Re: [PATCH v2] hvf: arm: Ignore cache operations on MMIO

[Mark Kettenis]

> From: Alexander Graf <agraf@csgraf.de>
> Date: Tue, 26 Oct 2021 09:12:41 +0200
> 
> Apple's Hypervisor.Framework forwards cache operations as MMIO traps
> into user space. For MMIO however, these have no meaning: There is no
> cache attached to them.
> 
> So let's just treat cache data exits as nops.
> 
> This fixes OpenBSD booting as guest.
> 
> Signed-off-by: Alexander Graf <agraf@csgraf.de>
> Reported-by: AJ Barris <AwlsomeAlex@github.com>
> Reference: https://github.com/utmapp/UTM/issues/3197
> ---
>  target/arm/hvf/hvf.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/target/arm/hvf/hvf.c b/target/arm/hvf/hvf.c
> index bff3e0cde7..0dc96560d3 100644
> --- a/target/arm/hvf/hvf.c
> +++ b/target/arm/hvf/hvf.c
> @@ -1150,12 +1150,19 @@ int hvf_vcpu_exec(CPUState *cpu)
>          uint32_t sas = (syndrome >> 22) & 3;
>          uint32_t len = 1 << sas;
>          uint32_t srt = (syndrome >> 16) & 0x1f;
> +        uint32_t cm = (syndrome >> 8) & 0x1;
>          uint64_t val = 0;
>  
>          trace_hvf_data_abort(env->pc, hvf_exit->exception.virtual_address,
>                               hvf_exit->exception.physical_address, isv,
>                               iswrite, s1ptw, len, srt);
>  
> +        if (cm) {
> +            /* We don't cache MMIO regions */
> +            advance_pc = true;
> +            break;
> +        }
> +
>          assert(isv);
>  
>          if (iswrite) {
> -- 
> 2.30.1 (Apple Git-130)

Now that I see this diff, I think this is pretty much how I fixed it
when first trying your hvf patchset back in december/january.  Before
I lost the change because I accidentally wiped the disk...

Reviewed-by: Mark Kettenis <kettenis@openbsd.org>