Force virtiofs devices to a single virtio queue (vcpus=1) (#40758)
Add a vcpus=1 token to the virtiofs device-options string so each device exposes a single virtio queue. This bounds the number of concurrent guest-memory apertures the device can request, avoiding the host VID's 512-aperture quota that wsldevicehost otherwise livelocks against when servicing many parallel requests. - Define a shared c_vcpusOption ("vcpus=1") constant in GuestDeviceManager.h, with a TODO to revisit once the devicehost supports multiple shares per device. - HcsVirtualMachine::AddShare and WslCoreVm::AddVirtioFsShare append the swiotlb and vcpus tokens via a small appendOption lambda, covering the fixed-drive, dynamic-add, and remount paths. Both tokens are constant for the VM's lifetime, so duplicates collapse to a single VirtioFsShare map entry. - Bump Microsoft.WSL.DeviceHost to 1.2.34 Co-authored-by: Ben Hillis <benhill@ntdev.microsoft.com>
Asher Kariv committed
Jun 18, 2026 at 17:28 UTC
532422e00279c648c033397ff43c6455d5ffcf40
4 files changed
+30
-11
packages.config
+1
-1
@@ -19,7 +19,7 @@
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<package id="Microsoft.WSL.bsdtar" version="0.0.2-2" />
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<package id="Microsoft.WSL.Dependencies.amd64fre" version="10.0.27820.1000-250318-1700.rs-base2-hyp" targetFramework="native" />
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<package id="Microsoft.WSL.Dependencies.arm64fre" version="10.0.27820.1000-250318-1700.rs-base2-hyp" targetFramework="native" />
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- <package id="Microsoft.WSL.DeviceHost" version="1.2.29-0" />
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+ <package id="Microsoft.WSL.DeviceHost" version="1.2.34-0" />
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<package id="Microsoft.WSL.Kernel" version="6.18.35.1-1" targetFramework="native" />
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<package id="Microsoft.WSL.LinuxSdk" version="1.20.0" targetFramework="native" />
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<package id="Microsoft.WSL.TestData" version="0.4.0" />
src/windows/common/GuestDeviceManager.h
+5
@@ -10,6 +10,11 @@
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inline const std::wstring c_defaultDeviceTag = L"default";
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+// Use vcpus=1 so the device exposes a single virtio queue, bounding concurrent
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+// guest-memory apertures to avoid hitting the host VID's 512-aperture quota.
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+// TODO: revisit when the devicehost supports multiple shares per device.
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+inline const std::wstring c_vcpusOption = L"vcpus=1";
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+
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// These device types and class IDs are implemented by the external wsldevicehost vdev.
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DEFINE_GUID(VIRTIO_FS_DEVICE_ID, 0x872270E1, 0xA899, 0x4AF6, 0xB4, 0x54, 0x71, 0x93, 0x63, 0x44, 0x35, 0xAD); // {872270E1-A899-4AF6-B454-7193634435AD}
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DEFINE_GUID(VIRTIO_FS_ADMIN_CLASS_ID, 0x7E6AD219, 0xD1B3, 0x42D5, 0xB8, 0xEE, 0xD9, 0x63, 0x24, 0xE6, 0x4F, 0xF6); // {7E6AD219-D1B3-42D5-B8EE-D96324E64FF6}
src/windows/service/exe/HcsVirtualMachine.cpp
+11
-4
@@ -587,15 +587,22 @@ try
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else
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{
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std::wstring options = ReadOnly ? L"ro" : L"";
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- if (!m_swiotlbOption.empty())
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- {
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+ auto appendOption = [&options](const std::wstring& option) {
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+ if (option.empty())
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+ {
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+ return;
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+ }
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+
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if (!options.empty())
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{
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options += L";";
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}
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- options += m_swiotlbOption;
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- }
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+ options += option;
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+ };
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+
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+ appendOption(m_swiotlbOption);
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+ appendOption(c_vcpusOption);
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it->second = m_guestDeviceManager->AddGuestDevice(
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VIRTIO_FS_DEVICE_ID,
src/windows/service/exe/WslCoreVm.cpp
+13
-6
@@ -2195,18 +2195,25 @@ std::pair<std::wstring, std::wstring> WslCoreVm::AddVirtioFsShare(_In_ bool Admi
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sharePath = std::filesystem::weakly_canonical(sharePath).wstring();
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- // Append the swiotlb token here so it covers fixed-drive, dynamic add, and remount paths.
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- // Duplicate swiotlb tokens are harmless: VirtioFsShare parses options into a map.
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+ // Append swiotlb and vcpus here to cover the fixed-drive, dynamic add, and remount paths.
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+ // Safe to duplicate: both tokens are constant per VM, and VirtioFsShare collapses repeats into one map entry.
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std::wstring effectiveOptions(Options);
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- if (!m_swiotlbOption.empty())
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- {
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+ auto appendOption = [&effectiveOptions](const std::wstring& option) {
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+ if (option.empty())
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+ {
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+ return;
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+ }
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+
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if (!effectiveOptions.empty())
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{
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effectiveOptions += L';';
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}
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- effectiveOptions += m_swiotlbOption;
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- }
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+ effectiveOptions += option;
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+ };
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+
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+ appendOption(m_swiotlbOption);
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+ appendOption(c_vcpusOption);
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// Check if a matching share already exists.
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bool created = false;