Re: [Qemu-ppc] [PATCH] spapr/xive: Sanity checks of OV5 during CAS

[Satheesh Rajendran]

On Wed, May 15, 2019 at 07:04:24PM +0200, Greg Kurz wrote:
> If a machine is started with ic-mode=xive but the guest only knows
> about XICS, eg. an RHEL 7.6 guest, the kernel panics. This is
> expected but a bit unfortunate since the crash doesn't provide
> much information for the end user to guess what's happening.
> 
> Detect that during CAS and exit QEMU with a proper error message
> instead, like it is already done for the MMU.
> 
> Even if this is less likely to happen, the opposite case of a guest
> that only knows about XIVE would certainly fail all the same if the
> machine is started with ic-mode=xics.
> 
> Also, the only valid values a guest can pass in byte 23 of OV5 during
> CAS are 0b00 (XIVE legacy mode) and 0b01 (XIVE exploitation mode). Any
> other value is a bug, at least with the current spec. Again, it does
> not seem right to let the guest go on without a precise idea of the
> interrupt mode it asked for.
> 
> Handle these cases as well.
> 
> Reported-by: Satheesh Rajendran <address@hidden>
> Signed-off-by: Greg Kurz <address@hidden>
> ---
>  hw/ppc/spapr_hcall.c |   24 ++++++++++++++++++++++++
>  1 file changed, 24 insertions(+)
> 
> diff --git a/hw/ppc/spapr_hcall.c b/hw/ppc/spapr_hcall.c
> index 6c16d2b12040..63a55614b83d 100644
> --- a/hw/ppc/spapr_hcall.c
> +++ b/hw/ppc/spapr_hcall.c
> @@ -1513,6 +1513,7 @@ static target_ulong 
> h_client_architecture_support(PowerPCCPU *cpu,
>      bool guest_radix;
>      Error *local_err = NULL;
>      bool raw_mode_supported = false;
> +    bool guest_xive;
> 
>      cas_pvr = cas_check_pvr(spapr, cpu, &addr, &raw_mode_supported, 
> &local_err);
>      if (local_err) {
> @@ -1545,10 +1546,17 @@ static target_ulong 
> h_client_architecture_support(PowerPCCPU *cpu,
>          error_report("guest requested hash and radix MMU, which is 
> invalid.");
>          exit(EXIT_FAILURE);
>      }
> +    if (spapr_ovec_test(ov5_guest, OV5_XIVE_BOTH)) {
> +        error_report("guest requested an invalid interrupt mode");
> +        exit(EXIT_FAILURE);
> +    }
> +
>      /* The radix/hash bit in byte 24 requires special handling: */
>      guest_radix = spapr_ovec_test(ov5_guest, OV5_MMU_RADIX_300);
>      spapr_ovec_clear(ov5_guest, OV5_MMU_RADIX_300);
> 
> +    guest_xive = spapr_ovec_test(ov5_guest, OV5_XIVE_EXPLOIT);
> +
>      /*
>       * HPT resizing is a bit of a special case, because when enabled
>       * we assume an HPT guest will support it until it says it
> @@ -1632,6 +1640,22 @@ static target_ulong 
> h_client_architecture_support(PowerPCCPU *cpu,
>                                            ov5_updates) != 0);
>      }
> 
> +    /*
> +     * Ensure the guest asks for an interrupt mode we support; otherwise
> +     * terminate the boot.
> +     */
> +    if (guest_xive) {
> +        if (spapr->irq->ov5 == SPAPR_OV5_XIVE_LEGACY) {
> +            error_report("Guest requested unavailable interrupt mode 
> (XIVE)");
> +            exit(EXIT_FAILURE);
> +        }
> +    } else {
> +        if (spapr->irq->ov5 == SPAPR_OV5_XIVE_EXPLOIT) {
> +            error_report("Guest requested unavailable interrupt mode 
> (XICS)");

Looks like there is a typo in the error msg reported, instead it should be 
something like below

"Guest requested unavailable interrupt mode(XIVE), please use supported 
interrupt mode(ic-type=xics)"

Same for the previous check aswell.

Coz, I booted 3.10(kernel) guest with ic-type=xive and got a below error, which 
seems wrong

2019-05-16T06:24:58.713261Z qemu-system-ppc64: Guest requested unavailable 
interrupt mode (XICS)

Regards,
-Satheesh.

> +            exit(EXIT_FAILURE);
> +        }
> +    }
> +
>      /*
>       * Generate a machine reset when we have an update of the
>       * interrupt mode. Only required when the machine supports both
>