[PATCH v6 07/13] KVM: arm/arm64: mask/unmask daif around VHE guests

[Marc Zyngier]

On 15/01/18 19:39, James Morse wrote:
> Non-VHE systems take an exception to EL2 in order to world-switch into the
> guest. When returning from the guest KVM implicitly restores the DAIF
> flags when it returns to the kernel at EL1.
> 
> With VHE none of this exception-level jumping happens, so KVMs
> world-switch code is exposed to the host kernel's DAIF values, and KVM
> spills the guest-exit DAIF values back into the host kernel.
> On entry to a guest we have Debug and SError exceptions unmasked, KVM
> has switched VBAR but isn't prepared to handle these. On guest exit
> Debug exceptions are left disabled once we return to the host and will
> stay this way until we enter user space.
> 
> Add a helper to mask/unmask DAIF around VHE guests. The unmask can only
> happen after the hosts VBAR value has been synchronised by the isb in
> __vhe_hyp_call (via kvm_call_hyp()). Masking could be as late as
> setting KVMs VBAR value, but is kept here for symmetry.
> 
> Signed-off-by: James Morse <james.morse at arm.com>
> Reviewed-by: Christoffer Dall <christoffer.dall at linaro.org>

Acked-by: Marc Zyngier <marc.zyngier at arm.com>

	M.
-- 
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