Re: [edk2-devel] regarding calling UEFI runtime services (mainly SetVariable) from linux or android OS which is running on xen+tianocore UEFI

[ritul guru <ritul.bits@gmail.com>]

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Thanks,
so as it is memory, does it mean if anything written in variable store, and
VM reboot happens then variable store will be flushed?



*Thanks & RegardsRitul Guru+91-9916513186*


On Mon, Feb 6, 2023 at 11:47 PM Andrew (EFI) Fish <afish@apple.com> wrote:

>
>
> On Feb 6, 2023, at 8:06 AM, ritul guru <ritul.bits@gmail.com> wrote:
>
> Hi,
>
> I have been using xen hypervisor and tianocore uefi BIOS on xen to boot to
> ubuntu OS on virtualized disk.
> and want to set a UEFI variable with UEFI runtime service SetVariable() to
> a value and the same wants to read from UEFI bootloader either grubx64.efi
> or botmgfw.efi,
> So, Is it possible to use runtime services to do such an operation for OS
> running on VM when booted with OVMF/tianocore BIOS on VM guest?
> If so, where does this variable gets stored? is it in some virtualized
> disk as there is no virtualized SPIROM available to VM.
>
>
>
> I don’t know the Xen specifics, but the firmware maps in a Flash Device
> (FD) here:
>
> [image: edk2.png]
>
> edk2/OvmfXen.fdf at master · tianocore/edk2
> <https://github.com/tianocore/edk2/blob/master/OvmfPkg/OvmfXen.fdf>
> github.com
> <https://github.com/tianocore/edk2/blob/master/OvmfPkg/OvmfXen.fdf>
> <https://github.com/tianocore/edk2/blob/master/OvmfPkg/OvmfXen.fdf>
>
> Oh looks like it uses an emulated variable store that is just memory. See
> ReserveEmuVariableNvStore().
>
> [image: edk2.png]
>
> edk2/Platform.c at master · tianocore/edk2
> <https://github.com/tianocore/edk2/blob/master/OvmfPkg/XenPlatformPei/Platform.c#L365>
> github.com
> <https://github.com/tianocore/edk2/blob/master/OvmfPkg/XenPlatformPei/Platform.c#L365>
>
> <https://github.com/tianocore/edk2/blob/master/OvmfPkg/XenPlatformPei/Platform.c#L365>
>
> Thanks,
>
> Andrew Fish
>
>
> https://wiki.osdev.org/Using_UEFI_Runtime_Services_in_your_Kernel
>
>
>
> *Thanks & RegardsRitul Guru+91-9916513186*
> 
>
>
>

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