Re: [Qemu-devel] [PATCH] arm: virt-acpi: each MADT.GICC entry as enabled unconditionally

[Shannon Zhao]

On 2016/1/29 22:24, Igor Mammedov wrote:
> in current impl. condition
>
> build_madt() {
>    ...
>    if (test_bit(i, cpuinfo->found_cpus))
>
> is always true since loop handles only present CPUs
> in range [0..smp_cpus).
> But to fill usless cpuinfo->found_cpus we do unnecessary
> scan over QOM tree to find the same CPUs.
> So mark GICC as present always and drop not needed
> code that fills cpuinfo->found_cpus.
>
> Signed-off-by: Igor Mammedov<address@hidden>
> ---
> It's just simple cleanup but I'm trying to generalize
> a bit CPU related ACPI tables and as part of it get rid
> of found_cpus bitmap and if possible cpu_index usage
> in ACPI parts of code.
> ---
>   hw/arm/virt-acpi-build.c | 26 +++-----------------------
>   1 file changed, 3 insertions(+), 23 deletions(-)
>
> diff --git a/hw/arm/virt-acpi-build.c b/hw/arm/virt-acpi-build.c
> index 87fbe7c..3ed39fc 100644
> --- a/hw/arm/virt-acpi-build.c
> +++ b/hw/arm/virt-acpi-build.c
> @@ -46,20 +46,6 @@
>   #define ARM_SPI_BASE 32
>   #define ACPI_POWER_BUTTON_DEVICE "PWRB"
>
> -typedef struct VirtAcpiCpuInfo {
> -    DECLARE_BITMAP(found_cpus, VIRT_ACPI_CPU_ID_LIMIT);
> -} VirtAcpiCpuInfo;
> -
> -static void virt_acpi_get_cpu_info(VirtAcpiCpuInfo *cpuinfo)
> -{
> -    CPUState *cpu;
> -
> -    memset(cpuinfo->found_cpus, 0, sizeof cpuinfo->found_cpus);
> -    CPU_FOREACH(cpu) {
> -        set_bit(cpu->cpu_index, cpuinfo->found_cpus);
> -    }
> -}
> -
>   static void acpi_dsdt_add_cpus(Aml *scope, int smp_cpus)
>   {
>       uint16_t i;
> @@ -458,8 +444,7 @@ build_gtdt(GArray *table_data, GArray *linker)
>
>   /* MADT */
>   static void
> -build_madt(GArray *table_data, GArray *linker, VirtGuestInfo *guest_info,
> -           VirtAcpiCpuInfo *cpuinfo)
> +build_madt(GArray *table_data, GArray *linker, VirtGuestInfo *guest_info)
>   {
>       int madt_start = table_data->len;
>       const MemMapEntry *memmap = guest_info->memmap;
> @@ -489,9 +474,7 @@ build_madt(GArray *table_data, GArray *linker, 
> VirtGuestInfo *guest_info,
>           gicc->cpu_interface_number = i;
>           gicc->arm_mpidr = armcpu->mp_affinity;
>           gicc->uid = i;
> -        if (test_bit(i, cpuinfo->found_cpus)) {
> -            gicc->flags = cpu_to_le32(ACPI_GICC_ENABLED);
> -        }
> +        gicc->flags = cpu_to_le32(ACPI_GICC_ENABLED);
>       }
Ah, yes, it uses smp_cpus not max_cpus. But we still needs to support 
max_cpus usage even though it doesn't support vcpu hotplug currently. So 
we may need to introduce guest_info->max_cpus and use it here.
And below check in virt.c is not right while it should compare the 
global max_cpus with the max_cpus GIC supports.

    if (smp_cpus > max_cpus) {
        error_report("Number of SMP CPUs requested (%d) exceeds max CPUs "
                     "supported by machine 'mach-virt' (%d)",
                     smp_cpus, max_cpus);
        exit(1);
    }

Thanks,
--
Shannon