[v4] accel: Preparatory cleanups for split-accel

[PATCH v4 60/65] system/memory: Restrict eventfd dispatch_write() to emulators

Philippe Mathieu-Daudé posted 65 patches 4 months, 2 weeks ago

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Maintainers: Richard Henderson <richard.henderson@linaro.org>, Paolo Bonzini <pbonzini@redhat.com>, Cameron Esfahani <dirty@apple.com>, Roman Bolshakov <rbolshakov@ddn.com>, Phil Dennis-Jordan <phil@philjordan.eu>, Mads Ynddal <mads@ynddal.dk>, Fabiano Rosas <farosas@suse.de>, Laurent Vivier <lvivier@redhat.com>, Stefano Stabellini <sstabellini@kernel.org>, Anthony PERARD <anthony@xenproject.org>, Paul Durrant <paul@xen.org>, "Edgar E. Iglesias" <edgar.iglesias@gmail.com>, Warner Losh <imp@bsdimp.com>, Kyle Evans <kevans@freebsd.org>, "Alex Bennée" <alex.bennee@linaro.org>, "Philippe Mathieu-Daudé" <philmd@linaro.org>, "Dr. David Alan Gilbert" <dave@treblig.org>, Eduardo Habkost <eduardo@habkost.net>, Marcel Apfelbaum <marcel.apfelbaum@gmail.com>, Yanan Wang <wangyanan55@huawei.com>, Zhao Liu <zhao1.liu@intel.com>, Reinoud Zandijk <reinoud@netbsd.org>, Sunil Muthuswamy <sunilmut@microsoft.com>, Eric Blake <eblake@redhat.com>, Markus Armbruster <armbru@redhat.com>, Michael Roth <michael.roth@amd.com>, Peter Xu <peterx@redhat.com>, David Hildenbrand <david@redhat.com>, Peter Maydell <peter.maydell@linaro.org>, Alexander Graf <agraf@csgraf.de>

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[PATCH v4 60/65] system/memory: Restrict eventfd dispatch_write() to emulators

Posted by Philippe Mathieu-Daudé 4 months, 2 weeks ago

Commit 8c56c1a592b ("memory: emulate ioeventfd") added a !KVM
check because the only accelerator available back then were TCG,
QTest and KVM. Then commit 126e7f78036 ("kvm: require
KVM_CAP_IOEVENTFD and KVM_CAP_IOEVENTFD_ANY_LENGTH") suggested
'!KVM' check should be '(TCG || QTest)'. Later more accelerator
were added. Implement the suggestion as a safety measure, not
dispatching to eventfd when hardware accelerator is used.

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
---
 system/memory.c | 9 ++-------
 1 file changed, 2 insertions(+), 7 deletions(-)

diff --git a/system/memory.c b/system/memory.c
index e8d9b15b28f..b072a6bef83 100644
--- a/system/memory.c
+++ b/system/memory.c
@@ -25,7 +25,7 @@
 #include "qom/object.h"
 #include "trace.h"
 #include "system/ram_addr.h"
-#include "system/kvm.h"
+#include "system/qtest.h"
 #include "system/runstate.h"
 #include "system/tcg.h"
 #include "qemu/accel.h"
@@ -1530,12 +1530,7 @@ MemTxResult memory_region_dispatch_write(MemoryRegion *mr,
 
     adjust_endianness(mr, &data, op);
 
-    /*
-     * FIXME: it's not clear why under KVM the write would be processed
-     * directly, instead of going through eventfd.  This probably should
-     * test "tcg_enabled() || qtest_enabled()", or should just go away.
-     */
-    if (!kvm_enabled() &&
+    if ((tcg_enabled() || qtest_enabled()) &&
         memory_region_dispatch_write_eventfds(mr, addr, data, size, attrs)) {
         return MEMTX_OK;
     }
-- 
2.49.0