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, 52 insertions, 0 deletions

diff --git a/tools/scripts/Makefile.arch b/tools/scripts/Makefile.arch
new file mode 100644
index 000000000..ed5f008d4
--- /dev/null
+++ b/tools/scripts/Makefile.arch
@@ -0,0 +1,52 @@
+# SPDX-License-Identifier: GPL-2.0
+HOSTARCH := $(shell uname -m | sed -e s/i.86/x86/ -e s/x86_64/x86/ \
+                                  -e s/sun4u/sparc/ -e s/sparc64/sparc/ \
+                                  -e /arm64/!s/arm.*/arm/ -e s/sa110/arm/ \
+                                  -e s/s390x/s390/ -e s/parisc64/parisc/ \
+                                  -e s/ppc.*/powerpc/ -e s/mips.*/mips/ \
+                                  -e s/sh[234].*/sh/ -e s/aarch64.*/arm64/ \
+                                  -e s/riscv.*/riscv/ -e s/loongarch.*/loongarch/)
+
+ifeq ($(strip $(ARCH)),)
+override ARCH := $(HOSTARCH)
+endif
+
+SRCARCH := $(ARCH)
+
+# Additional ARCH settings for x86
+ifeq ($(ARCH),i386)
+        SRCARCH := x86
+endif
+ifeq ($(ARCH),x86_64)
+        SRCARCH := x86
+endif
+
+# Additional ARCH settings for sparc
+ifeq ($(ARCH),sparc32)
+       SRCARCH := sparc
+endif
+ifeq ($(ARCH),sparc64)
+       SRCARCH := sparc
+endif
+
+# Additional ARCH settings for loongarch
+ifeq ($(ARCH),loongarch32)
+       SRCARCH := loongarch
+endif
+
+ifeq ($(ARCH),loongarch64)
+       SRCARCH := loongarch
+endif
+
+# Probe for __LP64__ only when the compiler is installed: this runs at
+# parse time for every target, including ones that never compile, e.g.
+# install-build-deps, and would otherwise spew "gcc: not found" when the
+# compiler is not yet installed. Only the first word of CC is consulted,
+# as CC may carry arguments, e.g. 'ccache gcc'. When the guard fails it
+# prints nothing, leaving LP64 unset, as if the probe had failed.
+LP64 := $(shell if command -v $(firstword ${CC}) >/dev/null 2>&1; then echo __LP64__ | ${CC} ${CFLAGS} -E -x c -; fi | tail -n 1)
+ifeq ($(LP64), 1)
+  IS_64_BIT := 1
+else
+  IS_64_BIT := 0
+endif