On Wed, Jan 25, 2017 at 8:22 AM, Christoffer Dall <christoffer.dall@xxxxxxxxxx> wrote:
On Tue, Jan 24, 2017 at 09:50:04PM +0000, Raz wrote:
> Hello
>
> I am trying to boot EL1 kernel in a platform based on Armv8.1.
> I am using fvp as a hardware.
> What I am trying to achieve is to execute some kernel code in
> EL2 exception level..
When you boot a reasonably recent kernel on VHE, it will execute in EL2,
so all the code you're executing will be at EL2, so I think you've
already achieved what you're trying to do.
>
> The current VHE patch is booting the kernel into EL2. So I took an older
> kernel
> and I tried to set TTBR1_EL2 to access kernel memory as if it is TTBR1_EL1
> .
That won't work unless you set the E2H bit, see the ARMv8.1
documentation.
If you boot a kernel that doesn't have the necessary bits to enable VHE,
then you'll just run as on a non-VHE system with the main kernel running
at EL1 and a stub installed at EL2 which eventually gets replaced by the
KVM hyp lowvisor code in EL2.
>
> It is theoretically possible ?
I'm not sure what you're asking?
> Setting TTBR1_EL2 to TTBR1_EL1
> and enabling mmu thtough sctlr_el2 does not work.
>
Again, not sure what you're trying to do. If you're running in EL1
(because you're old kernel drops you to EL1) then trying to access EL2
registers obviously won't work.
I created my own vector instead of kvm's . I am doing that because I want to create a sort of secured execution context by using a hypervisor. It is an academic work.
I managed to do that by the way. I am calling regular kernel code in EL2. so thank you.
If you run a VHE kernel, it will have already set the _EL2 registers to
the values you want (but it will use _EL1 register access intructions to
do so, and they are transparently rewritten by hardware to program the
corresponding _EL2 registers).
Hope this helps,
-Christoffer
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