spapr: Implement Open Firmware client interface

The PAPR platform describes an OS environment that's presented by
a combination of a hypervisor and firmware. The features it specifies
require collaboration between the firmware and the hypervisor.

Since the beginning, the runtime component of the firmware (RTAS) has
been implemented as a 20 byte shim which simply forwards it to
a hypercall implemented in qemu. The boot time firmware component is
SLOF - but a build that's specific to qemu, and has always needed to be
updated in sync with it. Even though we've managed to limit the amount
of runtime communication we need between qemu and SLOF, there's some,
and it has become increasingly awkward to handle as we've implemented
new features.

This implements a boot time OF client interface (CI) which is
enabled by a new "x-vof" pseries machine option (stands for "Virtual Open
Firmware). When enabled, QEMU implements the custom H_OF_CLIENT hcall
which implements Open Firmware Client Interface (OF CI). This allows
using a smaller stateless firmware which does not have to manage
the device tree.

The new "vof.bin" firmware image is included with source code under
pc-bios/. It also includes RTAS blob.

This implements a handful of CI methods just to get -kernel/-initrd
working. In particular, this implements the device tree fetching and
simple memory allocator - "claim" (an OF CI memory allocator) and updates
"/memory@0/available" to report the client about available memory.

This implements changing some device tree properties which we know how
to deal with, the rest is ignored. To allow changes, this skips
fdt_pack() when x-vof=on as not packing the blob leaves some room for
appending.

In absence of SLOF, this assigns phandles to device tree nodes to make
device tree traversing work.

When x-vof=on, this adds "/chosen" every time QEMU (re)builds a tree.

This adds basic instances support which are managed by a hash map
ihandle -> [phandle].

Before the guest started, the used memory is:
0..e60 - the initial firmware
8000..10000 - stack
400000.. - kernel
3ea0000.. - initramdisk

This OF CI does not implement "interpret".

Unlike SLOF, this does not format uninitialized nvram. Instead, this
includes a disk image with pre-formatted nvram.

With this basic support, this can only boot into kernel directly.
However this is just enough for the petitboot kernel and initradmdisk to
boot from any possible source. Note this requires reasonably recent guest
kernel with:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=df5be5be8735

The immediate benefit is much faster booting time which especially
crucial with fully emulated early CPU bring up environments. Also this
may come handy when/if GRUB-in-the-userspace sees light of the day.

This separates VOF and sPAPR in a hope that VOF bits may be reused by
other POWERPC boards which do not support pSeries.

This assumes potential support for booting from QEMU backends
such as blockdev or netdev without devices/drivers used.

Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Message-Id: <20210625055155.2252896-1-aik@ozlabs.ru>
Reviewed-by: BALATON Zoltan <balaton@eik.bme.hu>
[dwg: Adjusted some includes which broke compile in some more obscure
 compilation setups]
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

1 files changed, 60 insertions, 7 deletions

diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
index 9e19c57032..e9b6d0f587 100644
--- a/hw/ppc/spapr.c
+++ b/hw/ppc/spapr.c
@@ -101,6 +101,7 @@
 #define FDT_MAX_ADDR            0x80000000 /* FDT must stay below that */
 #define FW_MAX_SIZE             0x400000
 #define FW_FILE_NAME            "slof.bin"
+#define FW_FILE_NAME_VOF        "vof.bin"
 #define FW_OVERHEAD             0x2800000
 #define KERNEL_LOAD_ADDR        FW_MAX_SIZE
 
@@ -1643,22 +1644,37 @@ static void spapr_machine_reset(MachineState *machine)
     fdt_addr = MIN(spapr->rma_size, FDT_MAX_ADDR) - FDT_MAX_SIZE;
 
     fdt = spapr_build_fdt(spapr, true, FDT_MAX_SIZE);
+    if (spapr->vof) {
+        target_ulong stack_ptr = 0;
 
-    rc = fdt_pack(fdt);
+        spapr_vof_reset(spapr, fdt, &stack_ptr, &error_fatal);
 
-    /* Should only fail if we've built a corrupted tree */
-    assert(rc == 0);
+        spapr_cpu_set_entry_state(first_ppc_cpu, SPAPR_ENTRY_POINT,
+                                  stack_ptr, spapr->initrd_base,
+                                  spapr->initrd_size);
+        /* VOF is 32bit BE so enforce MSR here */
+        first_ppc_cpu->env.msr &= ~((1ULL << MSR_SF) | (1ULL << MSR_LE));
+        /*
+         * Do not pack the FDT as the client may change properties.
+         * VOF client does not expect the FDT so we do not load it to the VM.
+         */
+    } else {
+        rc = fdt_pack(fdt);
+        /* Should only fail if we've built a corrupted tree */
+        assert(rc == 0);
 
