On Fri, 6 May 2022 15:37:55 +1000, Alexey Kardashevskiy wrote:
> LoPAPR defines guest visible IOMMU with hypercalls to use it -
> H_PUT_TCE/etc. Implemented first on POWER7 where hypercalls would trap
> in the KVM in the real mode (with MMU off). The problem with the real mode
> is some memory is not available and some API usage crashed the host but
> enabling MMU was an expensive operation.
>
> The problems with the real mode handlers are:
> 1. Occasionally these cannot complete the request so the code is
> copied+modified to work in the virtual mode, very little is shared;
> 2. The real mode handlers have to be linked into vmlinux to work;
> 3. An exception in real mode immediately reboots the machine.
>
> [...]
Applied to powerpc/topic/ppc-kvm.
[1/1] KVM: PPC: Book3s: Retire H_PUT_TCE/etc real mode handlers
https://git.kernel.org/powerpc/c/cad32d9d42e8e6a659786f8a730b221a9fbee227
cheers
