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

[Peter Crosthwaite]

On Fri, Oct 30, 2015 at 3:04 PM, Peter Maydell <address@hidden> wrote:
> 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?)
>

I think so. This patch series repaired both Higbank and Midway,
although I am use a very generic Kernel so maybe a Kernel config gets
Midway in better shape. My gut feeling is yes, we need SMC for the a15
too.

Regards,
Peter

> thanks
> -- PMM