Although we've implemented PSCI 0.1, 0.2 and 1.0, we expose either 0.1
or 1.0 to a guest, defaulting to the latest version of the PSCI
implementation that is compatible with the requested version. This is
no different from doing a firmware upgrade on KVM.
But in order to give a chance to hypothetical badly implemented guests
that would have a fit by discovering something other than PSCI 0.2,
let's provide a new API that allows userspace to pick one particular
version of the API.
This is implemented as a new class of "firmware" registers, where
we expose the PSCI version. This allows the PSCI version to be
save/restored as part of a guest migration, and also set to
any supported version if the guest requires it.
Cc: stable@vger.kernel.org #4.16
Reviewed-by: Christoffer Dall <cdall@kernel.org>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
The reason I added this documentation originally was that the concept of
"never taking the interrupt", but just use the timer to generate an exit
from the guest, was confusing to most, and we had to explain it several
times over. But as we can clearly see, we've failed to update the
documentation as the code has evolved, and people who need to understand
these details are probably better off reading the code.
Let's lighten our maintenance burden slightly and just get rid of this.
Acked-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
In order to help people understanding the hyp-stub API that exists
between the host kernel and the hypervisor mode (whether a hypervisor
has been installed or not), let's document said API.
As with any form of documentation, I expect it to become obsolete
and completely misleading within 20 minutes after having being merged.
Acked-by: Russell King <rmk+kernel@armlinux.org.uk>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Christoffer Dall <cdall@linaro.org>
Forwarded physical interrupts on arm/arm64 is a tricky concept and the
way we deal with them is not apparently easy to understand by reading
various specs.
Therefore, add a proper documentation file explaining the flow and
rationale of the behavior of the vgic.
Some of this text was contributed by Marc Zyngier and edited by me.
Omissions and errors are all mine.
Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
