| Message ID | 20170601102117.17750-4-marc.zyngier@arm.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Thu, Jun 01, 2017 at 11:20:55AM +0100, Marc Zyngier wrote: > As we're about to trap CP15 accesses and handle them at EL2, we > need to evaluate whether or not the condition flags are valid, > as an implementation is allowed to trap despite the condition > not being met. > > Tagging the function as __hyp_text allows this. is the cc_map also guaranteed to work (by simple reference) in EL2 then? Thanks, -Christoffer > > Reviewed-by: Eric Auger <eric.auger@redhat.com> > Signed-off-by: Marc Zyngier <marc.zyngier@arm.com> > --- > virt/kvm/arm/aarch32.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/virt/kvm/arm/aarch32.c b/virt/kvm/arm/aarch32.c > index 528af4b2d09e..79c7c357804b 100644 > --- a/virt/kvm/arm/aarch32.c > +++ b/virt/kvm/arm/aarch32.c > @@ -60,7 +60,7 @@ static const unsigned short cc_map[16] = { > /* > * Check if a trapped instruction should have been executed or not. > */ > -bool kvm_condition_valid32(const struct kvm_vcpu *vcpu) > +bool __hyp_text kvm_condition_valid32(const struct kvm_vcpu *vcpu) > { > unsigned long cpsr; > u32 cpsr_cond; > -- > 2.11.0 >
On 04/06/17 13:11, Christoffer Dall wrote: > On Thu, Jun 01, 2017 at 11:20:55AM +0100, Marc Zyngier wrote: >> As we're about to trap CP15 accesses and handle them at EL2, we >> need to evaluate whether or not the condition flags are valid, >> as an implementation is allowed to trap despite the condition >> not being met. >> >> Tagging the function as __hyp_text allows this. > > is the cc_map also guaranteed to work (by simple reference) in EL2 then? Yes. By virtue of being const, this ends up in the read-only part of the kernel, which we always map at EL2. Thanks, M.
On Mon, Jun 05, 2017 at 09:13:53AM +0100, Marc Zyngier wrote: > On 04/06/17 13:11, Christoffer Dall wrote: > > On Thu, Jun 01, 2017 at 11:20:55AM +0100, Marc Zyngier wrote: > >> As we're about to trap CP15 accesses and handle them at EL2, we > >> need to evaluate whether or not the condition flags are valid, > >> as an implementation is allowed to trap despite the condition > >> not being met. > >> > >> Tagging the function as __hyp_text allows this. > > > > is the cc_map also guaranteed to work (by simple reference) in EL2 then? > > Yes. By virtue of being const, this ends up in the read-only part of the > kernel, which we always map at EL2. > And why don't we have to do any address-translation-to-hyp tricks on the address? Are we guaranteed that it's a relative address and everything is relocated with the same offset, or how was that again? Thanks, -Christoffer
On 05/06/17 09:23, Christoffer Dall wrote: > On Mon, Jun 05, 2017 at 09:13:53AM +0100, Marc Zyngier wrote: >> On 04/06/17 13:11, Christoffer Dall wrote: >>> On Thu, Jun 01, 2017 at 11:20:55AM +0100, Marc Zyngier wrote: >>>> As we're about to trap CP15 accesses and handle them at EL2, we >>>> need to evaluate whether or not the condition flags are valid, >>>> as an implementation is allowed to trap despite the condition >>>> not being met. >>>> >>>> Tagging the function as __hyp_text allows this. >>> >>> is the cc_map also guaranteed to work (by simple reference) in EL2 then? >> >> Yes. By virtue of being const, this ends up in the read-only part of the >> kernel, which we always map at EL2. >> > > And why don't we have to do any address-translation-to-hyp tricks on the > address? Are we guaranteed that it's a relative address and everything > is relocated with the same offset, or how was that again? Arghh, I completely missed this. Yeah, it works because this is a single compilation unit, that the array is static, used only once, and that the compiler is using relative addressing and not playing any dirty tricks on us. We could make the whole thing private to kvm_condition_valid32, but that's not more of a guarantee that things won't break if the compiler decides to generate absolute addresses. Thanks, M.
diff --git a/virt/kvm/arm/aarch32.c b/virt/kvm/arm/aarch32.c index 528af4b2d09e..79c7c357804b 100644 --- a/virt/kvm/arm/aarch32.c +++ b/virt/kvm/arm/aarch32.c @@ -60,7 +60,7 @@ static const unsigned short cc_map[16] = { /* * Check if a trapped instruction should have been executed or not. */ -bool kvm_condition_valid32(const struct kvm_vcpu *vcpu) +bool __hyp_text kvm_condition_valid32(const struct kvm_vcpu *vcpu) { unsigned long cpsr; u32 cpsr_cond;