David Vrabel
2012-Sep-10 17:26 UTC
[PATCH] x86: make the dom0_max_vcpus option more flexible
From: David Vrabel <david.vrabel@citrix.com>
The dom0_max_vcpus command line option only allows the exact number of
VCPUs for dom0 to be set. It is not possible to say "up to N VCPUs
but no more than the number physically present."
Allow a range for the option to set a minimum number of VCPUs, and a
maximum which does not exceed the number of PCPUs.
For example, with "dom0_max_vcpus=4-8":
PCPUs Dom0 VCPUs
2 4
4 4
6 6
8 8
10 8
Existing command lines with "dom0_max_vcpus=N" still work as before
(and are equivalent to dom0_max_vcpus=N-N).
Signed-off-by: David Vrabel <david.vrabel@citrix.com>
Acked-by: Jan Beulich <jbeulich@suse.com>
---
Changes since v2:
- none, repost for Xen 4.3
---
docs/misc/xen-command-line.markdown | 29 +++++++++++++++++++++--
xen/arch/x86/domain_build.c | 43 +++++++++++++++++++++++++---------
2 files changed, 57 insertions(+), 15 deletions(-)
diff --git a/docs/misc/xen-command-line.markdown
b/docs/misc/xen-command-line.markdown
index 6599931..97a2bb2 100644
--- a/docs/misc/xen-command-line.markdown
+++ b/docs/misc/xen-command-line.markdown
@@ -383,10 +383,33 @@ Specify the bit width of the DMA heap.
Specify a list of IO ports to be excluded from dom0 access.
### dom0\_max\_vcpus
-> `= <integer>`
-Specify the maximum number of vcpus to give to dom0. This defaults
-to the number of pcpus on the host.
+Either:
+
+> `= <integer>`.
+
+The number of VCPUs to give to dom0. This number of VCPUs can be more
+than the number of PCPUs on the host. The default is the number of
+PCPUs.
+
+Or:
+
+> `= <min>-<max>` where `<min>` and `<max>` are
integers.
+
+Gives dom0 a number of VCPUs equal to the number of PCPUs, but always
+at least `<min>` and no more than `<max>`. Using `<min>` may
give
+more VCPUs than PCPUs. `<min>` or `<max>` may be omitted and the
+defaults of 1 and unlimited respectively are used instead.
+
+For example, with `dom0_max_vcpus=4-8`:
+
+ Number of
+ PCPUs | Dom0 VCPUs
+ 2 | 4
+ 4 | 4
+ 6 | 6
+ 8 | 8
+ 10 | 8
### dom0\_mem
> `= List of ( min:<size> | max:<size> | <size> )`
diff --git a/xen/arch/x86/domain_build.c b/xen/arch/x86/domain_build.c
index b3c5d4c..686b626 100644
--- a/xen/arch/x86/domain_build.c
+++ b/xen/arch/x86/domain_build.c
@@ -82,20 +82,39 @@ static void __init parse_dom0_mem(const char *s)
}
custom_param("dom0_mem", parse_dom0_mem);
-static unsigned int __initdata opt_dom0_max_vcpus;
-integer_param("dom0_max_vcpus", opt_dom0_max_vcpus);
+static unsigned int __initdata opt_dom0_max_vcpus_min = 1;
+static unsigned int __initdata opt_dom0_max_vcpus_max = UINT_MAX;
+
+static void __init parse_dom0_max_vcpus(const char *s)
+{
+ if (*s == ''-'') /* -M */
+ opt_dom0_max_vcpus_max = simple_strtoul(s + 1, &s, 0);
+ else { /* N, N-, or N-M */
+ opt_dom0_max_vcpus_min = simple_strtoul(s, &s, 0);
+ if (*s++ == ''\0'') /* N */
+ opt_dom0_max_vcpus_max = opt_dom0_max_vcpus_min;
