Re: [PATCH 5/6] hw/ppc: Pass device tree properties for Fadump

[Harsh Prateek Bora]

On 2/27/25 08:58, Nicholas Piggin wrote:
On Mon Feb 17, 2025 at 5:17 PM AEST, Aditya Gupta wrote:
Platform (ie. QEMU) is expected to pass few device tree properties for
details for fadump:

   * "ibm,configure-kernel-dump": RTAS call for fadump
   * "ibm,configure-kernel-dump-sizes": Space required to store dump data
     for firmware provided dump sections (ie. CPU & HPTE regions)
   * "ibm,configure-kernel-dump-version": Versions of fadump supported
   * "ibm,kernel-dump": Contains the Fadump Memory Structure on a fadump
     boot

Implement passing configure-kernel-dump-sizes, and
configure-kernel-dump-version device tree properties, irrespective of
whether it's a fadump boot or not, so that kernel can reserve memory to
store the firmware provided dump sections in case of a crash

Also, in case of a fadump boot, pass the fadump memory structure to the
kernel in "ibm,kernel-dump" device tree property.

Signed-off-by: Aditya Gupta <adit...@linux.ibm.com>
---
  hw/ppc/spapr.c         | 62 ++++++++++++++++++++++++++++++++++++++++++
  include/hw/ppc/spapr.h |  2 ++
  2 files changed, 64 insertions(+)

diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
index f3a4b4235d43..3602e5b5d18d 100644
--- a/hw/ppc/spapr.c
+++ b/hw/ppc/spapr.c
@@ -897,9 +897,27 @@ static int spapr_dt_rng(void *fdt)
  static void spapr_dt_rtas(SpaprMachineState *spapr, void *fdt)
  {

You might be able to add a spapr_dt_rtas_fadump() function
and do it there to help keep functions small?

Ditto. Would look nicer coming from spapr_fadump.[ch] as suggested by 
Nick earlier.

Thanks
Harsh

Thanks,
Nick

      MachineState *ms = MACHINE(spapr);
+    MachineClass *mc = MACHINE_GET_CLASS(ms);
      int rtas;
      GString *hypertas = g_string_sized_new(256);
      GString *qemu_hypertas = g_string_sized_new(256);
+    uint32_t max_possible_cpus = mc->possible_cpu_arch_ids(ms)->len;
+    uint64_t fadump_cpu_state_size = 0;
+    uint16_t fadump_versions[2] = {
+        FADUMP_VERSION /* min supported version */,
+        FADUMP_VERSION /* max supported version */
+    };
+    uint32_t fadump_rgn_sizes[2][3] = {
+        {
+            cpu_to_be32(FADUMP_CPU_STATE_DATA),
+            0, 0 /* Calculated later */
+        },
+        {
+            cpu_to_be32(FADUMP_HPTE_REGION),
+            0, 0 /* HPTE region not implemented */
+        }
+    };
+
      uint32_t lrdr_capacity[] = {
          0,
          0,
@@ -1006,6 +1024,50 @@ static void spapr_dt_rtas(SpaprMachineState *spapr, void 
*fdt)
      _FDT(fdt_setprop(fdt, rtas, "ibm,lrdr-capacity",
                       lrdr_capacity, sizeof(lrdr_capacity)));
  
+    /*
+     * CPU State Data contains multiple fields such as header, num_cpus and
+     * register entries
+     *
+     * Calculate the maximum CPU State Data size, according to maximum
+     * possible CPUs the QEMU VM can have
+     */
+    /* Reg save header */
+    fadump_cpu_state_size += sizeof(struct rtas_fadump_reg_save_area_header);
+
+    /* Num_cpus */
+    fadump_cpu_state_size += sizeof(__be32);
+
+    /* Register Entries */
+    fadump_cpu_state_size += max_possible_cpus   *
+                             FADUMP_NUM_PER_CPU_REGS *
+                             sizeof(struct rtas_fadump_reg_entry);
+
+    /* Set maximum size for CPU state data region */
+    assert(fadump_rgn_sizes[0][0] == cpu_to_be32(FADUMP_CPU_STATE_DATA));
+
+    /* Upper 32 bits of size, usually 0 */
+    fadump_rgn_sizes[0][1] = cpu_to_be32(fadump_cpu_state_size >> 32);
+
+    /* Lower 32 bits of size */
+    fadump_rgn_sizes[0][2] = cpu_to_be32(fadump_cpu_state_size & 0xffffffff);
+
+    /* Add device tree properties required from platform for fadump */
+    _FDT((fdt_setprop(fdt, rtas, "ibm,configure-kernel-dump-version",
+                    fadump_versions, sizeof(fadump_versions))));
+    _FDT((fdt_setprop(fdt, rtas, "ibm,configure-kernel-dump-sizes",
+                    fadump_rgn_sizes, sizeof(fadump_rgn_sizes))));
+
+    if (is_next_boot_fadump) {
+        struct rtas_fadump_mem_struct *fdm =
+            &fadump_metadata.registered_fdm;
+
+        uint64_t fdm_size =
+            sizeof(struct rtas_fadump_section_header) +
+            (be16_to_cpu(fdm->header.dump_num_sections) *
+            sizeof(struct rtas_fadump_section));
+
+        _FDT((fdt_setprop(fdt, rtas, "ibm,kernel-dump", fdm, fdm_size)));
+    }
      spapr_dt_rtas_tokens(fdt, rtas);
  }
  
diff --git a/include/hw/ppc/spapr.h b/include/hw/ppc/spapr.h
index 0e8002bad9e0..fa63008e57ec 100644
--- a/include/hw/ppc/spapr.h
+++ b/include/hw/ppc/spapr.h
@@ -928,6 +928,8 @@ static inline uint64_t fadump_gpr_id_to_u64(uint32_t gpr_id)
      return val;
  }
  
+extern bool is_next_boot_fadump;
+
  struct fadump_metadata {
      bool fadump_registered;
      bool fadump_dump_active;