[Qemu-devel] [RFC v3 PATCH 16/45] multi-process: PCI BAR read/write handling for proxy & remote endpoints

[Jagannathan Raman <jag.raman@oracle.com>]

Proxy device object implements handler for PCI BAR writes and reads. The handler
uses BAR_WRITE/BAR_READ message to communicate to the remote process with the BAR address and
value to be written/read.
The remote process implements handler for BAR_WRITE/BAR_READ message.

Signed-off-by: Jagannathan Raman <jag.raman@oracle.com>
Signed-off-by: Elena Ufimtseva <elena.ufimtseva@oracle.com>
Signed-off-by: John G Johnson <john.g.johnson@oracle.com>
---
 hw/proxy/qemu-proxy.c         | 50 +++++++++++++++++++++++++++++
 include/hw/proxy/qemu-proxy.h |  5 +++
 include/io/proxy-link.h       | 12 +++++++
 remote/remote-main.c          | 73 +++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 140 insertions(+)

diff --git a/hw/proxy/qemu-proxy.c b/hw/proxy/qemu-proxy.c
index e5fd4bb..44668bf 100644
--- a/hw/proxy/qemu-proxy.c
+++ b/hw/proxy/qemu-proxy.c
@@ -287,3 +287,53 @@ static void pci_proxy_dev_realize(PCIDevice *device, Error **errp)
     dev->get_proxy_sock = get_proxy_sock;
     dev->init_proxy = init_proxy;
 }
+
+static void send_bar_access_msg(ProxyLinkState *proxy_link, MemoryRegion *mr,
+                                bool write, hwaddr addr, uint64_t *val,
+                                unsigned size, bool memory)
+{
+    ProcMsg msg;
+    int wait;
+
+    memset(&msg, 0, sizeof(ProcMsg));
+
+    msg.bytestream = 0;
+    msg.size = sizeof(msg.data1);
+    msg.data1.bar_access.addr = mr->addr + addr;
+    msg.data1.bar_access.size = size;
+    msg.data1.bar_access.memory = memory;
+
+    if (write) {
+        msg.cmd = BAR_WRITE;
+        msg.data1.bar_access.val = *val;
+    } else {
+        wait = GET_REMOTE_WAIT;
+
+        msg.cmd = BAR_READ;
+        msg.num_fds = 1;
+        msg.fds[0] = wait;
+    }
+
+    proxy_proc_send(proxy_link, &msg, proxy_link->com);
+
+    if (!write) {
+        *val = wait_for_remote(wait);
+        PUT_REMOTE_WAIT(wait);
+    }
+}
+
+void proxy_default_bar_write(PCIProxyDev *dev, MemoryRegion *mr, hwaddr addr,
+                             uint64_t val, unsigned size, bool memory)
+{
+    send_bar_access_msg(dev->proxy_link, mr, true, addr, &val, size, memory);
+}
+
+uint64_t proxy_default_bar_read(PCIProxyDev *dev, MemoryRegion *mr, hwaddr addr,
+                                unsigned size, bool memory)
+{
+    uint64_t val;
+
+    send_bar_access_msg(dev->proxy_link, mr, false, addr, &val, size, memory);
+
+    return val;
+}
diff --git a/include/hw/proxy/qemu-proxy.h b/include/hw/proxy/qemu-proxy.h
index 3b37b65..a951570 100644
--- a/include/hw/proxy/qemu-proxy.h
+++ b/include/hw/proxy/qemu-proxy.h
@@ -77,5 +77,10 @@ typedef struct PCIProxyDevClass {
 
 int remote_spawn(PCIProxyDev *pdev, const char *command, Error **errp);
 
+void proxy_default_bar_write(PCIProxyDev *dev, MemoryRegion *mr, hwaddr addr,
+                             uint64_t val, unsigned size, bool memory);
+
+uint64_t proxy_default_bar_read(PCIProxyDev *dev, MemoryRegion *mr, hwaddr addr,
+                                unsigned size, bool memory);
 
