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Re: [PATCH qemu v20] spapr: Implement Open Firmware client interface


From: BALATON Zoltan
Subject: Re: [PATCH qemu v20] spapr: Implement Open Firmware client interface
Date: Sun, 30 May 2021 19:33:01 +0200 (CEST)

Hello,

Two more problems I've found while testing with pegasos2 but I'm not sure how to fix them:

On Thu, 20 May 2021, Alexey Kardashevskiy wrote:
diff --git a/hw/ppc/vof.c b/hw/ppc/vof.c
new file mode 100644
index 000000000000..a283b7d251a7
--- /dev/null
+++ b/hw/ppc/vof.c
@@ -0,0 +1,1021 @@
+/*
+ * QEMU PowerPC Virtual Open Firmware.
+ *
+ * This implements client interface from OpenFirmware IEEE1275 on the QEMU
+ * side to leave only a very basic firmware in the VM.
+ *
+ * Copyright (c) 2021 IBM Corporation.
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ */
+
+#include "qemu/osdep.h"
+#include "qemu-common.h"
+#include "qemu/timer.h"
+#include "qemu/range.h"
+#include "qemu/units.h"
+#include "qapi/error.h"
+#include <sys/ioctl.h>
+#include "exec/ram_addr.h"
+#include "exec/address-spaces.h"
+#include "hw/ppc/vof.h"
+#include "hw/ppc/fdt.h"
+#include "sysemu/runstate.h"
+#include "qom/qom-qobject.h"
+#include "trace.h"
+
+#include <libfdt.h>
+
+/*
+ * OF 1275 "nextprop" description suggests is it 32 bytes max but
+ * LoPAPR defines "ibm,query-interrupt-source-number" which is 33 chars long.
+ */
+#define OF_PROPNAME_LEN_MAX 64
+
+#define VOF_MAX_PATH        256
+#define VOF_MAX_SETPROPLEN  2048
+#define VOF_MAX_METHODLEN   256
+#define VOF_MAX_FORTHCODE   256
+#define VOF_VTY_BUF_SIZE    256
+
+typedef struct {
+    uint64_t start;
+    uint64_t size;
+} OfClaimed;
+
+typedef struct {
+    char *path; /* the path used to open the instance */
+    uint32_t phandle;
+} OfInstance;
+
+#define VOF_MEM_READ(pa, buf, size) \
+    address_space_read_full(&address_space_memory, \
+    (pa), MEMTXATTRS_UNSPECIFIED, (buf), (size))
+#define VOF_MEM_WRITE(pa, buf, size) \
+    address_space_write(&address_space_memory, \
+    (pa), MEMTXATTRS_UNSPECIFIED, (buf), (size))
+
+static int readstr(hwaddr pa, char *buf, int size)
+{
+    if (VOF_MEM_READ(pa, buf, size) != MEMTX_OK) {
+        return -1;
+    }
+    if (strnlen(buf, size) == size) {
+        buf[size - 1] = '\0';
+        trace_vof_error_str_truncated(buf, size);
+        return -1;
+    }
+    return 0;
+}
+
+static bool cmpservice(const char *s, unsigned nargs, unsigned nret,
+                       const char *s1, unsigned nargscheck, unsigned nretcheck)
+{
+    if (strcmp(s, s1)) {
+        return false;
+    }
+    if ((nargscheck && (nargs != nargscheck)) ||
+        (nretcheck && (nret != nretcheck))) {
+        trace_vof_error_param(s, nargscheck, nretcheck, nargs, nret);
+        return false;
+    }
+
+    return true;
+}
+
+static void prop_format(char *tval, int tlen, const void *prop, int len)
+{
+    int i;
+    const unsigned char *c;
+    char *t;
+    const char bin[] = "...";
+
+    for (i = 0, c = prop; i < len; ++i, ++c) {
+        if (*c == '\0' && i == len - 1) {
+            strncpy(tval, prop, tlen - 1);
+            return;
+        }
+        if (*c < 0x20 || *c >= 0x80) {
+            break;
+        }
+    }
+
+    for (i = 0, c = prop, t = tval; i < len; ++i, ++c) {
+        if (t >= tval + tlen - sizeof(bin) - 1 - 2 - 1) {
+            strcpy(t, bin);
+            return;
+        }
+        if (i && i % 4 == 0 && i != len - 1) {
+            strcat(t, " ");
+            ++t;
+        }
+        t += sprintf(t, "%02X", *c & 0xFF);
+    }
+}
+
+static int get_path(const void *fdt, int offset, char *buf, int len)
+{
+    int ret;
+
+    ret = fdt_get_path(fdt, offset, buf, len - 1);
+    if (ret < 0) {
+        return ret;
+    }
+
+    buf[len - 1] = '\0';
+
+    return strlen(buf) + 1;
+}
+
+static int phandle_to_path(const void *fdt, uint32_t ph, char *buf, int len)
+{
+    int ret;
+
+    ret = fdt_node_offset_by_phandle(fdt, ph);
+    if (ret < 0) {
+        return ret;
+    }
+
+    return get_path(fdt, ret, buf, len);
+}
+
+static uint32_t vof_finddevice(const void *fdt, uint32_t nodeaddr)
+{
+    char fullnode[VOF_MAX_PATH];
+    uint32_t ret = -1;
+    int offset;
+
+    if (readstr(nodeaddr, fullnode, sizeof(fullnode))) {
+        return (uint32_t) ret;
+    }
+
+    offset = fdt_path_offset(fdt, fullnode);
+    if (offset >= 0) {
+        ret = fdt_get_phandle(fdt, offset);
+    }
+    trace_vof_finddevice(fullnode, ret);
+    return (uint32_t) ret;
+}

