Re: [Qemu-devel] [PATCH v2 4/5] arm: boot: Add secure_board_setup flag

[Peter Maydell]

On 30 October 2015 at 21:24, Peter Crosthwaite
<address@hidden> wrote:
> On Fri, Oct 30, 2015 at 2:14 PM, Peter Maydell <address@hidden> wrote:
>> The other question is what happens on a board like this if
>> the user says -enable-kvm -cpu cortex-a15 ? Does that get us
>> a CPU without the EL3 property? (I forget...) In any case it
>> shouldn't be an error unless the board genuinely can't work
>> with KVM at all, and if we're using KVM then the board
>> blob definitely won't be running in Secure (and can't flip
>> to Monitor mode either).
>
> I think all we can do is exit on !kvm and have the board if() the
> firmware blob for the same. What is supposed to actually happen when a
> virtualized guest running under KVM calls SMC? Does the VM have any
> say on what that SMC does or is that the property of the host OS? The
> latter suggests that Highbank Linux simply cannot be run under KVM.

The VM can intercept SMC, yes (HCR.TSC causes SMC to trap to Hyp,
regardless of what the SCR settings are). I don't know whether KVM
actually does trap it. Typically the need for SMC calls seems to
have only been for A9 and earlier CPUs, though -- mostly the A15
managed to avoid the requirement, so it hasn't been necessary for
KVM to deal with random board specific SMC handling. (Do we need
the SMC handling for the A15 variant of the highbank model?)

thanks
-- PMM