It is similar with the PAN，when the guest traps to el2，it will reset the
pstate.PAN<http://pstate.PAN> to 0, and continue run。In fact the host
pstate.UAO<http://pstate.UAO> can be 1, but guest change it to 0 when trap to
EL2。so after swich to host，need to check whether set
pstate.UAO<http://pstate.UAO> again。
发件人：Vladimir Murzin
收件人：耿东久,marc.zyngier,christoffer.d...@linaro.org,pbonz...@redhat.com,rkrc...@redhat.com,linux-arm-ker...@lists.infradead.org,kvmarm@lists.cs.columbia.edu,k...@vger.kernel.org,linux-kernel,suzuki.poul...@arm.com,mark.rutl...@arm.com,Catalin
Marinas
抄送：James Morse,张海斌,黄韶宇
时间：2017-09-06 22:41:09
主题:Re: [PATCH] arm64: KVM: VHE: save and restore some PSTATE bits
On 06/09/17 15:10, gengdongjiu wrote:
> Hi, Vladimir
>
>>>> Do you see effect of "PAN is unexpectedly enabled"?
>>> In fact I did not encounter this case, but I think it can exist.
>>> I think if host OS dynamically disable PAN, it wants the host kernel access
>>> the user space address space not through copy_to/from_user
>> API.
>>> Now if it is unexpectedly enabled, when host kernel still accesses the user
>>> space address, it will happen MMU fault exception.
>>
>> And this is expected! The only allowed channel for kernel <-> user is
>> uaccess API.
>>
>> I guess that you have test (and that great!) which violates that rule (for
>> testing purpose, why not?) and now you are trying to fit kernel into
>> it...
>
>
> If you think that makes sense for it, we do not consider the paste.PAN in the
> world-switch.
> For the pstate.UAO issue, do you agree my fixing or you have other
> suggestion? Also to other reviewer. Thanks.
It would help if you give precise description on "pstate.UAO issue".
Thanks
Vladimir
>
> diff --git a/arch/arm64/kvm/hyp/sysreg-sr.c b/arch/arm64/kvm/hyp/sysreg-sr.c
> index 9341376..c3dd761 100644
> --- a/arch/arm64/kvm/hyp/sysreg-sr.c
> +++ b/arch/arm64/kvm/hyp/sysreg-sr.c
> @@ -21,6 +21,8 @@
> #include <asm/kvm_asm.h>
> #include <asm/kvm_hyp.h>
>
> +#include <asm/exec.h>
>
> /* Yes, this does nothing, on purpose */
> static void __hyp_text __sysreg_do_nothing(struct kvm_cpu_context *ctxt) { }
>
> @@ -121,8 +123,13 @@ static void __hyp_text __sysreg_restore_state(struct
> kvm_cpu_context *ctxt)
> write_sysreg_el1(ctxt->gp_regs.spsr[KVM_SPSR_EL1],spsr);
> }
>
> +static void __hyp_text __sysreg_restore_state_vhe(struct kvm_cpu_context
> *ctxt)
> +{
> + uao_thread_switch(current);
> +}
> +
> static hyp_alternate_select(__sysreg_call_restore_host_state,
> - __sysreg_restore_state, __sysreg_do_nothing,
> + __sysreg_restore_state,
> __sysreg_restore_state_vhe,
> ARM64_HAS_VIRT_HOST_EXTN);
>
> void __hyp_text __sysreg_restore_host_state(struct kvm_cpu_context *ctxt)
>
>
>>
>> Cheers
>> Vladimir
>>
>>>
>>>
>>>>
>>>> Cheers
>>>> Vladimir
>>>>
>>>>>
>>>>>>
>>>>>> Cheers
>>>>>> Vladimir
>>>>>>
>>>>>> .
>>>>>>
>>>>>
>>>>>
>>>>
>>>>
>>>> .
>>>>
>>>
>>>
>
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