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: NRussell King <rmk+kernel@armlinux.org.uk>
Acked-by: NCatalin Marinas <catalin.marinas@arm.com>
Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>
Signed-off-by: NChristoffer Dall <cdall@linaro.org>

We now return HVC_STUB_ERR when a stub hypercall fails, but we
leave whatever was in r0 on success. Zeroing it on return seems
like a good idea.
Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>
Signed-off-by: NChristoffer Dall <cdall@linaro.org>

We now return HVC_STUB_ERR when a stub hypercall fails, but we
leave whatever was in x0 on success. Zeroing it on return seems
like a good idea.
Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>
Signed-off-by: NChristoffer Dall <cdall@linaro.org>

Nobody is using __hyp_get_vectors anymore, so let's remove both
implementations (hyp-stub and KVM).
Acked-by: NCatalin Marinas <catalin.marinas@arm.com>
Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>
Signed-off-by: NChristoffer Dall <cdall@linaro.org>

Nobody is using __hyp_get_vectors anymore, so let's remove both
implementations (hyp-stub and KVM).
Acked-by: NRussell King <rmk+kernel@armlinux.org.uk>
Acked-by: NCatalin Marinas <catalin.marinas@arm.com>
Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>
Signed-off-by: NChristoffer Dall <cdall@linaro.org>

When the compressed image needs to be relocated to avoid being
overwritten by the decompression process, we need to relocate
the hyp vectors as well so that we can find them once the
decompression has taken effect.

For that, we perform the following calculation:
	u32 v = __hyp_get_vectors();
	v += offset;
	__hyp_set_vectors(v);

But we're guaranteed that the initial value of v as returned by
__hyp_get_vectors is always __hyp_stub_vectors, because we have
just set it by calling __hyp_stub_install.

So let's remove the use of __hyp_get_vectors, and directly use
__hyp_stub_vectors instead.
Acked-by: NRussell King <rmk+kernel@armlinux.org.uk>
Acked-by: NCatalin Marinas <catalin.marinas@arm.com>
Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>
Signed-off-by: NChristoffer Dall <cdall@linaro.org>

Instead of trying to compare the value given by __hyp_get_vectors(),
which doesn't offer any real guarantee to be the stub's address, use
HVC_RESET_VECTORS to make sure we're in a sane state to reinstall
KVM across PM events.
Acked-by: NCatalin Marinas <catalin.marinas@arm.com>
Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>
Signed-off-by: NChristoffer Dall <cdall@linaro.org>

With __cpu_reset_hyp_mode having become fairly dumb, there is no
need for kvm_get_idmap_start anymore.
Acked-by: NCatalin Marinas <catalin.marinas@arm.com>
Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>
Signed-off-by: NChristoffer Dall <cdall@linaro.org>

__cpu_reset_hyp_mode doesn't need to be passed any argument now,
as the hyp-stub implementations are self-contained, and is now
reduced to just calling __hyp_reset_vectors(). Let's drop the
wrapper and use the stub hypercall directly.
Acked-by: NCatalin Marinas <catalin.marinas@arm.com>
Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>
Signed-off-by: NChristoffer Dall <cdall@linaro.org>

Should kvm_reboot() be invoked while guest is running, an IPI
wil be issued, forcing the guest to exit and HYP being reset to
the stubs. We will then try to reenter the guest, only to get
an error (HVC_STUB_ERR).

This patch allows this case to be gracefully handled by exiting
the run loop.
Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>
Signed-off-by: NChristoffer Dall <cdall@linaro.org>

Another missing stub hypercall is HVC_SOFT_RESTART. It turns out
that it is pretty easy to implement in terms of HVC_RESET_VECTORS
(since it needs to turn the MMU off).
Tested-by: NKeerthy <j-keerthy@ti.com>
Acked-by: NRussell King <rmk+kernel@armlinux.org.uk>
Acked-by: NCatalin Marinas <catalin.marinas@arm.com>
Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>
Signed-off-by: NChristoffer Dall <cdall@linaro.org>

We are now able to use the hyp stub to reset HYP mode. Time to
kiss __kvm_hyp_reset goodbye, and use __hyp_reset_vectors.
Tested-by: NKeerthy <j-keerthy@ti.com>
Acked-by: NRussell King <rmk+kernel@armlinux.org.uk>
Acked-by: NCatalin Marinas <catalin.marinas@arm.com>
Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>
Signed-off-by: NChristoffer Dall <cdall@linaro.org>

We now have a full hyp-stub implementation in the KVM init code,
but the main KVM code only supports HVC_GET_VECTORS, which is not
enough.

