[PATCH] x86/iommu: account for necessary allocations when calculating Dom0's initial allocation size

[PATCH] x86/iommu: account for necessary allocations when calculating Dom0's initial allocation size

[Jan Beulich]

[-- Attachment #1: Type: text/plain, Size: 1188 bytes --]

As of c/s 21812:e382656e4dcc, IOMMU related allocations for Dom0
happen only after it got all of its memory allocated, and hence the
reserve (mainly for setting up its swiotlb) may get exhausted without
accounting for the necessary allocations up front.

While not precise, the estimate has been found to be within a couple
of pages for the systems it got tested on.

For the calculation to be reasonably correct, this depends on the
patch titled "x86/iommu: don't map RAM holes above 4G" sent out
yesterday.

Signed-off-by: Jan Beulich <jbeulich@novell.com>

--- a/xen/arch/x86/domain_build.c
+++ b/xen/arch/x86/domain_build.c
@@ -191,6 +191,15 @@ static unsigned long __init compute_dom0
     if ( is_pv_32on64_domain(d) )
         avail -= opt_dom0_max_vcpus - 1;
 
+    /* Reserve memory for iommu_dom0_init() (rough estimate). */
+    if ( iommu_enabled )
+    {
+        unsigned int s;
+
+        for ( s = 9; s < BITS_PER_LONG; s += 9 )
+            avail -= max_pdx >> s;
+    }
+
     /*
      * If domain 0 allocation isn't specified, reserve 1/16th of available
      * memory for things like DMA buffers. This reservation is clamped to 




[-- Attachment #2: x86-iommu-dom0-estimate.patch --]
[-- Type: text/plain, Size: 1182 bytes --]

As of c/s 21812:e382656e4dcc, IOMMU related allocations for Dom0
happen only after it got all of its memory allocated, and hence the
reserve (mainly for setting up its swiotlb) may get exhausted without
accounting for the necessary allocations up front.

While not precise, the estimate has been found to be within a couple
of pages for the systems it got tested on.

For the calculation to be reasonably correct, this depends on the
patch titled "x86/iommu: don't map RAM holes above 4G" sent out
yesterday.

Signed-off-by: Jan Beulich <jbeulich@novell.com>

--- a/xen/arch/x86/domain_build.c
+++ b/xen/arch/x86/domain_build.c
@@ -191,6 +191,15 @@ static unsigned long __init compute_dom0
     if ( is_pv_32on64_domain(d) )
         avail -= opt_dom0_max_vcpus - 1;
 
+    /* Reserve memory for iommu_dom0_init() (rough estimate). */
+    if ( iommu_enabled )
+    {
+        unsigned int s;
+
+        for ( s = 9; s < BITS_PER_LONG; s += 9 )
+            avail -= max_pdx >> s;
+    }
+
     /*
      * If domain 0 allocation isn't specified, reserve 1/16th of available
      * memory for things like DMA buffers. This reservation is clamped to 

[-- Attachment #3: Type: text/plain, Size: 138 bytes --]

_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xensource.com
http://lists.xensource.com/xen-devel

Re: [PATCH] x86/iommu: account for necessary allocations when calculating Dom0's initial allocation size

[Keir Fraser]

Thank Jan. I'm not really sure about putting your earlier patch into 4.0.2,
so can I put only this patch in for 4.0.2, replacing max_pdx with max_page?

 -- Keir

On 14/12/2010 09:03, "Jan Beulich" <JBeulich@novell.com> wrote:

> As of c/s 21812:e382656e4dcc, IOMMU related allocations for Dom0
> happen only after it got all of its memory allocated, and hence the
> reserve (mainly for setting up its swiotlb) may get exhausted without
> accounting for the necessary allocations up front.
> 
> While not precise, the estimate has been found to be within a couple
> of pages for the systems it got tested on.
> 
> For the calculation to be reasonably correct, this depends on the
> patch titled "x86/iommu: don't map RAM holes above 4G" sent out
> yesterday.
> 
> Signed-off-by: Jan Beulich <jbeulich@novell.com>
> 
> --- a/xen/arch/x86/domain_build.c
> +++ b/xen/arch/x86/domain_build.c
> @@ -191,6 +191,15 @@ static unsigned long __init compute_dom0
>      if ( is_pv_32on64_domain(d) )
>          avail -= opt_dom0_max_vcpus - 1;
>  
> +    /* Reserve memory for iommu_dom0_init() (rough estimate). */
> +    if ( iommu_enabled )
> +    {
> +        unsigned int s;
> +
> +        for ( s = 9; s < BITS_PER_LONG; s += 9 )
> +            avail -= max_pdx >> s;
> +    }
> +
>      /*
>       * If domain 0 allocation isn't specified, reserve 1/16th of available
>       * memory for things like DMA buffers. This reservation is clamped to
> 
> 
> 
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@lists.xensource.com
> http://lists.xensource.com/xen-devel

Re: [PATCH] x86/iommu: account for necessary allocations when calculating Dom0's initial allocation size

[Jan Beulich]

>>> On 14.12.10 at 10:28, Keir Fraser <keir@xen.org> wrote:
> Thank Jan. I'm not really sure about putting your earlier patch into 4.0.2,
> so can I put only this patch in for 4.0.2, replacing max_pdx with max_page?

Yes, that would be the correct equivalent without that other patch.

But it is clear that without the other one a system may not even
boot if the holes are large enough - but that's the case in plain
4.0.0 too, i.e. not a regression.

Jan

> On 14/12/2010 09:03, "Jan Beulich" <JBeulich@novell.com> wrote:
> 
>> As of c/s 21812:e382656e4dcc, IOMMU related allocations for Dom0
>> happen only after it got all of its memory allocated, and hence the
>> reserve (mainly for setting up its swiotlb) may get exhausted without
>> accounting for the necessary allocations up front.
>> 
>> While not precise, the estimate has been found to be within a couple
>> of pages for the systems it got tested on.
>> 
>> For the calculation to be reasonably correct, this depends on the
>> patch titled "x86/iommu: don't map RAM holes above 4G" sent out
>> yesterday.
>> 
>> Signed-off-by: Jan Beulich <jbeulich@novell.com>
>> 
>> --- a/xen/arch/x86/domain_build.c
>> +++ b/xen/arch/x86/domain_build.c
>> @@ -191,6 +191,15 @@ static unsigned long __init compute_dom0
>>      if ( is_pv_32on64_domain(d) )
>>          avail -= opt_dom0_max_vcpus - 1;
>>  
>> +    /* Reserve memory for iommu_dom0_init() (rough estimate). */
>> +    if ( iommu_enabled )
>> +    {
>> +        unsigned int s;
>> +
>> +        for ( s = 9; s < BITS_PER_LONG; s += 9 )
>> +            avail -= max_pdx >> s;
>> +    }
>> +
>>      /*
>>       * If domain 0 allocation isn't specified, reserve 1/16th of available
>>       * memory for things like DMA buffers. This reservation is clamped to
>> 
>> 
>> 
>> _______________________________________________
>> Xen-devel mailing list
>> Xen-devel@lists.xensource.com 
>> http://lists.xensource.com/xen-devel