On 06/09/17 16:08, gengdongjiu wrote: > 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。 What negative effect do you see with change UAO to 0 (i.e. do not override)? P. S. Please, avoid HTML and top posting Vladimir > *发件人：*Vladimir Murzin > *收件人：*耿东久,marc.zyngier,christoffer.dall@xxxxxxxxxx,pbonzini@xxxxxxxxxx,rkrcmar@xxxxxxxxxx,linux-arm-kernel@xxxxxxxxxxxxxxxxxxx,kvmarm@xxxxxxxxxxxxxxxxxxxxx,kvm@xxxxxxxxxxxxxxx,linux-kernel,suzuki.poulose@xxxxxxx,mark.rutland@xxxxxxx,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 >>>>>>> >>>>>>> . >>>>>>> >>>>>> >>>>>> >>>>> >>>>> >>>>> . >>>>> >>>> >>>> >> >
