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

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Message-ID: <4CC73816.50108@goop.org>
Date:	Tue, 26 Oct 2010 13:20:38 -0700
From:	Jeremy Fitzhardinge <jeremy@...p.org>
To:	Stefano Stabellini <stefano.stabellini@...citrix.com>
CC:	Ian Campbell <Ian.Campbell@...citrix.com>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	"xen-devel@...ts.xensource.com" <xen-devel@...ts.xensource.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"H. Peter Anvin" <hpa@...or.com>, "mingo@...e.hu" <mingo@...e.hu>,
	"tglx@...utronix.de" <tglx@...utronix.de>
Subject: Re: [Xen-devel] Re: [PATCH 1/5] xen: events: use irq_alloc_desc(_at)
 instead of open-coding an IRQ allocator.

 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@...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();
>  }
>

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