Instead of reinventing the wheel, let's reuse the init implementation
by branching to the idmap page when called with a hyp-stub hypercall.
Tested-by: NKeerthy <j-keerthy@ti.com>
Acked-by: NRussell King <rmk+kernel@armlinux.org.uk>
Acked-by: NCatalin Marinas <catalin.marinas@arm.com>
Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>
Signed-off-by: NChristoffer Dall <cdall@linaro.org>

Now that we have an infrastructure to handle hypercalls in the KVM
init code, let's implement HVC_GET_VECTORS there.
Tested-by: NKeerthy <j-keerthy@ti.com>
Acked-by: NRussell King <rmk+kernel@armlinux.org.uk>
Acked-by: NCatalin Marinas <catalin.marinas@arm.com>
Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>
Signed-off-by: NChristoffer Dall <cdall@linaro.org>

In order to restore HYP mode to its original condition, KVM currently
implements __kvm_hyp_reset(). As we're moving towards a hyp-stub
defined API, it becomes necessary to implement HVC_RESET_VECTORS.

This patch adds the HVC_RESET_VECTORS hypercall to the KVM init
code, which so far lacked any form of hypercall support.
Tested-by: NKeerthy <j-keerthy@ti.com>
Acked-by: NRussell King <rmk+kernel@armlinux.org.uk>
Acked-by: NCatalin Marinas <catalin.marinas@arm.com>
Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>
Signed-off-by: NChristoffer Dall <cdall@linaro.org>

Let's define a new stub hypercall that resets the HYP configuration
to its default: hyp-stub vectors, and MMU disabled.

Of course, for the hyp-stub itself, this is a trivial no-op.
Hypervisors will have a bit more work to do.
Tested-by: NKeerthy <j-keerthy@ti.com>
Acked-by: NRussell King <rmk+kernel@armlinux.org.uk>
Acked-by: NCatalin Marinas <catalin.marinas@arm.com>
Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>
Signed-off-by: NChristoffer Dall <cdall@linaro.org>

Define a standard return value to be returned when a hyp stub
call fails.
Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>
Signed-off-by: NChristoffer Dall <cdall@linaro.org>

The KVM code needs to be able to compute the address of
symbols in its idmap page (the equivalent of a virt_to_idmap()
call). Unfortunately, virt_to_idmap is slightly complicated,
depending on the use of arch_phys_to_idmap_offset or not, and
none of that is readily available at HYP.

Instead, expose a single kimage_voffset variable which contains the
offset between a kernel VA and its idmap address, enabling the
VA->IDMAP conversion. This allows the KVM code to behave similarily
to its arm64 counterpart.
Tested-by: NKeerthy <j-keerthy@ti.com>
Acked-by: NRussell King <rmk+kernel@armlinux.org.uk>
Acked-by: NCatalin Marinas <catalin.marinas@arm.com>
Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>
Signed-off-by: NChristoffer Dall <cdall@linaro.org>

It is not really obvious why the restart address should be in r3
when communicated to the hyp-stub. r1 should be perfectly adequate,
and consistent with the rest of the code.
Tested-by: NKeerthy <j-keerthy@ti.com>
Acked-by: NRussell King <rmk+kernel@armlinux.org.uk>
Acked-by: NCatalin Marinas <catalin.marinas@arm.com>
Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>
Signed-off-by: NChristoffer Dall <cdall@linaro.org>

cpu_v7_reset() now takes a second parameter indicating whether
we should reboot in HYP or not. Update the documentation to
reflect this.
Tested-by: NKeerthy <j-keerthy@ti.com>
Acked-by: NRussell King <rmk+kernel@armlinux.org.uk>
Acked-by: NCatalin Marinas <catalin.marinas@arm.com>
Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>
Signed-off-by: NChristoffer Dall <cdall@linaro.org>

