uboot-script-gen: Add support for specifying domain P2M pool size

[ImageBuilder][PATCH] uboot-script-gen: Add support for specifying domain P2M pool size

Posted by Oleksandr Tyshchenko 5 days, 11 hours ago

The DOMU_P2M_MEM_MB configuration option is used to specify
the amount of megabytes of RAM used for the domain P2M pool.
It allows users to manually define the memory size reserved for
P2M structures in non-hardware domains, overriding the default
value calculated by Xen.

Signed-off-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
---
 README.md                | 7 +++++++
 scripts/uboot-script-gen | 5 +++++
 2 files changed, 12 insertions(+)

diff --git a/README.md b/README.md
index 983cbbc..c7ae98e 100644
--- a/README.md
+++ b/README.md
@@ -203,6 +203,13 @@ Where:
   NOTE that with this option, user needs to manually set xen,passthrough
   in xen.dtb.
 
+- DOMU_P2M_MEM_MB[number] is optional 32-bit integer specifying the amount
+  of megabytes of RAM used for the domain P2M pool. If not set, the default
+  size is calculated by Xen.
+  Note that the P2M pool is used to allocate pages for P2M structures for
+  non-hardware domains. For the hardware domain, P2M pages are allocated
+  directly from the heap.
+
 - DOMU_MEM[number] is the amount of memory for the VM in MB, default 512MB
 
 - DOMU_VCPUS[number] is the number of vcpus for the VM, default 1
diff --git a/scripts/uboot-script-gen b/scripts/uboot-script-gen
index d18ac55..0c86c2d 100755
--- a/scripts/uboot-script-gen
+++ b/scripts/uboot-script-gen
@@ -514,6 +514,11 @@ function xen_device_tree_editing()
             dt_set "/chosen/domU$i" "passthrough" "str" "enabled"
         fi
 
+        if test -n "${DOMU_P2M_MEM_MB[$i]}"
+        then
+            dt_set "/chosen/domU$i" "xen,domain-p2m-mem-mb" "int" "${DOMU_P2M_MEM_MB[$i]}"
+        fi
+
         if test -n "${DOMU_SHARED_MEM[i]}"
         then
             add_device_tree_static_shared_mem "/chosen/domU${i}" "${DOMU_SHARED_MEM[i]}"
-- 
2.34.1

Re: [ImageBuilder][PATCH] uboot-script-gen: Add support for specifying domain P2M pool size

Posted by Halder, Ayan Kumar 5 days, 11 hours ago

Hi Oleksandr,

On 20/01/2026 18:23, Oleksandr Tyshchenko wrote:
> The DOMU_P2M_MEM_MB configuration option is used to specify
> the amount of megabytes of RAM used for the domain P2M pool.
> It allows users to manually define the memory size reserved for
> P2M structures in non-hardware domains, overriding the default
> value calculated by Xen.
>
> Signed-off-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>

Reviewed-by: Ayan Kumar Halder <ayan.kumar.halder@amd.com>

with a question

> ---
>   README.md                | 7 +++++++
>   scripts/uboot-script-gen | 5 +++++
>   2 files changed, 12 insertions(+)
>
> diff --git a/README.md b/README.md
> index 983cbbc..c7ae98e 100644
> --- a/README.md
> +++ b/README.md
> @@ -203,6 +203,13 @@ Where:
>     NOTE that with this option, user needs to manually set xen,passthrough
>     in xen.dtb.
>   
> +- DOMU_P2M_MEM_MB[number] is optional 32-bit integer specifying the amount
> +  of megabytes of RAM used for the domain P2M pool. If not set, the default
> +  size is calculated by Xen.
> +  Note that the P2M pool is used to allocate pages for P2M structures for
> +  non-hardware domains. For the hardware domain, P2M pages are allocated
> +  directly from the heap.
> +
>   - DOMU_MEM[number] is the amount of memory for the VM in MB, default 512MB
>   
>   - DOMU_VCPUS[number] is the number of vcpus for the VM, default 1
> diff --git a/scripts/uboot-script-gen b/scripts/uboot-script-gen
> index d18ac55..0c86c2d 100755
> --- a/scripts/uboot-script-gen
> +++ b/scripts/uboot-script-gen
> @@ -514,6 +514,11 @@ function xen_device_tree_editing()
>               dt_set "/chosen/domU$i" "passthrough" "str" "enabled"
>           fi
>   
> +        if test -n "${DOMU_P2M_MEM_MB[$i]}"
> +        then
> +            dt_set "/chosen/domU$i" "xen,domain-p2m-mem-mb"

Was this property recently introduced in Xen ? If so, it may be good to 
refer Xen's commit id.

- Ayan

Re: [ImageBuilder][PATCH] uboot-script-gen: Add support for specifying domain P2M pool size

Posted by Oleksandr Tyshchenko 4 days, 19 hours ago


On 20.01.26 20:39, Halder, Ayan Kumar wrote:
> Hi Oleksandr,

Hello Ayan

> 
> On 20/01/2026 18:23, Oleksandr Tyshchenko wrote:
>> The DOMU_P2M_MEM_MB configuration option is used to specify
>> the amount of megabytes of RAM used for the domain P2M pool.
>> It allows users to manually define the memory size reserved for
>> P2M structures in non-hardware domains, overriding the default
>> value calculated by Xen.
>>
>> Signed-off-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
> 
> Reviewed-by: Ayan Kumar Halder <ayan.kumar.halder@amd.com>

thanks


> 
> with a question
> 
>> ---
>>   README.md                | 7 +++++++
>>   scripts/uboot-script-gen | 5 +++++
>>   2 files changed, 12 insertions(+)
>>
>> diff --git a/README.md b/README.md
>> index 983cbbc..c7ae98e 100644
>> --- a/README.md
>> +++ b/README.md
>> @@ -203,6 +203,13 @@ Where:
>>     NOTE that with this option, user needs to manually set 
>> xen,passthrough
>>     in xen.dtb.
>> +- DOMU_P2M_MEM_MB[number] is optional 32-bit integer specifying the 
>> amount
>> +  of megabytes of RAM used for the domain P2M pool. If not set, the 
>> default
>> +  size is calculated by Xen.
>> +  Note that the P2M pool is used to allocate pages for P2M structures 
>> for
>> +  non-hardware domains. For the hardware domain, P2M pages are allocated
>> +  directly from the heap.
>> +
>>   - DOMU_MEM[number] is the amount of memory for the VM in MB, default 
>> 512MB
>>   - DOMU_VCPUS[number] is the number of vcpus for the VM, default 1
>> diff --git a/scripts/uboot-script-gen b/scripts/uboot-script-gen
>> index d18ac55..0c86c2d 100755
>> --- a/scripts/uboot-script-gen
>> +++ b/scripts/uboot-script-gen
>> @@ -514,6 +514,11 @@ function xen_device_tree_editing()
>>               dt_set "/chosen/domU$i" "passthrough" "str" "enabled"
>>           fi
>> +        if test -n "${DOMU_P2M_MEM_MB[$i]}"
>> +        then
>> +            dt_set "/chosen/domU$i" "xen,domain-p2m-mem-mb"
> 
> Was this property recently introduced in Xen ?

No. It was introduced more than 3 years ago by the following commit 
cbea5a1149ca7fd4b7cdbfa3ec2e4f109b601ff7 “xen/arm: Allocate and free P2M 
pages from the P2M pool”.


  If so, it may be good to
> refer Xen's commit id.
> 
> - Ayan
>