The Linux init function that runs on pegasos2 here:

https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/tree/arch/powerpc/kernel/prom_init.c?h=v4.14.234#n2658

calls finddevice once with isa@c and next with isa@C (small and capital C) both of which works with the board firmware but with vof the comparison is case sensitive and one of these fails so I can't make it work. I don't know if this is a problem in libfdt or the vof_finddevice above should do something else to get case insensitive comparison.

+
+static const void *getprop(const void *fdt, int nodeoff, const char *propname,
+                           int *proplen, bool *write0)
+{
+    const char *unit, *prop;
+
+    /*
+     * The "name" property is not actually stored as a property in the FDT,
+     * we emulate it by returning a pointer to the node's name and adjust
+     * proplen to include only the name but not the unit.
+     */
+    if (strcmp(propname, "name") == 0) {
+        prop = fdt_get_name(fdt, nodeoff, proplen);
+        if (!prop) {
+            *proplen = 0;
+            return NULL;
+        }
+
+        unit = memchr(prop, '@', *proplen);
+        if (unit) {
+            *proplen = unit - prop;
+        }
+        *proplen += 1;
+
+        /*
+         * Since it might be cut at "@" and there will be no trailing zero
+         * in the prop buffer, tell the caller to write zero at the end.
+         */
+        if (write0) {
+            *write0 = true;
+        }
+        return prop;
+    }
+
+    if (write0) {
+        *write0 = false;
+    }
+    return fdt_getprop(fdt, nodeoff, propname, proplen);
+}

MorphOS checks the name property of the root node ("/") to decide what platform it runs on so we may need to be able to set this property on / where it should return "bplan,Pegasos2", therefore the above maybe should do getprop first and only generate name property if it's not set (or at least check if we're on the root node and allow setting name property there). (On Macs the root node is named "device-tree" and this was before found to be needed for MorphOS.)

Other than the above two problems, I've found that getting the device tree from vof returns it in reverse order compared to the board firmware if I add it the expected order. This may or may not be a problem but to avoid it I can build the tree in reverse order then it comes out right so unless there's an easy fix this should not cause a problem but may worth a comment somewhere.

Regards,
BALATON Zoltan



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