The conversion of the HYP stub ABI to something similar to arm64
left the KVM code broken, as it doesn't know about the new
stub numbering. Let's move the various #defines to virt.h, and
let KVM use HVC_GET_VECTORS.
Tested-by: NKeerthy <j-keerthy@ti.com>
Acked-by: NRussell King <rmk+kernel@armlinux.org.uk>
Acked-by: NCatalin Marinas <catalin.marinas@arm.com>
Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>
Signed-off-by: NChristoffer Dall <cdall@linaro.org>

When we soft-reboot (eg, kexec) from one kernel into the next, we need
to ensure that we enter the new kernel in the same processor mode as
when we were entered, so that (eg) the new kernel can install its own
hypervisor - the old kernel's hypervisor will have been overwritten.

In order to do this, we need to pass a flag to cpu_reset() so it knows
what to do, and we need to modify the kernel's own hypervisor stub to
allow it to handle a soft-reboot.

As we are always guaranteed to install our own hypervisor if we're
entered in HYP32 mode, and KVM will have moved itself out of the way
on kexec/normal reboot, we can assume that our hypervisor is in place
when we want to kexec, so changing our hypervisor API should not be a
problem.
Tested-by: NKeerthy <j-keerthy@ti.com>
Acked-by: NCatalin Marinas <catalin.marinas@arm.com>
Signed-off-by: NRussell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>
Signed-off-by: NChristoffer Dall <cdall@linaro.org>

Improve the hyp-stub ABI to allow it to do more than just get/set the
vectors.  We follow the example in ARM64, where r0 is used as an opcode
with the other registers as an argument.
Tested-by: NKeerthy <j-keerthy@ti.com>
Acked-by: NCatalin Marinas <catalin.marinas@arm.com>
Signed-off-by: NRussell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>
Signed-off-by: NChristoffer Dall <cdall@linaro.org>

Another missing stub hypercall is HVC_SOFT_RESTART. It turns out
that it is pretty easy to implement in terms of HVC_RESET_VECTORS
(since it needs to turn the MMU off).
Acked-by: NCatalin Marinas <catalin.marinas@arm.com>
Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>
Signed-off-by: NChristoffer Dall <cdall@linaro.org>

We are now able to use the hyp stub to reset HYP mode. Time to
kiss __kvm_hyp_reset goodbye, and use __hyp_reset_vectors.
Acked-by: NCatalin Marinas <catalin.marinas@arm.com>
Reviewed-by: NJames Morse <james.morse@arm.com>
Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>
Signed-off-by: NChristoffer Dall <cdall@linaro.org>

We now have a full hyp-stub implementation in the KVM init code,
but the main KVM code only supports HVC_GET_VECTORS, which is not
enough.

Instead of reinventing the wheel, let's reuse the init implementation
by branching to the idmap page when called with a hyp-stub hypercall.
Acked-by: NCatalin Marinas <catalin.marinas@arm.com>
Reviewed-by: NJames Morse <james.morse@arm.com>
Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>
Signed-off-by: NChristoffer Dall <cdall@linaro.org>

Now that we have an infrastructure to handle hypercalls in the KVM
init code, let's implement HVC_GET_VECTORS there.
Acked-by: NCatalin Marinas <catalin.marinas@arm.com>
Reviewed-by: NJames Morse <james.morse@arm.com>
Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>
Signed-off-by: NChristoffer Dall <cdall@linaro.org>

In order to restore HYP mode to its original condition, KVM currently
implements __kvm_hyp_reset(). As we're moving towards a hyp-stub
defined API, it becomes necessary to implement HVC_RESET_VECTORS.

This patch adds the HVC_RESET_VECTORS hypercall to the KVM init
code, which so far lacked any form of hypercall support.
Acked-by: NCatalin Marinas <catalin.marinas@arm.com>
Reviewed-by: NJames Morse <james.morse@arm.com>
Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>
Signed-off-by: NChristoffer Dall <cdall@linaro.org>

Let's define a new stub hypercall that resets the HYP configuration
to its default: hyp-stub vectors, and MMU disabled.

