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[Qemu-devel] [PATCH] memory: emulate ioeventfd
From: |
Pavel Fedin |
Subject: |
[Qemu-devel] [PATCH] memory: emulate ioeventfd |
Date: |
Fri, 20 Nov 2015 12:37:16 +0300 |
The ioeventfd mechanism is used by vhost, dataplane, and virtio-pci to
turn guest MMIO/PIO writes into eventfd file descriptor events. This
allows arbitrary threads to be notified when the guest writes to a
specific MMIO/PIO address.
qtest and TCG do not support ioeventfd because memory writes are not
checked against registered ioeventfds in QEMU. This patch implements
this in memory_region_dispatch_write() so qtest can use ioeventfd.
Also this patch fixes vhost aborting on some misconfigured old kernels
like 3.18.0 on ARM. It is possible to explicitly enable CONFIG_EVENTFD
in expert settings, while MMIO binding support in KVM will still be
missing.
Signed-off-by: Stefan Hajnoczi <address@hidden>
Signed-off-by: Pavel Fedin <address@hidden>
---
RFC => PATCH:
- Add !kvm_eventfds_enabled() conditions to bypass eventfd injection when not
needed
- Renamed "ioeventfd" to "eventfd", just to make words shorter
- Add a one-shot warning about missing MMIO bindings in KVM
---
kvm-all.c | 6 ++++--
memory.c | 42 ++++++++++++++++++++++++++++++++++++++++++
2 files changed, 46 insertions(+), 2 deletions(-)
diff --git a/kvm-all.c b/kvm-all.c
index ddb007a..70f5cec 100644
--- a/kvm-all.c
+++ b/kvm-all.c
@@ -1633,8 +1633,10 @@ static int kvm_init(MachineState *ms)
kvm_state = s;
- s->memory_listener.listener.eventfd_add = kvm_mem_ioeventfd_add;
- s->memory_listener.listener.eventfd_del = kvm_mem_ioeventfd_del;
+ if (kvm_eventfds_allowed) {
+ s->memory_listener.listener.eventfd_add = kvm_mem_ioeventfd_add;
+ s->memory_listener.listener.eventfd_del = kvm_mem_ioeventfd_del;
+ }
s->memory_listener.listener.coalesced_mmio_add = kvm_coalesce_mmio_region;
s->memory_listener.listener.coalesced_mmio_del =
kvm_uncoalesce_mmio_region;
diff --git a/memory.c b/memory.c
index e193658..4d138fb 100644
--- a/memory.c
+++ b/memory.c
@@ -18,12 +18,14 @@
#include "exec/ioport.h"
#include "qapi/visitor.h"
#include "qemu/bitops.h"
+#include "qemu/error-report.h"
#include "qom/object.h"
#include "trace.h"
#include <assert.h>
#include "exec/memory-internal.h"
#include "exec/ram_addr.h"
+#include "sysemu/kvm.h"
#include "sysemu/sysemu.h"
//#define DEBUG_UNASSIGNED
@@ -1141,6 +1143,32 @@ MemTxResult memory_region_dispatch_read(MemoryRegion *mr,
return r;
}
+/* Return true if an eventfd was signalled */
+static bool memory_region_dispatch_write_eventfds(MemoryRegion *mr,
+ hwaddr addr,
+ uint64_t data,
+ unsigned size,
+ MemTxAttrs attrs)
+{
+ MemoryRegionIoeventfd ioeventfd = {
+ .addr = addrrange_make(int128_make64(addr), int128_make64(size)),
+ .data = data,
+ };
+ unsigned i;
+
+ for (i = 0; i < mr->ioeventfd_nb; i++) {
+ ioeventfd.match_data = mr->ioeventfds[i].match_data;
+ ioeventfd.e = mr->ioeventfds[i].e;
+
+ if (memory_region_ioeventfd_equal(ioeventfd, mr->ioeventfds[i])) {
+ event_notifier_set(ioeventfd.e);
+ return true;
+ }
+ }
+
+ return false;
+}
+
MemTxResult memory_region_dispatch_write(MemoryRegion *mr,
hwaddr addr,
uint64_t data,
@@ -1154,6 +1182,11 @@ MemTxResult memory_region_dispatch_write(MemoryRegion
*mr,
adjust_endianness(mr, &data, size);
+ if ((!kvm_eventfds_enabled()) &&
+ memory_region_dispatch_write_eventfds(mr, addr, data, size, attrs)) {
+ return MEMTX_OK;
+ }
+
if (mr->ops->write) {
return access_with_adjusted_size(addr, &data, size,
mr->ops->impl.min_access_size,
@@ -1672,6 +1705,8 @@ void memory_region_clear_global_locking(MemoryRegion *mr)
mr->global_locking = false;
}
+static bool userspace_eventfd_warning;
+
void memory_region_add_eventfd(MemoryRegion *mr,
hwaddr addr,
unsigned size,
@@ -1688,6 +1723,13 @@ void memory_region_add_eventfd(MemoryRegion *mr,
};
unsigned i;
+ if (kvm_enabled() && (!(kvm_eventfds_enabled() ||
+ userspace_eventfd_warning))) {
+ userspace_eventfd_warning = true;
+ error_report("Using eventfd without MMIO binding in KVM. "
+ "Suboptimal performance expected");
+ }
+
if (size) {
adjust_endianness(mr, &mrfd.data, size);
}
--
1.9.5.msysgit.0
- [Qemu-devel] [PATCH] memory: emulate ioeventfd,
Pavel Fedin <=