RE: [RFC PATCH v1] powerpc/prom_init: disable XIVE in Secure VM.

["Cédric Le Goater" <clg@fr.ibm.com>]

On 3/5/20 4:15 PM, Ram Pai wrote:
> On Thu, Mar 05, 2020 at 10:55:45AM +1100, David Gibson wrote:
>> On Wed, Mar 04, 2020 at 04:56:09PM +0100, Cédric Le Goater wrote:
>>> [ ... ]
>>>
>>>> (1) applied the patch which shares the EQ-page with the hypervisor.
>>>> (2) set "kernel_irqchip=off"
>>>> (3) set "ic-mode=xive"
>>>
>>> you don't have to set the interrupt mode. xive should be negotiated
>>> by default.
>>>
>>>> (4) set "svm=on" on the kernel command line.
>>>> (5) no changes to the hypervisor and ultravisor.
>>>>
>>>> And Boom it works!.   So you were right.
>>>
>>> Excellent.
>>>  
>>>> I am sending out the patch for (1) above ASAP.
>>>
>>> Next step, could you please try to do the same with the TIMA and ESB pfn ?
>>> and use KVM.
>>
>> I'm a bit confused by this.  Aren't the TIMA and ESB pages essentially
>> IO pages, rather than memory pages from the guest's point of view?  I
>> assume only memory pages are protected with PEF - I can't even really
>> see what protecting an IO page would even mean.
> 
> It means, that the hypervisor and qemu cannot access the addresses used
> to access the I/O pages. It can only be accessed by Ultravisor and the
> SVM.
> 
> As it stands today, those pages are accessible from the hypervisor
> and not from the SVM or the ultravisor.
> 
> To make it work, we need to enable acccess to those pages from the SVM
> and from the ultravisor.  One thing I am not clear is should we block
> access to those pages from the hypervisor. If yes, than there is no> good way to do that, without hardware help.  If no, than those GPA pages
> can be shared, so that hypervisor/ultravisor/qemu/SVM can all access
> those pages.

They are shared.

KVM will also access them, at interrupt creation, device reset and 
passthrough. QEMU will use them to mask on/off the interrupts in
case of guest migration or machine stop/continue. 

C.