Of course, for the hyp-stub itself, this is a trivial no-op.
Hypervisors will have a bit more work to do.
Acked-by: NCatalin Marinas <catalin.marinas@arm.com>
Reviewed-by: NJames Morse <james.morse@arm.com>
Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>
Signed-off-by: NChristoffer Dall <cdall@linaro.org>

Comments in asm/virt.h are slightly out of date, so let's align
them with the new behaviour of the code.
Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>
Signed-off-by: NChristoffer Dall <cdall@linaro.org>

Define a standard return value to be returned when a hyp stub
call fails, and make KVM use it for ARM_EXCEPTION_HYP_GONE
(instead of using a KVM-specific value).
Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>
Signed-off-by: NChristoffer Dall <cdall@linaro.org>

The EL2 code is not corrupting lr anymore, so don't bother preserving
it in the EL1 trampoline code.
Acked-by: NCatalin Marinas <catalin.marinas@arm.com>
Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>
Signed-off-by: NChristoffer Dall <cdall@linaro.org>

At the moment, we only save/restore lr if on VHE, as we rely only
the EL1 code to have preserved it in the non-VHE case.

As we're about to get rid of the latter, let's move the save/restore
code to the do_el2_call macro, unifying both code paths.
Acked-by: NCatalin Marinas <catalin.marinas@arm.com>
Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>
Signed-off-by: NChristoffer Dall <cdall@linaro.org>

When entering the kernel hyp stub, we check whether or not we've
made it here through an HVC instruction, clobbering lr (aka x30)
in the process.

This is completely pointless, as HVC is the only way to get here
(all traps to EL2 are disabled, no interrupt override is applied).

So let's remove this bit of code whose only point is to corrupt
a valuable register.
Acked-by: NCatalin Marinas <catalin.marinas@arm.com>
Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>
Signed-off-by: NChristoffer Dall <cdall@linaro.org>

Instead of considering that a CP15 accessor has failed when
returning false, let's consider that it is *always* successful
(after all, we won't stand for an incomplete emulation).

The return value now simply indicates whether we should skip
the instruction (because it has now been emulated), or if we
should leave the PC alone if the emulation has injected an
exception.
Reviewed-by: NChristoffer Dall <cdall@linaro.org>
Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>

Reads from write-only system registers are generally confined to
EL1 and not propagated to EL2 (that's what the architecture
mantates). In order to be sure that we have a sane behaviour
even in the unlikely event that we have a broken system, we still
handle it in KVM. Same goes for write to RO registers.

In that case, let's inject an undef into the guest.
Reviewed-by: NChristoffer Dall <cdall@linaro.org>
Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>

If we fail to emulate a mrrc instruction, we:
1) deliver an exception,
2) spit a nastygram on the console,
3) write back some garbage to Rt/Rt2

While 1) and 2) are perfectly acceptable, 3) is out of the scope of
the architecture... Let's mimick the code in kvm_handle_cp_32 and
be more cautious.
Reviewed-by: NChristoffer Dall <cdall@linaro.org>
Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>
Signed-off-by: NChristoffer Dall <cdall@linaro.org>

Instead of considering that a sysreg accessor has failed when
returning false, let's consider that it is *always* successful
(after all, we won't stand for an incomplete emulation).

The return value now simply indicates whether we should skip
the instruction (because it has now been emulated), or if we
should leave the PC alone if the emulation has injected an
exception.
Reviewed-by: NChristoffer Dall <cdall@linaro.org>
Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>

PMSWINC_EL0 is a WO register, so let's UNDEF when reading from it
(in the highly hypothetical case where this doesn't UNDEF at EL1).
Reviewed-by: NChristoffer Dall <cdall@linaro.org>
Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>

Reads from write-only system registers are generally confined to
EL1 and not propagated to EL2 (that's what the architecture
mantates). In order to be sure that we have a sane behaviour
even in the unlikely event that we have a broken system, we still
handle it in KVM.

In that case, let's inject an undef into the guest.

Let's also remove write_to_read_only which isn't used anywhere.
Reviewed-by: NChristoffer Dall <cdall@linaro.org>
Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>