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[PATCH 1/3] xen/domain: Reorder trivial initialisation in early domain_create()

Andrew Cooper posted 3 patches 5 years, 1 month ago
[PATCH 1/3] xen/domain: Reorder trivial initialisation in early domain_create()
Posted by Andrew Cooper 5 years, 1 month ago 
This improves the robustness of the error paths.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
---
CC: Jan Beulich <JBeulich@suse.com>
CC: Roger Pau Monné <roger.pau@citrix.com>
CC: Wei Liu <wl@xen.org>
CC: Stefano Stabellini <sstabellini@kernel.org>
CC: Julien Grall <julien@xen.org>
CC: Volodymyr Babchuk <Volodymyr_Babchuk@epam.com>
---
 xen/common/domain.c | 41 ++++++++++++++++++++++-------------------
 1 file changed, 22 insertions(+), 19 deletions(-)

diff --git a/xen/common/domain.c b/xen/common/domain.c
index 5ec48c3e19..ce3667f1b4 100644
--- a/xen/common/domain.c
+++ b/xen/common/domain.c
@@ -391,25 +391,7 @@ struct domain *domain_create(domid_t domid,
 
     TRACE_1D(TRC_DOM0_DOM_ADD, d->domain_id);
 
-    /*
-     * Allocate d->vcpu[] and set ->max_vcpus up early.  Various per-domain
-     * resources want to be sized based on max_vcpus.
-     */
-    if ( !is_system_domain(d) )
-    {
-        err = -ENOMEM;
-        d->vcpu = xzalloc_array(struct vcpu *, config->max_vcpus);
-        if ( !d->vcpu )
-            goto fail;
-
-        d->max_vcpus = config->max_vcpus;
-    }
-
-    lock_profile_register_struct(LOCKPROF_TYPE_PERDOM, d, domid);
-
-    if ( (err = xsm_alloc_security_domain(d)) != 0 )
-        goto fail;
-
+    /* Trivial initialisation. */
     atomic_set(&d->refcnt, 1);
     RCU_READ_LOCK_INIT(&d->rcu_lock);
     spin_lock_init_prof(d, domain_lock);
@@ -434,6 +416,27 @@ struct domain *domain_create(domid_t domid,
     INIT_LIST_HEAD(&d->pdev_list);
 #endif
 
+    /* All error paths can depend on the above setup. */
+
+    /*
+     * Allocate d->vcpu[] and set ->max_vcpus up early.  Various per-domain
+     * resources want to be sized based on max_vcpus.
+     */
+    if ( !is_system_domain(d) )
+    {
+        err = -ENOMEM;
+        d->vcpu = xzalloc_array(struct vcpu *, config->max_vcpus);
+        if ( !d->vcpu )
+            goto fail;
+
+        d->max_vcpus = config->max_vcpus;
+    }
+
+    lock_profile_register_struct(LOCKPROF_TYPE_PERDOM, d, domid);
+
+    if ( (err = xsm_alloc_security_domain(d)) != 0 )
+        goto fail;
+
     err = -ENOMEM;
     if ( !zalloc_cpumask_var(&d->dirty_cpumask) )
         goto fail;
-- 
2.11.0
Re: [PATCH 1/3] xen/domain: Reorder trivial initialisation in early domain_create()
Posted by Jan Beulich 5 years, 1 month ago 
On 21.12.2020 19:14, Andrew Cooper wrote:
> --- a/xen/common/domain.c
> +++ b/xen/common/domain.c
> @@ -391,25 +391,7 @@ struct domain *domain_create(domid_t domid,
>  
>      TRACE_1D(TRC_DOM0_DOM_ADD, d->domain_id);
>  
> -    /*
> -     * Allocate d->vcpu[] and set ->max_vcpus up early.  Various per-domain
> -     * resources want to be sized based on max_vcpus.
> -     */
> -    if ( !is_system_domain(d) )
> -    {
> -        err = -ENOMEM;
> -        d->vcpu = xzalloc_array(struct vcpu *, config->max_vcpus);
> -        if ( !d->vcpu )
> -            goto fail;
> -
> -        d->max_vcpus = config->max_vcpus;
> -    }
> -
> -    lock_profile_register_struct(LOCKPROF_TYPE_PERDOM, d, domid);

Wouldn't this also count as "trivial initialization", and hence while
moving want to at least be placed ...

> -    if ( (err = xsm_alloc_security_domain(d)) != 0 )
> -        goto fail;
> -
> +    /* Trivial initialisation. */
>      atomic_set(&d->refcnt, 1);
>      RCU_READ_LOCK_INIT(&d->rcu_lock);
>      spin_lock_init_prof(d, domain_lock);
> @@ -434,6 +416,27 @@ struct domain *domain_create(domid_t domid,
>      INIT_LIST_HEAD(&d->pdev_list);
>  #endif
>  
> +    /* All error paths can depend on the above setup. */

... ahead of this comment?

> +    /*
> +     * Allocate d->vcpu[] and set ->max_vcpus up early.  Various per-domain
> +     * resources want to be sized based on max_vcpus.
> +     */
> +    if ( !is_system_domain(d) )
> +    {
> +        err = -ENOMEM;
> +        d->vcpu = xzalloc_array(struct vcpu *, config->max_vcpus);
> +        if ( !d->vcpu )
> +            goto fail;
> +
> +        d->max_vcpus = config->max_vcpus;
> +    }
> +
> +    lock_profile_register_struct(LOCKPROF_TYPE_PERDOM, d, domid);
> +
> +    if ( (err = xsm_alloc_security_domain(d)) != 0 )
> +        goto fail;
> +
>      err = -ENOMEM;
>      if ( !zalloc_cpumask_var(&d->dirty_cpumask) )
>          goto fail;
> 

Just as an observation (i.e. unlikely for this patch) I doubt
system domains need ->dirty_cpumask set up, and hence this
allocation may also want moving down a few lines.

