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Re: [libvirt] [PATCH] xen: work with ia64 MAX_VIRT_CPUS of 64



On 11/01/2010 10:35 AM, Daniel P. Berrange wrote:
> On Fri, Oct 29, 2010 at 11:19:50AM -0600, Eric Blake wrote:
>> diff --git a/src/xen/xend_internal.c b/src/xen/xend_internal.c
>> index 974e96b..614c036 100644
>> --- a/src/xen/xend_internal.c
>> +++ b/src/xen/xend_internal.c
>> @@ -5770,10 +5770,11 @@ xenDaemonFormatSxpr(virConnectPtr conn,
>>      virBufferVSprintf(&buf, "(memory %lu)(maxmem %lu)",
>>                        def->mem.cur_balloon/1024, def->mem.max_balloon/1024);
>>      virBufferVSprintf(&buf, "(vcpus %u)", def->maxvcpus);
>> -    /* Computing the vcpu_avail bitmask works because MAX_VIRT_CPUS is 32.  */
>> -    verify(MAX_VIRT_CPUS <= sizeof(1U) * CHAR_BIT);
>> +    /* Computing the vcpu_avail bitmask works because MAX_VIRT_CPUS is
>> +       either 32, or 64 on a platform where long is big enough.  */
>> +    verify(MAX_VIRT_CPUS <= sizeof(1UL) * CHAR_BIT);
>>      if (def->vcpus < def->maxvcpus)
>> -        virBufferVSprintf(&buf, "(vcpu_avail %u)", (1U << def->vcpus) - 1);
>> +        virBufferVSprintf(&buf, "(vcpu_avail %lu)", (1UL << def->vcpus) - 1);
>>
>>      if (def->cpumask) {
>>          char *ranges = virDomainCpuSetFormat(def->cpumask, def->cpumasklen);
> 
> This chunk causes a compile error for me
> 
>   CC     libvirt_driver_xen_la-xend_internal.lo
> cc1: warnings being treated as errors
> xen/xend_internal.c: In function 'xenDaemonFormatSxpr':
> xen/xend_internal.c:5775: error: nested extern declaration of 'verify_function2' [-Wnested-externs]
> make[3]: *** [libvirt_driver_xen_la-xend_internal.lo] Error 1

Which version of gcc?  This may be a bug in gnulib's verify module.  I
tested successfully on F13, gcc 4.4.4.

> 
> 
> Also, what was commited, looks different to this diff here
> 
> @@ -5770,9 +5770,11 @@ xenDaemonFormatSxpr(virConnectPtr conn,
>      virBufferVSprintf(&buf, "(memory %lu)(maxmem %lu)",
>                        def->mem.cur_balloon/1024, def->mem.max_balloon/1024);
>      virBufferVSprintf(&buf, "(vcpus %u)", def->maxvcpus);
> -    /* Computing the vcpu_avail bitmask works because MAX_VIRT_CPUS is 32.  */
> +    /* Computing the vcpu_avail bitmask works because MAX_VIRT_CPUS is
> +       either 32, or 64 on a platform where long is big enough.  */
> +    verify(MAX_VIRT_CPUS <= sizeof(1UL) * CHAR_BIT);
>      if (def->vcpus < def->maxvcpus)
> -        virBufferVSprintf(&buf, "(vcpu_avail %u)", (1U << def->vcpus) - 1);
> +        virBufferVSprintf(&buf, "(vcpu_avail %lu)", (1UL << def->vcpus) - 1);

As Diego pointed out, the diff posted to this list was incomplete; it
was a partial patch that I had forgotten to squash in to my first
attempt.  What I actually pushed was both patches squashed together; for
reference, here's what the first patch was:

From b67847f84d9d4e8dbad5200df247212bc14221ab Mon Sep 17 00:00:00 2001
From: Eric Blake <eblake redhat com>
Date: Fri, 29 Oct 2010 10:51:01 -0600
Subject: [PATCH] xen: verify code assumption about MAX_VIRT_CPUS

* src/xen/xend_internal.c (xenDaemonFormatSxpr): Detect if
upstream xen ever changes to support 64 vcpus.
* src/xen/xm_internal.c (xenXMDomainConfigFormat): Likewise.
---
 src/xen/xend_internal.c |    1 +
 src/xen/xm_internal.c   |    2 ++
 2 files changed, 3 insertions(+), 0 deletions(-)

diff --git a/src/xen/xend_internal.c b/src/xen/xend_internal.c
index e96b762..974e96b 100644
--- a/src/xen/xend_internal.c
+++ b/src/xen/xend_internal.c
@@ -5771,6 +5771,7 @@ xenDaemonFormatSxpr(virConnectPtr conn,
                       def->mem.cur_balloon/1024,
def->mem.max_balloon/1024);
     virBufferVSprintf(&buf, "(vcpus %u)", def->maxvcpus);
     /* Computing the vcpu_avail bitmask works because MAX_VIRT_CPUS is
32.  */
+    verify(MAX_VIRT_CPUS <= sizeof(1U) * CHAR_BIT);
     if (def->vcpus < def->maxvcpus)
         virBufferVSprintf(&buf, "(vcpu_avail %u)", (1U << def->vcpus) - 1);

diff --git a/src/xen/xm_internal.c b/src/xen/xm_internal.c
index 430d40b..f80e252 100644
--- a/src/xen/xm_internal.c
+++ b/src/xen/xm_internal.c
@@ -2336,6 +2336,8 @@ virConfPtr xenXMDomainConfigFormat(virConnectPtr conn,

     if (xenXMConfigSetInt(conf, "vcpus", def->maxvcpus) < 0)
         goto no_memory;
+    /* Computing the vcpu_avail bitmask works because MAX_VIRT_CPUS is
32.  */
+    verify(MAX_VIRT_CPUS <= sizeof(1U) * CHAR_BIT);
     if (def->vcpus < def->maxvcpus &&
         xenXMConfigSetInt(conf, "vcpu_avail", (1U << def->vcpus) - 1) < 0)
         goto no_memory;
-- 
1.7.2.3



-- 
Eric Blake   eblake redhat com    +1-801-349-2682
Libvirt virtualization library http://libvirt.org

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