Re: [Xen-devel] Design doc of adding ACPI support for arm64 on Xen - version 2

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Fri, 7 Aug 2015, Shannon Zhao wrote:
> This document is going to explain the design details of Xen booting with
> ACPI on ARM. Maybe parts of it may not be appropriate. Any comments are
> welcome.
> 
> To Xen itself booting with ACPI, this is similar to Linux kernel except
> that Xen doesn't parse DSDT table. So I'll skip this part and focus on
> how Xen prepares ACPI tables for Dom0 and how Xen passes them to Dom0.
> 
> 1. Copy and change some EFI and ACPI tables
> -------------------------------------------
> a) Copy EFI_SYSTEM_TABLE and change the value of FirmwareVendor,
> VendorGuid, VendorTable, ConfigurationTable. These changes are not very
> special and it just assign values to these members.
> 
> b) Create EFI_MEMORY_DESCRIPTOR table. This will add memory start and
> size information of Dom0. And Dom0 will get the memory information
> through this EFI table.
> 
> c) Copy FADT table. Change the value of arm_boot_flags to enable PSCI
> and HVC. Let the hypervisor_id be "XenVMM" in order to tell Dom0 that it
> runs on Xen hypervisor, then Dom0 could through HVM_PARAM to get some
> informations for booting necessity, such as grant table start address
> and size. Change header revison, length and checksum as well.
> 
> d) Copy GTDT table. Set non_secure_el2_interrupt and
> non_secure_el2_flags to 0 to mask EL2 timer for Dom0.
> 
> e) Copy MADT table. According to the value of dom0_max_vcpus to change
> the number GICC entries.
> 
> f) Create STAO table. This table is a new added one that's used to
> define a list of ACPI namespace names that are to be ignored by the OSPM
> in Dom0. Currently we use it to tell OSPM should ignore UART defined in
> SPCR table.
> 
> g) Copy XSDT table. Add a new table entry for STAO and change other
> table's entries.
> 
> h) Change the value of xsdt_physical_address in RSDP table.
> 
> i) The rest of tables are not copied or changed. They are reused
> including DSDT, SPCR, etc.
> 
> All these tables will be copied to Dom0 memory except that the reused
> tables(DSDT, SPCR, etc) will be mapped to Dom0.
> 
> 2. Create minimal DT to pass required information to Dom0
> ----------------------------------------------------------
> The minimal DT mainly passes Dom0 bootargs, address and size of initrd
> (if available), address and size of uefi system table, address and size
> of uefi memory table, uefi-mmap-desc-size and uefi-mmap-desc-ver.
> 
> An example of the minimal DT:
> / {
>     #address-cells = <2>;
>     #size-cells = <1>;
>     chosen {
>         bootargs = "kernel=Image console=hvc0 earlycon=pl011,0x1c090000
> root=/dev/vda2 rw rootfstype=ext4 init=/bin/sh acpi=force";
>         linux,initrd-start = <0xXXXXXXXX>;
>         linux,initrd-end = <0xXXXXXXXX>;
>         linux,uefi-system-table = <0xXXXXXXXX>;
>         linux,uefi-mmap-start = <0xXXXXXXXX>;
>         linux,uefi-mmap-size = <0xXXXXXXXX>;
>         linux,uefi-mmap-desc-size = <0xXXXXXXXX>;
>         linux,uefi-mmap-desc-ver = <0xXXXXXXXX>;
>     };
> };
> 
> For details loook at
> https://github.com/torvalds/linux/blob/master/Documentation/arm/uefi.txt
> 
> 3. Dom0 gets grant table and event channel irq information
> -----------------------------------------------------------
> As said above, we assign the hypervisor_id be "XenVMM" to tell Dom0 that
> it runs on Xen hypervisor.
> 
> For grant table, add two new HVM_PARAMs: HVM_PARAM_GNTTAB_START_ADDRESS
> and HVM_PARAM_GNTTAB_SIZE.
> 
> For event channel irq, reuse HVM_PARAM_CALLBACK_IRQ and add a new
> delivery type:
> val[63:56] == 3: val[15:8] is flag: val[7:0] is a PPI (ARM and ARM64
> only)
> 
> When constructing Dom0 in Xen, save these values. Then Dom0 could get
> them through hypercall HVMOP_get_param.
> 
> 4. Map MMIO regions
> -------------------
> Register a bus_notifier for platform and amba bus in Linux. Add a new
> XENMAPSPACE "XENMAPSPACE_dev_mmio". Within the register, check if the
> device is newly added, then call hypercall XENMEM_add_to_physmap to map
> the mmio regions.
> 
> 5. Route device interrupts to Dom0
> ----------------------------------
> Route all the SPI interrupts to Dom0 before Dom0 booting.
> 
> 
> Look forward to your comments. If you think it has no problem, giving
> your ack would be a big help. Then the patchset could move on. :)

Indeed.

Acked-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>

It would be nice to have an Ack from Jan too. He should be back in a
couple of days.

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