Jan
Re: [PATCH 1/3] xen/domain: Reorder trivial initialisation in early domain_create()
Posted by Andrew Cooper 5 years, 1 month ago 
On 22/12/2020 10:10, Jan Beulich wrote:
> On 21.12.2020 19:14, Andrew Cooper wrote:
>> --- a/xen/common/domain.c
>> +++ b/xen/common/domain.c
>> @@ -391,25 +391,7 @@ struct domain *domain_create(domid_t domid,
>>  
>>      TRACE_1D(TRC_DOM0_DOM_ADD, d->domain_id);
>>  
>> -    /*
>> -     * Allocate d->vcpu[] and set ->max_vcpus up early.  Various per-domain
>> -     * resources want to be sized based on max_vcpus.
>> -     */
>> -    if ( !is_system_domain(d) )
>> -    {
>> -        err = -ENOMEM;
>> -        d->vcpu = xzalloc_array(struct vcpu *, config->max_vcpus);
>> -        if ( !d->vcpu )
>> -            goto fail;
>> -
>> -        d->max_vcpus = config->max_vcpus;
>> -    }
>> -
>> -    lock_profile_register_struct(LOCKPROF_TYPE_PERDOM, d, domid);
> Wouldn't this also count as "trivial initialization", and hence while
> moving want to at least be placed ...
>
>> -    if ( (err = xsm_alloc_security_domain(d)) != 0 )
>> -        goto fail;
>> -
>> +    /* Trivial initialisation. */
>>      atomic_set(&d->refcnt, 1);
>>      RCU_READ_LOCK_INIT(&d->rcu_lock);
>>      spin_lock_init_prof(d, domain_lock);
>> @@ -434,6 +416,27 @@ struct domain *domain_create(domid_t domid,
>>      INIT_LIST_HEAD(&d->pdev_list);
>>  #endif
>>  
>> +    /* All error paths can depend on the above setup. */
> ... ahead of this comment?

Can do.

>
>> +    /*
>> +     * Allocate d->vcpu[] and set ->max_vcpus up early.  Various per-domain
>> +     * resources want to be sized based on max_vcpus.
>> +     */
>> +    if ( !is_system_domain(d) )
>> +    {
>> +        err = -ENOMEM;
>> +        d->vcpu = xzalloc_array(struct vcpu *, config->max_vcpus);
>> +        if ( !d->vcpu )
>> +            goto fail;
>> +
>> +        d->max_vcpus = config->max_vcpus;
>> +    }
>> +
>> +    lock_profile_register_struct(LOCKPROF_TYPE_PERDOM, d, domid);
>> +
>> +    if ( (err = xsm_alloc_security_domain(d)) != 0 )
>> +        goto fail;
>> +
>>      err = -ENOMEM;
>>      if ( !zalloc_cpumask_var(&d->dirty_cpumask) )
>>          goto fail;
>>
> Just as an observation (i.e. unlikely for this patch) I doubt
> system domains need ->dirty_cpumask set up, and hence this
> allocation may also want moving down a few lines.

I agree in principle.  However, something does (or at least did)
reference this for system domains when I did the is_system_domain() cleanup.

The fix might not be as trivial as just moving the allocation.

~Andrew
Re: [PATCH 1/3] xen/domain: Reorder trivial initialisation in early domain_create()
Posted by Jan Beulich 5 years, 1 month ago 
On 22.12.2020 11:24, Andrew Cooper wrote:
> On 22/12/2020 10:10, Jan Beulich wrote:
>> On 21.12.2020 19:14, Andrew Cooper wrote:
>>> --- a/xen/common/domain.c
>>> +++ b/xen/common/domain.c
>>> @@ -391,25 +391,7 @@ struct domain *domain_create(domid_t domid,
>>>  
>>>      TRACE_1D(TRC_DOM0_DOM_ADD, d->domain_id);
>>>  
>>> -    /*
>>> -     * Allocate d->vcpu[] and set ->max_vcpus up early.  Various per-domain
>>> -     * resources want to be sized based on max_vcpus.
>>> -     */
>>> -    if ( !is_system_domain(d) )
>>> -    {
>>> -        err = -ENOMEM;
>>> -        d->vcpu = xzalloc_array(struct vcpu *, config->max_vcpus);
>>> -        if ( !d->vcpu )
>>> -            goto fail;
>>> -
>>> -        d->max_vcpus = config->max_vcpus;
>>> -    }
>>> -
>>> -    lock_profile_register_struct(LOCKPROF_TYPE_PERDOM, d, domid);
>> Wouldn't this also count as "trivial initialization", and hence while
>> moving want to at least be placed ...
>>
>>> -    if ( (err = xsm_alloc_security_domain(d)) != 0 )
>>> -        goto fail;
>>> -
>>> +    /* Trivial initialisation. */
>>>      atomic_set(&d->refcnt, 1);
>>>      RCU_READ_LOCK_INIT(&d->rcu_lock);
>>>      spin_lock_init_prof(d, domain_lock);
>>> @@ -434,6 +416,27 @@ struct domain *domain_create(domid_t domid,
>>>      INIT_LIST_HEAD(&d->pdev_list);
>>>  #endif
>>>  
>>> +    /* All error paths can depend on the above setup. */
>> ... ahead of this comment?
> 
> Can do.

At which point

Reviewed-by: Jan Beulich <jbeulich@suse.com>

Jan

Patchew 2.1-devel-b67e4c2

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