Re: [PULL 35/38] spapr: nested: Introduce H_GUEST_[GET|SET]_STATE hcalls.

[Peter Maydell]

On Tue, 12 Mar 2024 at 17:11, Nicholas Piggin <npiggin@gmail.com> wrote:
>
> From: Harsh Prateek Bora <harshpb@linux.ibm.com>
>
> Introduce the nested PAPR hcalls:
>     - H_GUEST_GET_STATE which is used to get state of a nested guest or
>       a guest VCPU. The value field for each element in the request is
>       destination to be updated to reflect current state on success.
>     - H_GUEST_SET_STATE which is used to modify the state of a guest or
>       a guest VCPU. On success, guest (or its VCPU) state shall be
>       updated as per the value field for the requested element(s).
>
> Reviewed-by: Nicholas Piggin <npiggin@gmail.com>
> Signed-off-by: Michael Neuling <mikey@neuling.org>
> Signed-off-by: Harsh Prateek Bora <harshpb@linux.ibm.com>
> Signed-off-by: Nicholas Piggin <npiggin@gmail.com>

Hi; Coverity points out a problem with this code (CID 1540008, 1540009):



> +static target_ulong h_guest_getset_state(PowerPCCPU *cpu,
> +                                         SpaprMachineState *spapr,
> +                                         target_ulong *args,
> +                                         bool set)
> +{
> +    target_ulong flags = args[0];
> +    target_ulong lpid = args[1];
> +    target_ulong vcpuid = args[2];
> +    target_ulong buf = args[3];
> +    target_ulong buflen = args[4];
> +    struct guest_state_request gsr;
> +    SpaprMachineStateNestedGuest *guest;
> +
> +    guest = spapr_get_nested_guest(spapr, lpid);
> +    if (!guest) {
> +        return H_P2;
> +    }
> +    gsr.buf = buf;
> +    assert(buflen <= GSB_MAX_BUF_SIZE);
> +    gsr.len = buflen;
> +    gsr.flags = 0;
> +    if (flags & H_GUEST_GETSET_STATE_FLAG_GUEST_WIDE) {

flags is a target_ulong, which means it might only be 32 bits.
But H_GUEST_GETSET_STATE_FLAG_GUEST_WIDE has a bit set in the
upper 32 bits only. So Coverity complains about this condition
being always-zero and the body of the if being dead code.

What was the intention here?

> +        gsr.flags |= GUEST_STATE_REQUEST_GUEST_WIDE;
> +    }
> +    if (flags & !H_GUEST_GETSET_STATE_FLAG_GUEST_WIDE) {
> +        return H_PARAMETER; /* flag not supported yet */
> +    }
> +
> +    if (set) {
> +        gsr.flags |= GUEST_STATE_REQUEST_SET;
> +    }
> +    return map_and_getset_state(cpu, guest, vcpuid, &gsr);
> +}

thanks
-- PMM