Re: [Xen-devel] Re: [PATCH 1/5] xen: events: use irq_alloc_desc(_at) instead of open-coding an IRQ allocator.

Jeremy Fitzhardinge
2010-10-26T20:20:45Z

On 10/26/2010 12:49 PM, Stefano Stabellini wrote:
> On Tue, 26 Oct 2010, Ian Campbell wrote:
>> On Mon, 2010-10-25 at 19:02 +0100, Ian Campbell wrote:
>>>
>>>> What do you see when you pass in a PCI device and say give the guest
>>> 32 CPUs??
>>>
>>> I can try tomorrow and see, based on what you say above without
>>> implementing what I described I suspect the answer will be "carnage".
>> Actually, it looks like multi-vcpu is broken, I only see 1 regardless of
>> how many I configured. It's not clear if this is breakage in Linus'
>> tree, something I pulled in from one of Jeremy's, yours or Stefano's
>> trees or some local pebcak. I'll investigate...
>
> I found the bug, it was introduced by:
>
> "xen: use vcpu_ops to setup cpu masks"
>
> I have added the fix at the end of my branch and I am also appending the
> fix here.

Acked.

J

> ---
>
>
> xen: initialize cpu masks for pv guests in xen_smp_init
>
> Pv guests don't have ACPI and need the cpu masks to be set
> correctly as early as possible so we call xen_fill_possible_map from
> xen_smp_init.
> On the other hand the initial domain supports ACPI so in this case we skip
> xen_fill_possible_map and rely on it. However Xen might limit the number
> of cpus usable by the domain, so we filter those masks during smp
> initialization using the VCPUOP_is_up hypercall.
> It is important that the filtering is done before
> xen_setup_vcpu_info_placement.
>
> Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
>
> diff --git a/arch/x86/xen/smp.c b/arch/x86/xen/smp.c
> index 1386767..834dfeb 100644
> --- a/arch/x86/xen/smp.c
> +++ b/arch/x86/xen/smp.c
> @@ -28,6 +28,7 @@
> #include <asm/xen/interface.h>
> #include <asm/xen/hypercall.h>
>
> +#include <xen/xen.h>
> #include <xen/page.h>
> #include <xen/events.h>
>
> @@ -156,6 +157,25 @@ static void __init xen_fill_possible_map(void)
> {
> int i, rc;
>
> + if (xen_initial_domain())
> + return;
> +
> + for (i = 0; i < nr_cpu_ids; i++) {
> + rc = HYPERVISOR_vcpu_op(VCPUOP_is_up, i, NULL);
> + if (rc >= 0) {
> + num_processors++;
> + set_cpu_possible(i, true);
> + }
> + }
> +}
> +
> +static void __init xen_filter_cpu_maps(void)
> +{
> + int i, rc;
> +
> + if (!xen_initial_domain())
> + return;
> +
> num_processors = 0;
> disabled_cpus = 0;
> for (i = 0; i < nr_cpu_ids; i++) {
> @@ -179,6 +199,7 @@ static void __init xen_smp_prepare_boot_cpu(void)
> old memory can be recycled */
> make_lowmem_page_readwrite(xen_initial_gdt);
>
> + xen_filter_cpu_maps();
> xen_setup_vcpu_info_placement();
> }
>
> @@ -195,8 +216,6 @@ static void __init xen_smp_prepare_cpus(unsigned int max_cpus)
> if (xen_smp_intr_init(0))
> BUG();
>
> - xen_fill_possible_map();
> -
> if (!alloc_cpumask_var(&xen_cpu_initialized_map, GFP_KERNEL))
> panic("could not allocate xen_cpu_initialized_map\n");
>
> @@ -487,5 +506,6 @@ static const struct smp_ops xen_smp_ops __initdata = {
> void __init xen_smp_init(void)
> {
> smp_ops = xen_smp_ops;
> + xen_fill_possible_map();
> xen_init_spinlocks();
> }
>