-    /* Load the fdt */
+        spapr_cpu_set_entry_state(first_ppc_cpu, SPAPR_ENTRY_POINT,
+                                  0, fdt_addr, 0);
+        cpu_physical_memory_write(fdt_addr, fdt, fdt_totalsize(fdt));
+    }
     qemu_fdt_dumpdtb(fdt, fdt_totalsize(fdt));
-    cpu_physical_memory_write(fdt_addr, fdt, fdt_totalsize(fdt));
+
     g_free(spapr->fdt_blob);
     spapr->fdt_size = fdt_totalsize(fdt);
     spapr->fdt_initial_size = spapr->fdt_size;
     spapr->fdt_blob = fdt;
 
     /* Set up the entry state */
-    spapr_cpu_set_entry_state(first_ppc_cpu, SPAPR_ENTRY_POINT, 0, fdt_addr, 0);
     first_ppc_cpu->env.gpr[5] = 0;
 
     spapr->fwnmi_system_reset_addr = -1;
@@ -2661,7 +2677,8 @@ static void spapr_machine_init(MachineState *machine)
     SpaprMachineState *spapr = SPAPR_MACHINE(machine);
     SpaprMachineClass *smc = SPAPR_MACHINE_GET_CLASS(machine);
     MachineClass *mc = MACHINE_GET_CLASS(machine);
-    const char *bios_name = machine->firmware ?: FW_FILE_NAME;
+    const char *bios_default = spapr->vof ? FW_FILE_NAME_VOF : FW_FILE_NAME;
+    const char *bios_name = machine->firmware ?: bios_default;
     const char *kernel_filename = machine->kernel_filename;
     const char *initrd_filename = machine->initrd_filename;
     PCIHostState *phb;
@@ -3018,6 +3035,10 @@ static void spapr_machine_init(MachineState *machine)
     }
 
     qemu_cond_init(&spapr->fwnmi_machine_check_interlock_cond);
+    if (spapr->vof) {
+        spapr->vof->fw_size = fw_size; /* for claim() on itself */
+        spapr_register_hypercall(KVMPPC_H_VOF_CLIENT, spapr_h_vof_client);
+    }
 }
 
 #define DEFAULT_KVM_TYPE "auto"
@@ -3208,6 +3229,28 @@ static void spapr_set_resize_hpt(Object *obj, const char *value, Error **errp)
     }
 }
 
+static bool spapr_get_vof(Object *obj, Error **errp)
+{
+    SpaprMachineState *spapr = SPAPR_MACHINE(obj);
+
+    return spapr->vof != NULL;
+}
+
+static void spapr_set_vof(Object *obj, bool value, Error **errp)
+{
+    SpaprMachineState *spapr = SPAPR_MACHINE(obj);
+
+    if (spapr->vof) {
+        vof_cleanup(spapr->vof);
+        g_free(spapr->vof);
+        spapr->vof = NULL;
+    }
+    if (!value) {
+        return;
+    }
+    spapr->vof = g_malloc0(sizeof(*spapr->vof));
+}
+
 static char *spapr_get_ic_mode(Object *obj, Error **errp)
 {
     SpaprMachineState *spapr = SPAPR_MACHINE(obj);
@@ -3333,6 +3376,11 @@ static void spapr_instance_init(Object *obj)
                                     stringify(KERNEL_LOAD_ADDR)
                                     " for -kernel is the default");
     spapr->kernel_addr = KERNEL_LOAD_ADDR;
+
+    object_property_add_bool(obj, "x-vof", spapr_get_vof, spapr_set_vof);
+    object_property_set_description(obj, "x-vof",
+                                    "Enable Virtual Open Firmware (experimental)");
+
     /* The machine class defines the default interrupt controller mode */
     spapr->irq = smc->irq;
     object_property_add_str(obj, "ic-mode", spapr_get_ic_mode,
@@ -4496,6 +4544,7 @@ static void spapr_machine_class_init(ObjectClass *oc, void *data)
     XICSFabricClass *xic = XICS_FABRIC_CLASS(oc);
     InterruptStatsProviderClass *ispc = INTERRUPT_STATS_PROVIDER_CLASS(oc);
     XiveFabricClass *xfc = XIVE_FABRIC_CLASS(oc);
+    VofMachineIfClass *vmc = VOF_MACHINE_CLASS(oc);
 
     mc->desc = "pSeries Logical Partition (PAPR compliant)";
     mc->ignore_boot_device_suffixes = true;
@@ -4584,6 +4633,9 @@ static void spapr_machine_class_init(ObjectClass *oc, void *data)
     smc->smp_threads_vsmt = true;
     smc->nr_xirqs = SPAPR_NR_XIRQS;
     xfc->match_nvt = spapr_match_nvt;
+    vmc->client_architecture_support = spapr_vof_client_architecture_support;
+    vmc->quiesce = spapr_vof_quiesce;
+    vmc->setprop = spapr_vof_setprop;
 }
 
 static const TypeInfo spapr_machine_info = {
@@ -4603,6 +4655,7 @@ static const TypeInfo spapr_machine_info = {
         { TYPE_XICS_FABRIC },
         { TYPE_INTERRUPT_STATS_PROVIDER },
         { TYPE_XIVE_FABRIC },
+        { TYPE_VOF_MACHINE_IF },
         { }
     },
 };