[PATCH v1 1/9] hw: encode accessing CPU index in MemTxAttrs

[Alex Bennée]

We currently have hacks across the hw/ to reference current_cpu to
work out what the current accessing CPU is. This breaks in some cases
including using gdbstub to access HW state. As we have MemTxAttrs to
describe details about the access lets extend it to mention if this is
a CPU access and which one it is.

There are a number of places we need to fix up including:

  CPU helpers directly calling address_space_*() fns
  models in hw/ fishing the data out of current_cpu

I'll start addressing some of these in following patches.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>

---
v2
  - use separate field cpu_index
  - bool for requester_is_cpu
---
 include/exec/memattrs.h |  4 ++++
 accel/tcg/cputlb.c      | 22 ++++++++++++++++------
 hw/core/cpu-sysemu.c    | 17 +++++++++++++----
 3 files changed, 33 insertions(+), 10 deletions(-)

diff --git a/include/exec/memattrs.h b/include/exec/memattrs.h
index 9fb98bc1ef..e83a993c21 100644
--- a/include/exec/memattrs.h
+++ b/include/exec/memattrs.h
@@ -43,6 +43,10 @@ typedef struct MemTxAttrs {
      * (see MEMTX_ACCESS_ERROR).
      */
     unsigned int memory:1;
+    /* Requester is CPU (or as CPU, e.g. debug) */
+    bool requester_is_cpu:1;
+    /* cpu_index (if requester_is_cpu) */
+    unsigned int cpu_index:16;
     /* Requester ID (for MSI for example) */
     unsigned int requester_id:16;
     /* Invert endianness for this page */
diff --git a/accel/tcg/cputlb.c b/accel/tcg/cputlb.c
index 8fad2d9b83..5d88569eb5 100644
--- a/accel/tcg/cputlb.c
+++ b/accel/tcg/cputlb.c
@@ -1340,8 +1340,13 @@ static uint64_t io_readx(CPUArchState *env, 
CPUIOTLBEntry *iotlbentry,
     uint64_t val;
     bool locked = false;
     MemTxResult r;
+    MemTxAttrs attrs = iotlbentry->attrs;
 
-    section = iotlb_to_section(cpu, iotlbentry->addr, iotlbentry->attrs);
+    /* encode the accessing CPU */
+    attrs.requester_is_cpu = 1;
+    attrs.cpu_index = cpu->cpu_index;
+
+    section = iotlb_to_section(cpu, iotlbentry->addr, attrs);
     mr = section->mr;
     mr_offset = (iotlbentry->addr & TARGET_PAGE_MASK) + addr;
     cpu->mem_io_pc = retaddr;
@@ -1353,14 +1358,14 @@ static uint64_t io_readx(CPUArchState *env, 
CPUIOTLBEntry *iotlbentry,
         qemu_mutex_lock_iothread();
         locked = true;
     }
-    r = memory_region_dispatch_read(mr, mr_offset, &val, op, 
iotlbentry->attrs);
+    r = memory_region_dispatch_read(mr, mr_offset, &val, op, attrs);
     if (r != MEMTX_OK) {
         hwaddr physaddr = mr_offset +
             section->offset_within_address_space -
             section->offset_within_region;
 
         cpu_transaction_failed(cpu, physaddr, addr, memop_size(op), 
access_type,
-                               mmu_idx, iotlbentry->attrs, r, retaddr);
+                               mmu_idx, attrs, r, retaddr);
     }
     if (locked) {
         qemu_mutex_unlock_iothread();
@@ -1395,8 +1400,13 @@ static void io_writex(CPUArchState *env, CPUIOTLBEntry 
*iotlbentry,
     MemoryRegion *mr;
     bool locked = false;
     MemTxResult r;
+    MemTxAttrs attrs = iotlbentry->attrs;
+
+    /* encode the accessing CPU */
+    attrs.requester_is_cpu = true;
+    attrs.cpu_index = cpu->cpu_index;
 
-    section = iotlb_to_section(cpu, iotlbentry->addr, iotlbentry->attrs);
+    section = iotlb_to_section(cpu, iotlbentry->addr, attrs);
     mr = section->mr;
     mr_offset = (iotlbentry->addr & TARGET_PAGE_MASK) + addr;
     if (!cpu->can_do_io) {
@@ -1414,14 +1424,14 @@ static void io_writex(CPUArchState *env, CPUIOTLBEntry 
*iotlbentry,
         qemu_mutex_lock_iothread();
         locked = true;
     }
-    r = memory_region_dispatch_write(mr, mr_offset, val, op, 
iotlbentry->attrs);
+    r = memory_region_dispatch_write(mr, mr_offset, val, op, attrs);
     if (r != MEMTX_OK) {
         hwaddr physaddr = mr_offset +
             section->offset_within_address_space -
             section->offset_within_region;
 
         cpu_transaction_failed(cpu, physaddr, addr, memop_size(op),
-                               MMU_DATA_STORE, mmu_idx, iotlbentry->attrs, r,
+                               MMU_DATA_STORE, mmu_idx, attrs, r,
                                retaddr);
     }
     if (locked) {
diff --git a/hw/core/cpu-sysemu.c b/hw/core/cpu-sysemu.c
index 00253f8929..cdabc577d2 100644
--- a/hw/core/cpu-sysemu.c
+++ b/hw/core/cpu-sysemu.c
@@ -51,13 +51,22 @@ hwaddr cpu_get_phys_page_attrs_debug(CPUState *cpu, vaddr 
addr,
                                      MemTxAttrs *attrs)
 {
     CPUClass *cc = CPU_GET_CLASS(cpu);
+    MemTxAttrs local = { };
+    hwaddr res;
 
     if (cc->sysemu_ops->get_phys_page_attrs_debug) {
-        return cc->sysemu_ops->get_phys_page_attrs_debug(cpu, addr, attrs);
+        res = cc->sysemu_ops->get_phys_page_attrs_debug(cpu, addr, &local);
+    } else {
+        /* Fallback for CPUs which don't implement the _attrs_ hook */
+        local = MEMTXATTRS_UNSPECIFIED;
+        res = cc->sysemu_ops->get_phys_page_debug(cpu, addr);
     }
-    /* Fallback for CPUs which don't implement the _attrs_ hook */
-    *attrs = MEMTXATTRS_UNSPECIFIED;
-    return cc->sysemu_ops->get_phys_page_debug(cpu, addr);
+
+    /* debug access is treated as though it came from the CPU */
+    local.requester_is_cpu = 1;
+    local.cpu_index = cpu->cpu_index;
+    *attrs = local;
+    return res;
 }
 
 hwaddr cpu_get_phys_page_debug(CPUState *cpu, vaddr addr)
-- 
2.34.1