Re: [RFC PATCH v0 1/2] spapr: Add H_REG_SNS hcall

[Fabiano Rosas <farosas@linux.ibm.com>]

Bharata B Rao <bharata@linux.ibm.com> writes:

> Add support for H_REG_SNS hcall so that asynchronous page
> fault mechanism can be supported on PowerKVM guests.
>
> This hcall essentially issues KVM_PPC_SET_SNS to let the
> host map and pin the memory containing the Subvention
> Notification Structure. It also claims SPAPR_IRQ_SNS to
> be used as subvention notification interrupt.
>
> Note: Updates to linux-headers/linux/kvm.h are temporary
> pending headers update.
>
> Signed-off-by: Bharata B Rao <bharata@linux.ibm.com>

...

> +static target_ulong h_reg_sns(PowerPCCPU *cpu, SpaprMachineState *spapr,
> +                              target_ulong opcode, target_ulong *args)
> +{
> +    target_ulong addr = args[0];
> +    target_ulong len = args[1];
> +
> +    if (addr == -1) {
> +        return deregister_sns(cpu, spapr);
> +    }
> +
> +    /*
> +     * If SNS area is already registered, can't register again before
> +     * deregistering it first.
> +     */
> +    if (spapr->sns_addr == -1) {
> +        return H_PARAMETER;
> +    }

Don't you mean (spapr->sns_addr != -1) ?

> +
> +    if (!QEMU_IS_ALIGNED(addr, 4096)) {
> +        return H_PARAMETER;
> +    }
> +
> +    if (len < 256) {
> +        return H_P2;
> +    }
> +
> +    /* TODO: SNS area is not allowed to cross a page boundary */
> +
> +    /* KVM_PPC_SET_SNS ioctl */
> +    if (kvmppc_set_sns_reg(addr, len)) {
> +        return H_PARAMETER;
> +    }
> +
> +    /* Record SNS addr and len */
> +    spapr->sns_addr = addr;
> +    spapr->sns_len = len;
> +
> +    /* Register irq source for sending ESN notification */
> +    spapr_irq_claim(spapr, SPAPR_IRQ_SNS, false, &error_fatal);
> +    args[1] = SPAPR_IRQ_SNS; /* irq no in R5 */
> +
> +    return H_SUCCESS;
> +}