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, 42 insertions, 0 deletions

diff --git a/include/asm-generic/msi.h b/include/asm-generic/msi.h
new file mode 100644
index 000000000..92cca4b23
--- /dev/null
+++ b/include/asm-generic/msi.h
@@ -0,0 +1,42 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __ASM_GENERIC_MSI_H
+#define __ASM_GENERIC_MSI_H
+
+#include <linux/types.h>
+
+#ifdef CONFIG_GENERIC_MSI_IRQ
+
+#ifndef NUM_MSI_ALLOC_SCRATCHPAD_REGS
+# define NUM_MSI_ALLOC_SCRATCHPAD_REGS	2
+#endif
+
+struct msi_desc;
+
+/**
+ * struct msi_alloc_info - Default structure for MSI interrupt allocation.
+ * @desc:	Pointer to msi descriptor
+ * @hwirq:	Associated hw interrupt number in the domain
+ * @scratchpad:	Storage for implementation specific scratch data
+ *
+ * Architectures can provide their own implementation by not including
+ * asm-generic/msi.h into their arch specific header file.
+ */
+typedef struct msi_alloc_info {
+	struct msi_desc			*desc;
+	irq_hw_number_t			hwirq;
+	unsigned long			flags;
+	union {
+		unsigned long		ul;
+		void			*ptr;
+	} scratchpad[NUM_MSI_ALLOC_SCRATCHPAD_REGS];
+} msi_alloc_info_t;
+
+/* Device generating MSIs is proxying for another device */
+#define MSI_ALLOC_FLAGS_PROXY_DEVICE	(1UL << 0)
+#define MSI_ALLOC_FLAGS_FIXED_MSG_DATA	(1UL << 1)
+
+#define GENERIC_MSI_DOMAIN_OPS		1
+
+#endif /* CONFIG_GENERIC_MSI_IRQ */
+
+#endif