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Re: [PATCH v3] fuzz: map all BARs and enable PCI devices


From: Paolo Bonzini
Subject: Re: [PATCH v3] fuzz: map all BARs and enable PCI devices
Date: Mon, 21 Dec 2020 19:27:31 +0100
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.5.0

On 21/12/20 19:12, Alexander Bulekov wrote:
Prior to this patch, the fuzzer found inputs to map PCI device BARs and
enable the device. While it is nice that the fuzzer can do this, it
added significant overhead, since the fuzzer needs to map all the
BARs (regenerating the memory topology), at the start of each input.
With this patch, we do this once, before fuzzing, mitigating some of
this overhead.

Signed-off-by: Alexander Bulekov <alxndr@bu.edu>
Reviewed-by: Darren Kenny <darren.kenny@oracle.com>
---

v3: Plug the memory-leak pointed out by Thomas:
     https://gitlab.com/huth/qemu/-/jobs/920543745#L309

  tests/qtest/fuzz/generic_fuzz.c | 24 ++++++++++++++++++++++++
  1 file changed, 24 insertions(+)

diff --git a/tests/qtest/fuzz/generic_fuzz.c b/tests/qtest/fuzz/generic_fuzz.c
index 07ad690683..be76d47d2d 100644
--- a/tests/qtest/fuzz/generic_fuzz.c
+++ b/tests/qtest/fuzz/generic_fuzz.c
@@ -16,6 +16,7 @@
#include "hw/core/cpu.h"
  #include "tests/qtest/libqos/libqtest.h"
+#include "tests/qtest/libqos/pci-pc.h"
  #include "fuzz.h"
  #include "fork_fuzz.h"
  #include "exec/address-spaces.h"
@@ -762,10 +763,29 @@ static int locate_fuzz_objects(Object *child, void 
*opaque)
      return 0;
  }
+
+static void pci_enum(gpointer pcidev, gpointer bus)
+{
+    PCIDevice *dev = pcidev;
+    QPCIDevice *qdev;
+    int i;
+
+    qdev = qpci_device_find(bus, dev->devfn);
+    g_assert(qdev != NULL);
+    for (i = 0; i < 6; i++) {
+        if (dev->io_regions[i].size) {
+            qpci_iomap(qdev, i, NULL);
+        }
+    }
+    qpci_device_enable(qdev);
+    g_free(qdev);
+}
+
  static void generic_pre_fuzz(QTestState *s)
  {
      GHashTableIter iter;
      MemoryRegion *mr;
+    QPCIBus *pcibus;
      char **result;
if (!getenv("QEMU_FUZZ_OBJECTS")) {
@@ -810,6 +830,10 @@ static void generic_pre_fuzz(QTestState *s)
          exit(1);
      }
+ pcibus = qpci_new_pc(s, NULL);
+    g_ptr_array_foreach(fuzzable_pci_devices, pci_enum, pcibus);
+    qpci_free_pc(pcibus);
+
      counter_shm_init();
  }

Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>




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