Re: [PATCH] arm64: KVM: VHE: save and restore some PSTATE bits

[gengdongjiu]

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.

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
> >>>>
> >>>> .
> >>>>
> >>>
> >>>
> >>
> >>
> >> .
> >>
> >
> >