The PAPR interface defines a hypercall to pass high-quality
hardware generated random numbers to guests. Recent kernels can
already provide this hypercall to the guest if the right hardware
random number generator is available. But in case the user wants
to use another source like EGD, or QEMU is running with an older
kernel, we should also have this call in QEMU, so that guests that
do not support virtio-rng yet can get good random numbers, too.
This patch now adds a new pseude-device to QEMU that either
directly provides this hypercall to the guest or is able to
enable the in-kernel hypercall if available. The in-kernel
hypercall can be enabled with the use-kvm property, e.g.:
qemu-system-ppc64 -device spapr-rng,use-kvm=true
For handling the hypercall in QEMU instead, a RngBackend is required
since the hypercall should provide "good" random data instead of
pseudo-random (like from a "simple" library function like rand()
or g_random_int()). Since there are multiple RngBackends available,
the user must select an appropriate backend via the "backend"
property of the device, e.g.:
qemu-system-ppc64 -object rng-random,filename=/dev/hwrng,id=rng0 \
-device spapr-rng,backend=rng0 ...
See http://wiki.qemu-project.org/Features-Done/VirtIORNG for
other example of specifying RngBackends.
Signed-off-by: Thomas Huth
---
v3:
- Completely reworked the patch set accordingly to discussion
on the mailing list, so that the code is now encapsulated
as a QEMU device in a separate file.
hw/ppc/Makefile.objs | 2 +-
hw/ppc/spapr.c | 8 +++
hw/ppc/spapr_rng.c | 178 +
include/hw/ppc/spapr.h | 4 ++
target-ppc/kvm.c | 9 +++
target-ppc/kvm_ppc.h | 5 ++
6 files changed, 205 insertions(+), 1 deletion(-)
create mode 100644 hw/ppc/spapr_rng.c
diff --git a/hw/ppc/Makefile.objs b/hw/ppc/Makefile.objs
index c8ab06e..c1ffc77 100644
--- a/hw/ppc/Makefile.objs
+++ b/hw/ppc/Makefile.objs
@@ -3,7 +3,7 @@ obj-y += ppc.o ppc_booke.o
# IBM pSeries (sPAPR)
obj-$(CONFIG_PSERIES) += spapr.o spapr_vio.o spapr_events.o
obj-$(CONFIG_PSERIES) += spapr_hcall.o spapr_iommu.o spapr_rtas.o
-obj-$(CONFIG_PSERIES) += spapr_pci.o spapr_rtc.o spapr_drc.o
+obj-$(CONFIG_PSERIES) += spapr_pci.o spapr_rtc.o spapr_drc.o spapr_rng.o
ifeq ($(CONFIG_PCI)$(CONFIG_PSERIES)$(CONFIG_LINUX), yyy)
obj-y += spapr_pci_vfio.o
endif
diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
index bf0c64f..34e7d24 100644
--- a/hw/ppc/spapr.c
+++ b/hw/ppc/spapr.c
@@ -768,6 +768,14 @@ static void spapr_finalize_fdt(sPAPRMachineState *spapr,
exit(1);
}
+if (object_resolve_path_type("", TYPE_SPAPR_RNG, NULL)) {
+ret = spapr_rng_populate_dt(fdt);
+if (ret < 0) {
+fprintf(stderr, "couldn't setup rng device in fdt\n");
+exit(1);
+}
+}
+
QLIST_FOREACH(phb, &spapr->phbs, list) {
ret = spapr_populate_pci_dt(phb, PHANDLE_XICP, fdt);
}
diff --git a/hw/ppc/spapr_rng.c b/hw/ppc/spapr_rng.c
new file mode 100644
index 000..d4923bc
--- /dev/null
+++ b/hw/ppc/spapr_rng.c
@@ -0,0 +1,178 @@
+/*
+ * QEMU sPAPR random number generator "device" for H_RANDOM hypercall
+ *
+ * Copyright 2015 Thomas Huth, Red Hat Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License,
+ * or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see .
+ */
+
+#include "qemu/error-report.h"
+#include "sysemu/sysemu.h"
+#include "sysemu/device_tree.h"
+#include "sysemu/rng.h"
+#include "hw/ppc/spapr.h"
+#include "kvm_ppc.h"
+
+#define SPAPR_RNG(obj) \
+OBJECT_CHECK(sPAPRRngState, (obj), TYPE_SPAPR_RNG)
+
+typedef struct sPAPRRngState {
+/*< private >*/
+DeviceState ds;
+RngBackend *backend;
+bool use_kvm;
+} sPAPRRngState;
+
+typedef struct HRandomData {
+QemuSemaphore sem;
+union {
+uint64_t v64;
+uint8_t v8[8];
+} val;
+int received;
+} HRandomData;
+
+/* Callback function for the RngBackend */
+static void random_recv(void *dest, const void *src, size_t size)
+{
+HRandomData *hrdp = dest;
+
+if (src && size > 0) {
+assert(size + hrdp->received <= sizeof(hrdp->val.v8));
+memcpy(&hrdp->val.v8[hrdp->received], src, size);
+hrdp->received += size;
+}
+
+qemu_sem_post(&hrdp->sem);
+}
+
+/* Handler for the H_RANDOM hypercall */
+static target_ulong h_random(PowerPCCPU *cpu, sPAPRMachineState *spapr
