arm/arm64: Probe for the presence of KVM hypervisor

Although the SMCCC specification provides some limited functionality for
describing the presence of hypervisor and firmware services, this is
generally applicable only to functions designated as "Arm Architecture
Service Functions" and no portable discovery mechanism is provided for
standard hypervisor services, despite having a designated range of
function identifiers reserved by the specification.

In an attempt to avoid the need for additional firmware changes every
time a new function is added, introduce a UID to identify the service
provider as being compatible with KVM. Once this has been established,
additional services can be discovered via a feature bitmap.

Reviewed-by: Steven Price <steven.price@arm.com>
Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Jianyong Wu <jianyong.wu@arm.com>
[maz: move code to its own file, plug it into PSCI]
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20201209060932.212364-2-jianyong.wu@arm.com

firmware: smccc: Add ARCH_SOC_ID support

SMCCC v1.2 adds a new optional function SMCCC_ARCH_SOC_ID to obtain a
SiP defined SoC identification value. Add support for the same.

Also using the SoC bus infrastructure, let us expose the platform
specific SoC atrributes under sysfs.

There are various ways in which it can be represented in shortened form
for efficiency and ease of parsing for userspace. The chosen form is
described in the ABI document.

Link: https://lore.kernel.org/r/20200625095939.50861-1-sudeep.holla@arm.com
Cc: Etienne Carriere <etienne.carriere@st.com>
Reviewed-by: Steven Price <steven.price@arm.com>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>

firmware: smccc: Refactor SMCCC specific bits into separate file

In order to add newer SMCCC v1.1+ functionality and to avoid cluttering
PSCI firmware driver with SMCCC bits, let us move the SMCCC specific
details under drivers/firmware/smccc/smccc.c

We can also drop conduit and smccc_version from psci_operations structure
as SMCCC was the sole user and now it maintains those.

No functionality change in this patch though.

Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
Tested-by: Etienne Carriere <etienne.carriere@st.com>
Reviewed-by: Etienne Carriere <etienne.carriere@st.com>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Link: https://lore.kernel.org/r/20200518091222.27467-6-sudeep.holla@arm.com
Signed-off-by: Will Deacon <will@kernel.org>