 #endif /* QEMU_PROXY_H */
diff --git a/include/io/proxy-link.h b/include/io/proxy-link.h
index 0785394..2c290b2 100644
--- a/include/io/proxy-link.h
+++ b/include/io/proxy-link.h
@@ -56,6 +56,8 @@ typedef struct ProxyLinkState ProxyLinkState;
  * CONF_READ        PCI config. space read
  * CONF_WRITE       PCI config. space write
  * SYNC_SYSMEM      Shares QEMU's RAM with remote device's RAM
+ * BAR_WRITE        Writes to PCI BAR region
+ * BAR_READ         Reads from PCI BAR region
  *
  */
 typedef enum {
@@ -63,6 +65,8 @@ typedef enum {
     CONF_READ,
     CONF_WRITE,
     SYNC_SYSMEM,
+    BAR_WRITE,
+    BAR_READ,
     MAX,
 } proc_cmd_t;
 
@@ -85,6 +89,13 @@ typedef struct {
 } sync_sysmem_msg_t;
 
 typedef struct {
+    hwaddr addr;
+    uint64_t val;
+    unsigned size;
+    bool memory;
+} bar_access_msg_t;
+
+typedef struct {
     proc_cmd_t cmd;
     int bytestream;
     size_t size;
@@ -93,6 +104,7 @@ typedef struct {
     union {
         uint64_t u64;
         sync_sysmem_msg_t sync_sysmem;
+        bar_access_msg_t bar_access;
     } data1;
 
     int fds[REMOTE_MAX_FDS];
diff --git a/remote/remote-main.c b/remote/remote-main.c
index 93b2d36..43fe50a 100644
--- a/remote/remote-main.c
+++ b/remote/remote-main.c
@@ -45,6 +45,7 @@
 #include "qemu/config-file.h"
 #include "sysemu/sysemu.h"
 #include "block/block.h"
+#include "exec/memattrs.h"
 
 static ProxyLinkState *proxy_link;
 PCIDevice *remote_pci_dev;
@@ -75,6 +76,66 @@ static void process_config_read(ProcMsg *msg)
     PUT_REMOTE_WAIT(wait);
 }
 
+/* TODO: confirm memtx attrs. */
+static void process_bar_write(ProcMsg *msg, Error **errp)
+{
+    bar_access_msg_t *bar_access = &msg->data1.bar_access;
+    AddressSpace *as =
+        bar_access->memory ? &address_space_memory : &address_space_io;
+    MemTxResult res;
+
+    res = address_space_rw(as, bar_access->addr, MEMTXATTRS_UNSPECIFIED,
+                           (uint8_t *)&bar_access->val, bar_access->size, true);
+
+    if (res != MEMTX_OK) {
+        error_setg(errp, "Could not perform address space write operation,"
+                   " inaccessible address: %lx.", bar_access->addr);
+    }
+}
+
+static void process_bar_read(ProcMsg *msg, Error **errp)
+{
+    bar_access_msg_t *bar_access = &msg->data1.bar_access;
+    AddressSpace *as;
+    int wait = msg->fds[0];
+    MemTxResult res;
+    uint64_t val = 0;
+
+    as = bar_access->memory ? &address_space_memory : &address_space_io;
+
+    assert(bar_access->size <= sizeof(uint64_t));
+
+    res = address_space_rw(as, bar_access->addr, MEMTXATTRS_UNSPECIFIED,
+                           (uint8_t *)&val, bar_access->size, false);
+
+    if (res != MEMTX_OK) {
+        error_setg(errp, "Could not perform address space read operation,"
+                   " inaccessible address: %lx.", bar_access->addr);
+        val = (uint64_t)-1;
+        goto fail;
+    }
+
+    switch (bar_access->size) {
+    case 4:
+        val = *((uint32_t *)&val);
+        break;
+    case 2:
+        val = *((uint16_t *)&val);
+        break;
+    case 1:
+        val = *((uint8_t *)&val);
+        break;
+    default:
+        error_setg(errp, "Invalid PCI BAR read size");
+        return;
+    }
+
+fail:
+    notify_proxy(wait, val);
+
+    PUT_REMOTE_WAIT(wait);
+}
+
 static void process_msg(GIOCondition cond, ProcChannel *chan)
 {
     ProcMsg *msg = NULL;
@@ -101,6 +162,18 @@ static void process_msg(GIOCondition cond, ProcChannel *chan)
     case CONF_READ:
         process_config_read(msg);
         break;
+    case BAR_WRITE:
+        process_bar_write(msg, &err);
+        if (err) {
+            goto finalize_loop;
+        }
+        break;
+    case BAR_READ:
+        process_bar_read(msg, &err);
+        if (err) {
+            goto finalize_loop;
+        }
+        break;
     default:
         error_setg(&err, "Unknown command");
         goto finalize_loop;
-- 
1.8.3.1