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| author | Zide Chen <zide.chen@intel.com> | 2019-08-16 16:40:51 -0700 |
|---|---|---|
| committer | Commit Bot <commit-bot@chromium.org> | 2019-08-23 19:49:54 +0000 |
| commit | 4d7fd7f93dcc45cd55ff519c6b6ba5b103c38076 (patch) | |
| tree | 41715796c37d816f51a10a686c759d7036919b34 | |
| parent | 6f9215cecd81947cb5c42e5ad43e1470f7e4e802 (diff) | |
| download | crosvm-4d7fd7f93dcc45cd55ff519c6b6ba5b103c38076.tar crosvm-4d7fd7f93dcc45cd55ff519c6b6ba5b103c38076.tar.gz crosvm-4d7fd7f93dcc45cd55ff519c6b6ba5b103c38076.tar.bz2 crosvm-4d7fd7f93dcc45cd55ff519c6b6ba5b103c38076.tar.lz crosvm-4d7fd7f93dcc45cd55ff519c6b6ba5b103c38076.tar.xz crosvm-4d7fd7f93dcc45cd55ff519c6b6ba5b103c38076.tar.zst crosvm-4d7fd7f93dcc45cd55ff519c6b6ba5b103c38076.zip | |
devices: virtio: set zero length mmio eventfd for VQ notification address
By registering the notify address with Datamatch::AnyLength, KVM is able
to take advantage of KVM_FAST_MMIO_BUS to accelerate eventfd handling.
Seems this doesn't violate the virtio spec because "writing the 16-bit
virtqueue index" refers to the implementation of front-end driver, for
example, Linux's vp_notify() function. While how to handle the VQ index
write in VMM is not covererd by virtio spec. Here Crosvm ensures that
every VQ has dedicated notify address and KVM implements the notification
by eventfd, which should be fine with the spec.
On eve Pixelbook (R77 host kernel 4.4.185), in 5000 samples, on average
the MMIO write vmexit takes 0.96us with fast_mmio enabled, while it takes
3.36us without fast_mmio.
without fast_mmio:
232812.822491: kvm_exit: reason EPT_MISCONFIG rip 0xffffffff986f18ef info 0 0
232812.822492: kvm_emulate_insn: 0:ffffffff986f18ef:66 89 3e (prot64)
232812.822493: vcpu_match_mmio: gva 0xffffb0f4803a1004 gpa 0xe000f004 Write GPA
232812.822493: kvm_mmio: mmio write len 2 gpa 0xe000f004 val 0x1
232812.822495: kvm_entry: vcpu 1
with fast_mmio:
230585.034396: kvm_exit: reason EPT_MISCONFIG rip 0xffffffff9a6f18ef info 0 0
230585.034397: kvm_fast_mmio: fast mmio at gpa 0xe000f004
230585.034397: kvm_entry: vcpu 1
BUG=chromium:993488
TEST=Boot Crostini on eve and run iperf benchmark
TEST=Analysis kernel trace for vmexit handling time
Change-Id: Id1dac22b37490f7026b6c119c85ca9d104a8a3f4
Signed-off-by: Zide Chen <zide.chen@intel.corp-partner.google.com>
Signed-off-by: Sainath Grandhi <sainath.grandhi@intel.corp-partner.google.com>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosvm/+/1762282
Reviewed-by: Daniel Verkamp <dverkamp@chromium.org>
Tested-by: kokoro <noreply+kokoro@google.com>
Commit-Queue: Daniel Verkamp <dverkamp@chromium.org>
| -rw-r--r-- | devices/src/virtio/virtio_pci_device.rs | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/devices/src/virtio/virtio_pci_device.rs b/devices/src/virtio/virtio_pci_device.rs index 2e437b6..7da2e45 100644 --- a/devices/src/virtio/virtio_pci_device.rs +++ b/devices/src/virtio/virtio_pci_device.rs @@ -422,7 +422,7 @@ impl PciDevice for VirtioPciDevice { ( event, notify_base + i as u64 * NOTIFY_OFF_MULTIPLIER as u64, - Datamatch::U16(Some(i as u16)), + Datamatch::AnyLength, ) }) .collect() |