EL2) can be better.
Now the user space can not directly get the vcpu->arch.faul.xxxx value, so need use vcpu_sys_reg to pass.



> 
> Thanks,
> 
> 	M.
>>
>>
>>
>>
>> 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@...wei.com>
>>>> Signed-off-by: Quanming Wu <wuquanming@...wei.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.
>>>
>>
> 
>