Merge tag 'mem-2023-09-19' of https://github.com/davidhildenbrand/qemu into staging

Hi,

"Host Memory Backends" and "Memory devices" queue ("mem"):
- Support and document VM templating with R/O files using a new "rom"
  parameter for memory-backend-file
- Some cleanups and fixes around NVDIMMs and R/O file handling for guest
  RAM
- Optimize ioeventfd updates by skipping address spaces that are not
  applicable

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# gpg: Signature made Tue 19 Sep 2023 06:25:45 EDT
# gpg:                using RSA key 1BD9CAAD735C4C3A460DFCCA4DDE10F700FF835A
# gpg:                issuer "david@redhat.com"
# gpg: Good signature from "David Hildenbrand <david@redhat.com>" [unknown]
# gpg:                 aka "David Hildenbrand <davidhildenbrand@gmail.com>" [full]
# gpg:                 aka "David Hildenbrand <hildenbr@in.tum.de>" [unknown]
# gpg: WARNING: The key's User ID is not certified with a trusted signature!
# gpg:          There is no indication that the signature belongs to the owner.
# Primary key fingerprint: 1BD9 CAAD 735C 4C3A 460D  FCCA 4DDE 10F7 00FF 835A

* tag 'mem-2023-09-19' of https://github.com/davidhildenbrand/qemu:
  memory: avoid updating ioeventfds for some address_space
  machine: Improve error message when using default RAM backend id
  softmmu/physmem: Hint that "readonly=on,rom=off" exists when opening file R/W for private mapping fails
  docs: Start documenting VM templating
  docs: Don't mention "-mem-path" in multi-process.rst
  softmmu/physmem: Never return directories from file_ram_open()
  softmmu/physmem: Fail creation of new files in file_ram_open() with readonly=true
  softmmu/physmem: Bail out early in ram_block_discard_range() with readonly files
  softmmu/physmem: Remap with proper protection in qemu_ram_remap()
  backends/hostmem-file: Add "rom" property to support VM templating with R/O files
  softmmu/physmem: Distinguish between file access mode and mmap protection
  nvdimm: Reject writing label data to ROM instead of crashing QEMU

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

4 files changed, 25 insertions, 10 deletions

diff --git a/hw/acpi/nvdimm.c b/hw/acpi/nvdimm.c
index a3b25a9..3cbd416 100644
--- a/hw/acpi/nvdimm.c
+++ b/hw/acpi/nvdimm.c
@@ -670,7 +670,8 @@ static void nvdimm_dsm_label_size(NVDIMMDevice *nvdimm, hwaddr dsm_mem_addr)
 }
 
 static uint32_t nvdimm_rw_label_data_check(NVDIMMDevice *nvdimm,
-                                           uint32_t offset, uint32_t length)
+                                           uint32_t offset, uint32_t length,
+                                           bool is_write)
 {
     uint32_t ret = NVDIMM_DSM_RET_STATUS_INVALID;
 
@@ -690,6 +691,10 @@ static uint32_t nvdimm_rw_label_data_check(NVDIMMDevice *nvdimm,
         return ret;
     }
 
+    if (is_write && nvdimm->readonly) {
+        return NVDIMM_DSM_RET_STATUS_UNSUPPORT;
+    }
+
     return NVDIMM_DSM_RET_STATUS_SUCCESS;
 }
 
@@ -713,7 +718,7 @@ static void nvdimm_dsm_get_label_data(NVDIMMDevice *nvdimm, NvdimmDsmIn *in,
                                  get_label_data->length);
 
     status = nvdimm_rw_label_data_check(nvdimm, get_label_data->offset,
-                                        get_label_data->length);
+                                        get_label_data->length, false);
     if (status != NVDIMM_DSM_RET_STATUS_SUCCESS) {
         nvdimm_dsm_no_payload(status, dsm_mem_addr);
         return;
@@ -752,7 +757,7 @@ static void nvdimm_dsm_set_label_data(NVDIMMDevice *nvdimm, NvdimmDsmIn *in,
                                   set_label_data->length);
 
