Re: [ImageBuilder][PATCH 2/2] uboot-script-gen: Add support for static shared memory

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Thu, 2 Mar 2023, jiamei.xie wrote:
> Introduce support for creating shared-mem node for dom0less domUs in
> the device tree. Add the following options:
> - DOMU_SHARED_MEM[number]="HPA GPA size"
>   if specified, indicates the host physical address HPA will get mapped
>   at guest address GPA in domU and the memory of size will be reserved
>   to be shared memory.
> - DOMU_SHARED_MEM_ID[number]
>   An arbitrary string that represents the unique identifier of the shared
>   memory region, with a strict limit on the number of characters(\0
>   included)
> 
> The static shared memory is used between two dom0less domUs.
> 
> Below is an example:
> NUM_DOMUS=2
> DOMU_SHARED_MEM[0]="0x50000000 0x6000000 0x10000000"
> DOMU_SHARED_MEM_ID[0]="my-shared-mem-0"
> DOMU_SHARED_MEM[1]="0x50000000 0x6000000 0x10000000"
> DOMU_SHARED_MEM_ID[1]="my-shared-mem-0"

Rather than two separate properties, do you think it would make sense to
just use one as follows?

NUM_DOMUS=2
DOMU_SHARED_MEM[0]="my-shared-mem-0 0x50000000 0x6000000 0x10000000"
DOMU_SHARED_MEM[1]="my-shared-mem-0 0x50000000 0x6000000 0x10000000"

The good thing about bash is that it doesn't care if they are numbers or
strings :-)


> This static shared memory region is identified as "my-shared-mem-0", host
> physical address starting at 0x50000000 of 256MB will be reserved to be
> shared between two domUs. It will get mapped at 0x6000000 in both guest
> physical address space. Both DomUs are the borrower domain, the owner
> domain is the default owner domain DOMID_IO.
> 
> Signed-off-by: jiamei.xie <jiamei.xie@xxxxxxx>
> ---
>  README.md                | 18 ++++++++++++++++++
>  scripts/uboot-script-gen | 26 ++++++++++++++++++++++++++
>  2 files changed, 44 insertions(+)
> 
> diff --git a/README.md b/README.md
> index 787f413..48044ee 100644
> --- a/README.md
> +++ b/README.md
> @@ -192,6 +192,24 @@ Where:
>    if specified, indicates the host physical address regions
>    [baseaddr, baseaddr + size) to be reserved to the VM for static allocation.
>  
> +- DOMU_SHARED_MEM[number]="HPA GPA size" and DOMU_SHARED_MEM_ID[number]
> +  if specified, indicate the host physical address HPA will get mapped at
> +  guest address GPA in domU and the memory of size will be reserved to be
> +  shared memory. The shared memory is used between two dom0less domUs.
> +
> +  Below is an example:
> +  NUM_DOMUS=2
> +  DOMU_SHARED_MEM[0]="0x50000000 0x6000000 0x10000000"
> +  DOMU_SHARED_MEM_ID[0]="my-shared-mem-0"
> +  DOMU_SHARED_MEM[1]="0x50000000 0x6000000 0x10000000"
> +  DOMU_SHARED_MEM_ID[1]="my-shared-mem-0"
> +
> +  This static shared memory region is identified as "my-shared-mem-0", host
> +  physical address starting at 0x50000000 of 256MB will be reserved to be
> +  shared between two domUs. It will get mapped at 0x6000000 in both guest
> +  physical address space. Both DomUs are the borrower domain, the owner
> +  domain is the default owner domain DOMID_IO.
> +
>  - DOMU_DIRECT_MAP[number] can be set to 1 or 0.
>    If set to 1, the VM is direct mapped. The default is 1.
>    This is only applicable when DOMU_STATIC_MEM is specified.
> diff --git a/scripts/uboot-script-gen b/scripts/uboot-script-gen
> index 4775293..46215c8 100755
> --- a/scripts/uboot-script-gen
> +++ b/scripts/uboot-script-gen
> @@ -204,6 +204,27 @@ function add_device_tree_static_heap()
>      dt_set "$path" "xen,static-heap" "hex" "${cells[*]}"
>  }
>  
> +function add_device_tree_static_shared_mem()
> +{
> +    local path=$1
> +    local domid=$2
> +    local regions=$3
> +    local SHARED_MEM_ID=$4
> +    local cells=()
> +    local SHARED_MEM_HOST=${regions%% *}
> +
> +    dt_mknode "${path}" "domU${domid}-shared-mem@${SHARED_MEM_HOST}"
> +
> +    for val in ${regions[@]}
> +    do
> +        cells+=("$(printf "0x%x 0x%x" $(($val >> 32)) $(($val & ((1 << 32) - 
> 1))))")
> +    done
> +
> +    dt_set "${path}/domU${domid}-shared-mem@${SHARED_MEM_HOST}" "compatible" 
> "str" "xen,domain-shared-memory-v1"
> +    dt_set "${path}/domU${domid}-shared-mem@${SHARED_MEM_HOST}" "xen,shm-id" 
> "str" "${SHARED_MEM_ID}"
> +    dt_set "${path}/domU${domid}-shared-mem@${SHARED_MEM_HOST}" 
> "xen,shared-mem" "hex" "${cells[*]}"
> +}
> +
>  function add_device_tree_cpupools()
>  {
>      local cpu
> @@ -329,6 +350,11 @@ function xen_device_tree_editing()
>              dt_set "/chosen/domU$i" "xen,enhanced" "str" "enabled"
>          fi
>  
> +        if test -n "${DOMU_SHARED_MEM[i]}" -a -n "${DOMU_SHARED_MEM_ID[i]}"
> +        then
> +                add_device_tree_static_shared_mem "/chosen/domU${i}" "${i}" 
> "${DOMU_SHARED_MEM[i]}" "${DOMU_SHARED_MEM_ID[i]}"
> +        fi
> +
>          if test "${DOMU_COLORS[$i]}"
>          then
>              local startcolor=$(echo "${DOMU_COLORS[$i]}"  | cut -d "-" -f 1)
> -- 
> 2.25.1
>