KVM: Don't pre-reserve xarray entries when storing empty/NULL attributesgrafted

Skip the xarray reservation loop when clearing all memory attributes, as
storing NULL only erases the entry and never needs to allocate, so no
reservation (and no cleanup of a failed one) is required in that case.

Suggested-by: Sean Christopherson <seanjc@google.com>
Cc: David Ballesteros <davimaba.v@proton.me>
Signed-off-by: Zeng Chi <zengchi@kylinos.cn>
Link: https://patch.msgid.link/20260921102442.1232375-1-zeng_chi911@163.com
[sean: split to separate patch]
Signed-off-by: Sean Christopherson <seanjc@google.com>

1 files changed, 103 insertions, 0 deletions

diff --git a/drivers/iommu/intel/Kconfig b/drivers/iommu/intel/Kconfig
new file mode 100644
index 000000000..5471f814e
--- /dev/null
+++ b/drivers/iommu/intel/Kconfig
@@ -0,0 +1,103 @@
+# SPDX-License-Identifier: GPL-2.0-only
+# Intel IOMMU support
+config DMAR_TABLE
+	bool
+
+config DMAR_PERF
+	bool
+
+config DMAR_DEBUG
+	bool
+
+config INTEL_IOMMU
+	bool "Support for Intel IOMMU using DMA Remapping Devices"
+	depends on PCI_MSI && ACPI && X86
+	select IOMMU_API
+	select GENERIC_PT
+	select IOMMU_PT
+	select IOMMU_PT_X86_64
+	select IOMMU_PT_VTDSS
+	select IOMMU_IOVA
+	select IOMMU_IOPF
+	select IOMMUFD_DRIVER if IOMMUFD
+	select NEED_DMA_MAP_STATE
+	select DMAR_TABLE
+	select SWIOTLB
+	select PCI_ATS
+	select PCI_PRI
+	select PCI_PASID
+	help
+	  DMA remapping (DMAR) devices support enables independent address
+	  translations for Direct Memory Access (DMA) from devices.
+	  These DMA remapping devices are reported via ACPI tables
+	  and include PCI device scope covered by these DMA
+	  remapping devices.
+
+if INTEL_IOMMU
+
+config INTEL_IOMMU_DEBUGFS
+	bool "Export Intel IOMMU internals in Debugfs"
+	depends on IOMMU_DEBUGFS
+	select DMAR_PERF
+	select DMAR_DEBUG
+	help
+	  !!!WARNING!!!
+
+	  DO NOT ENABLE THIS OPTION UNLESS YOU REALLY KNOW WHAT YOU ARE DOING!!!
+
+	  Expose Intel IOMMU internals in Debugfs.
+
+	  This option is -NOT- intended for production environments, and should
+	  only be enabled for debugging Intel IOMMU.
+
+config INTEL_IOMMU_SVM
+	bool "Support for Shared Virtual Memory with Intel IOMMU"
+	depends on X86_64
+	select MMU_NOTIFIER
+	select IOMMU_SVA
+	help
+	  Shared Virtual Memory (SVM) provides a facility for devices
+	  to access DMA resources through process address space by
+	  means of a Process Address Space ID (PASID).
+
+config INTEL_IOMMU_DEFAULT_ON
+	bool "Enable Intel DMA Remapping Devices by default"
+	default y
+	help
+	  Selecting this option will enable a DMAR device at boot time if
+	  one is found. If this option is not selected, DMAR support can
+	  be enabled by passing intel_iommu=on to the kernel.
+
+config INTEL_IOMMU_FLOPPY_WA
+	def_bool y
+	depends on X86 && BLK_DEV_FD
+	help
+	  Floppy disk drivers are known to bypass DMA API calls
+	  thereby failing to work when IOMMU is enabled. This
+	  workaround will setup a 1:1 mapping for the first
+	  16MiB to make floppy (an ISA device) work.
+
+config INTEL_IOMMU_SCALABLE_MODE_DEFAULT_ON
+	bool "Enable Intel IOMMU scalable mode by default"
+	default y
+	help
+	  Selecting this option will enable by default the scalable mode if
+	  hardware presents the capability. The scalable mode is defined in
+	  VT-d 3.0. The scalable mode capability could be checked by reading
+	  /sys/devices/virtual/iommu/dmar*/intel-iommu/ecap. If this option
+	  is not selected, scalable mode support could also be enabled by
+	  passing intel_iommu=sm_on to the kernel. If not sure, please use
+	  the default value.
+
+config INTEL_IOMMU_PERF_EVENTS
+	bool "Intel IOMMU performance events"
+	default y
+	depends on INTEL_IOMMU && PERF_EVENTS
+	help
+	  Selecting this option will enable the performance monitoring
+	  infrastructure in the Intel IOMMU. It collects information about
+	  key events occurring during operation of the remapping hardware,
+	  to aid performance tuning and debug. These are available on modern
+	  processors which support Intel VT-d 4.0 and later.
+
+endif # INTEL_IOMMU