On 31/03/2021 13:53, Alexey Kardashevskiy wrote:
The PAPR platform which 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 is coded in assumption that later on we might be adding support for
booting from QEMU backends (blockdev is the first candidate) without
devices/drivers in between as OF1275 does not require that and
it is quite easy to so.
Signed-off-by: Alexey Kardashevskiy <a...@ozlabs.ru>
[...]
diff --git a/hw/ppc/spapr_vof.c b/hw/ppc/spapr_vof.c
new file mode 100644
index 000000000000..9d22e230e3c0
--- /dev/null
+++ b/hw/ppc/spapr_vof.c
[...]
+
+void spapr_vof_client_dt_finalize(SpaprMachineState *spapr, void *fdt)
+{
+ char *stdout_path = spapr_vio_stdout_path(spapr->vio_bus);
+
+ vof_build_dt(fdt, spapr->vof);
+
+ /*
+ * SLOF-less setup requires an open instance of stdout for early
+ * kernel printk. By now all phandles are settled so we can open
+ * the default serial console.
+ */
+ if (stdout_path) {
+ _FDT(vof_client_open_store(fdt, spapr->vof, "/chosen", "stdout",
+ stdout_path));
+ }
+}
+
+void spapr_vof_reset(SpaprMachineState *spapr, void *fdt,
+ target_ulong *stack_ptr, Error **errp)
+{
+ Vof *vof = spapr->vof;
+
+ vof_init(vof, spapr->rma_size);
+
+ if (vof_claim(vof, 0, spapr->fw_size, 0) == -1) {
+ error_setg(errp, "Memory for firmware is in use");
+ return;
+ }
+
+ *stack_ptr = vof_claim(vof, 0, OF_STACK_SIZE, OF_STACK_SIZE);
+ if (*stack_ptr == -1) {
+ error_setg(errp, "Memory allocation for stack failed");
+ return;
+ }
+ /* Stack grows downwards plus reserve space for the minimum stack frame */
+ *stack_ptr += OF_STACK_SIZE - 0x20;
+
+ if (spapr->kernel_size &&
+ vof_claim(vof, spapr->kernel_addr, spapr->kernel_size, 0) == -1) {
+ error_setg(errp, "Memory for kernel is in use");
+ return;
+ }
+
+ if (spapr->initrd_size &&
+ vof_claim(vof, spapr->initrd_base, spapr->initrd_size, 0) == -1) {
+ error_setg(errp, "Memory for initramdisk is in use");
+ return;
+ }
+
+ spapr_vof_client_dt_finalize(spapr, fdt);
+
+ /*
+ * We skip writing FDT as nothing expects it; OF client interface is
+ * going to be used for reading the device tree.
+ */
+}
This is missing "bootargs" from below.
diff --git a/hw/ppc/vof.c b/hw/ppc/vof.c
new file mode 100644
index 000000000000..57d140b6ff33
--- /dev/null
+++ b/hw/ppc/vof.c
[...]
+static uint32_t vof_setprop(void *fdt, Vof *vof,
+ uint32_t nodeph, uint32_t pname,
+ uint32_t valaddr, uint32_t vallen)
+{
+ char propname[OF_PROPNAME_LEN_MAX + 1];
+ uint32_t ret = -1;
+ int offset;
+ char trval[64] = "";
+ char nodepath[VOF_MAX_PATH] = "";
+ g_autofree char *data = NULL;
+
+ if (vallen > VOF_MAX_PROPLEN) {
+ goto trace_exit;
+ }
+ if (readstr(pname, propname, sizeof(propname))) {
+ goto trace_exit;
+ }
+ offset = fdt_node_offset_by_phandle(fdt, nodeph);
+ if (offset < 0) {
+ goto trace_exit;
+ }
+ ret = get_path(fdt, offset, nodepath, sizeof(nodepath));
+ if (ret <= 0) {
+ goto trace_exit;
+ }
+
+ ret = -1;
+ /*
+ * We only allow changing properties which we know how to update in QEMU
+ * OR
+ * the ones which we know that they need to survive during "quiesce".
+ */
+ if (strcmp(nodepath, "/rtas") == 0) {
+ if (strcmp(propname, "linux,rtas-base") == 0 ||
+ strcmp(propname, "linux,rtas-entry") == 0) {
+ /* These need to survive quiesce so let them store in the FDT */
+ } else {
+ goto trace_exit;
+ }
+ } else if (strcmp(nodepath, "/chosen") == 0) {
+ if (strcmp(propname, "bootargs") == 0) {
+ char val[1024];
+
+ if (readstr(valaddr, val, sizeof(val))) {
+ goto trace_exit;
+ }
+ g_free(vof->bootargs);
+ vof->bootargs = g_strdup(val);
+ vallen = strlen(vof->bootargs) + 1;
... ^^^ this one. Otherwise "-append" is lost after "quiescence", or
bootargs from grub.conf (if the blockdev patch applied).
So, David, if you feel ok to put this in ppc-for-6.1, then let me know,
I'll repost with whatever fixes I may have by then. Thanks,
--
Alexey