+ else if (*s != ''\0'') /* N-M */
+ opt_dom0_max_vcpus_max = simple_strtoul(s, &s, 0);
+ }
+}
+custom_param("dom0_max_vcpus", parse_dom0_max_vcpus);
struct vcpu *__init alloc_dom0_vcpu0(void)
{
- if ( opt_dom0_max_vcpus == 0 )
- opt_dom0_max_vcpus = num_cpupool_cpus(cpupool0);
- if ( opt_dom0_max_vcpus > MAX_VIRT_CPUS )
- opt_dom0_max_vcpus = MAX_VIRT_CPUS;
+ unsigned max_vcpus;
+
+ max_vcpus = num_cpupool_cpus(cpupool0);
+ if ( opt_dom0_max_vcpus_min > max_vcpus )
+ max_vcpus = opt_dom0_max_vcpus_min;
+ if ( opt_dom0_max_vcpus_max < max_vcpus )
+ max_vcpus = opt_dom0_max_vcpus_max;
+ if ( max_vcpus > MAX_VIRT_CPUS )
+ max_vcpus = MAX_VIRT_CPUS;
- dom0->vcpu = xzalloc_array(struct vcpu *, opt_dom0_max_vcpus);
+ dom0->vcpu = xzalloc_array(struct vcpu *, max_vcpus);
if ( !dom0->vcpu )
return NULL;
- dom0->max_vcpus = opt_dom0_max_vcpus;
+ dom0->max_vcpus = max_vcpus;
return alloc_vcpu(dom0, 0, 0);
}
@@ -185,11 +204,11 @@ static unsigned long __init compute_dom0_nr_pages(
unsigned long max_pages = dom0_max_nrpages;
/* Reserve memory for further dom0 vcpu-struct allocations... */
- avail -= (opt_dom0_max_vcpus - 1UL)
+ avail -= (d->max_vcpus - 1UL)
<< get_order_from_bytes(sizeof(struct vcpu));
/* ...and compat_l4''s, if needed. */
if ( is_pv_32on64_domain(d) )
- avail -= opt_dom0_max_vcpus - 1;
+ avail -= d->max_vcpus - 1;
/* Reserve memory for iommu_dom0_init() (rough estimate). */
if ( iommu_enabled )
@@ -883,10 +902,10 @@ int __init construct_dom0(
for ( i = 0; i < XEN_LEGACY_MAX_VCPUS; i++ )
shared_info(d, vcpu_info[i].evtchn_upcall_mask) = 1;
- printk("Dom0 has maximum %u VCPUs\n", opt_dom0_max_vcpus);
+ printk("Dom0 has maximum %u VCPUs\n", d->max_vcpus);
cpu = cpumask_first(cpupool0->cpu_valid);
- for ( i = 1; i < opt_dom0_max_vcpus; i++ )
+ for ( i = 1; i < d->max_vcpus; i++ )
{
cpu = cpumask_cycle(cpu, cpupool0->cpu_valid);
(void)alloc_vcpu(d, i, cpu);
--
1.7.2.5
Jan Beulich
2012-Sep-11 07:05 UTC
Re: [PATCH] x86: make the dom0_max_vcpus option more flexible
>>> On 10.09.12 at 19:26, David Vrabel <david.vrabel@citrix.com> wrote: > From: David Vrabel <david.vrabel@citrix.com> > > The dom0_max_vcpus command line option only allows the exact number of > VCPUs for dom0 to be set. It is not possible to say "up to N VCPUs > but no more than the number physically present." > > Allow a range for the option to set a minimum number of VCPUs, and a > maximum which does not exceed the number of PCPUs. > > For example, with "dom0_max_vcpus=4-8": > > PCPUs Dom0 VCPUs > 2 4 > 4 4 > 6 6 > 8 8 > 10 8 > > Existing command lines with "dom0_max_vcpus=N" still work as before > (and are equivalent to dom0_max_vcpus=N-N). > > Signed-off-by: David Vrabel <david.vrabel@citrix.com> > Acked-by: Jan Beulich <jbeulich@suse.com> > --- > Changes since v2: > - none, repost for Xen 4.3Thanks for resending - it didn''t get lost, just didn''t get around to apply it yet as I first wanted to have it in my local tree for a short while. Jan