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Re: [Xen-devel] [PATCH v4 16/16] xen/arm: add SGI handling for GICv3

On Mon, Jun 16, 2014 at 12:14 AM, Julien Grall <julien.grall@xxxxxxxxxx> wrote:
> Hi Ian,
> On 13 June 2014 09:34, Ian Campbell <Ian.Campbell@xxxxxxxxxx> wrote:
>> On Thu, 2014-06-12 at 22:56 +0100, Julien Grall wrote:
>>> On 12/06/14 07:53, Vijay Kilari wrote:
>>> >     In GICv3 case the sending SGI by guest raises sysreg trap where
>>> > as in GICv2 it raises mmio write trap. So these traps lands in respective
>>> > vgic driver. ( mmio write trap => vgic-v2.c and sysreg => vgic-v3.c)
>>> > These vgic-v{2,3}.c driver calls generic vgic driver to inject SGI to 
>>> > VCPU.
>>> What does prevent a malicious buggy gicv2 guest too call the sysreg
>>> version? AFAIU nothing, so you will end up to interpret GICv2 data as
>>> GICv3 data which will result to a possible security issue.
>> ICC_SRE_EL2.Enable should gate EL1's access to this register. We should
>> certainly set this to the appropriate value corresponding to what we
>> expose to the guest. (I haven't looked if this series does not).
> Thanks for information. I suspect the current GICv3 driver is not
> ready to support
> GICv2 guest. Actually this bit is not context switch.

As per GICv3 spec 4.8.17 it recommends to save and restore ICC_SRE_EL1
register on VM switch. I will added this in next version

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