     status = nvdimm_rw_label_data_check(nvdimm, set_label_data->offset,
-                                        set_label_data->length);
+                                        set_label_data->length, true);
     if (status != NVDIMM_DSM_RET_STATUS_SUCCESS) {
         nvdimm_dsm_no_payload(status, dsm_mem_addr);
         return;
diff --git a/hw/core/machine.c b/hw/core/machine.c
index 230aab8..59208e6 100644
--- a/hw/core/machine.c
+++ b/hw/core/machine.c
@@ -1359,6 +1359,7 @@ out:
 
 void machine_run_board_init(MachineState *machine, const char *mem_path, Error **errp)
 {
+    ERRP_GUARD();
     MachineClass *machine_class = MACHINE_GET_CLASS(machine);
     ObjectClass *oc = object_class_by_name(machine->cpu_type);
     CPUClass *cc;
@@ -1387,9 +1388,13 @@ void machine_run_board_init(MachineState *machine, const char *mem_path, Error *
                numa_uses_legacy_mem()) {
         if (object_property_find(object_get_objects_root(),
                                  machine_class->default_ram_id)) {
-            error_setg(errp, "object name '%s' is reserved for the default"
-                " RAM backend, it can't be used for any other purposes."
-                " Change the object's 'id' to something else",
+            error_setg(errp, "object's id '%s' is reserved for the default"
+                " RAM backend, it can't be used for any other purposes",
+                machine_class->default_ram_id);
+            error_append_hint(errp,
+                "Change the object's 'id' to something else or disable"
+                " automatic creation of the default RAM backend by setting"
+                " 'memory-backend=%s' with '-machine'.\n",
                 machine_class->default_ram_id);
             return;
         }
diff --git a/hw/mem/nvdimm.c b/hw/mem/nvdimm.c
index 31080c2..1631a7d 100644
--- a/hw/mem/nvdimm.c
+++ b/hw/mem/nvdimm.c
@@ -154,6 +154,9 @@ static void nvdimm_prepare_memory_region(NVDIMMDevice *nvdimm, Error **errp)
                    object_get_canonical_path_component(OBJECT(hostmem)));
         return;
     }
+    if (memory_region_is_rom(mr)) {
+        nvdimm->readonly = true;
+    }
 
     nvdimm->nvdimm_mr = g_new(MemoryRegion, 1);
     memory_region_init_alias(nvdimm->nvdimm_mr, OBJECT(dimm),
@@ -207,15 +210,16 @@ static void nvdimm_unrealize(PCDIMMDevice *dimm)
  * label read/write functions.
  */
 static void nvdimm_validate_rw_label_data(NVDIMMDevice *nvdimm, uint64_t size,
-                                        uint64_t offset)
+                                        uint64_t offset, bool is_write)
 {
     assert((nvdimm->label_size >= size + offset) && (offset + size > offset));
+    assert(!is_write || !nvdimm->readonly);
 }
 
 static void nvdimm_read_label_data(NVDIMMDevice *nvdimm, void *buf,
                                    uint64_t size, uint64_t offset)
 {
-    nvdimm_validate_rw_label_data(nvdimm, size, offset);
+    nvdimm_validate_rw_label_data(nvdimm, size, offset, false);
 
     memcpy(buf, nvdimm->label_data + offset, size);
 }
@@ -229,7 +233,7 @@ static void nvdimm_write_label_data(NVDIMMDevice *nvdimm, const void *buf,
                                             "pmem", NULL);
     uint64_t backend_offset;
 
-    nvdimm_validate_rw_label_data(nvdimm, size, offset);
+    nvdimm_validate_rw_label_data(nvdimm, size, offset, true);
 
     if (!is_pmem) {
         memcpy(nvdimm->label_data + offset, buf, size);
diff --git a/hw/ppc/spapr_nvdimm.c b/hw/ppc/spapr_nvdimm.c
index a868824..60d6d0a 100644
--- a/hw/ppc/spapr_nvdimm.c
+++ b/hw/ppc/spapr_nvdimm.c
@@ -320,7 +320,8 @@ static target_ulong h_scm_write_metadata(PowerPCCPU *cpu,
 
     nvdimm = NVDIMM(drc->dev);
     if ((offset + len < offset) ||
-        (nvdimm->label_size < len + offset)) {
+        (nvdimm->label_size < len + offset) ||
+        nvdimm->readonly) {
         return H_P2;
     }