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, 131 insertions, 0 deletions

diff --git a/include/asm-generic/hugetlb.h b/include/asm-generic/hugetlb.h
new file mode 100644
index 000000000..635c41cc3
--- /dev/null
+++ b/include/asm-generic/hugetlb.h
@@ -0,0 +1,131 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _ASM_GENERIC_HUGETLB_H
+#define _ASM_GENERIC_HUGETLB_H
+
+#include <linux/swap.h>
+#include <linux/swapops.h>
+
+static inline unsigned long huge_pte_write(pte_t pte)
+{
+	return pte_write(pte);
+}
+
+static inline unsigned long huge_pte_dirty(pte_t pte)
+{
+	return pte_dirty(pte);
+}
+
+static inline pte_t huge_pte_mkwrite(pte_t pte)
+{
+	return pte_mkwrite_novma(pte);
+}
+
+#ifndef __HAVE_ARCH_HUGE_PTE_WRPROTECT
+static inline pte_t huge_pte_wrprotect(pte_t pte)
+{
+	return pte_wrprotect(pte);
+}
+#endif
+
+static inline pte_t huge_pte_mkdirty(pte_t pte)
+{
+	return pte_mkdirty(pte);
+}
+
+static inline pte_t huge_pte_modify(pte_t pte, pgprot_t newprot)
+{
+	return pte_modify(pte, newprot);
+}
+
+#ifndef __HAVE_ARCH_HUGE_PTE_MKUFFD
+static inline pte_t huge_pte_mkuffd(pte_t pte)
+{
+	return huge_pte_wrprotect(pte_mkuffd(pte));
+}
+#endif
+
+#ifndef __HAVE_ARCH_HUGE_PTE_CLEAR_UFFD
+static inline pte_t huge_pte_clear_uffd(pte_t pte)
+{
+	return pte_clear_uffd(pte);
+}
+#endif
+
+#ifndef __HAVE_ARCH_HUGE_PTE_UFFD
+static inline int huge_pte_uffd(pte_t pte)
+{
+	return pte_uffd(pte);
+}
+#endif
+
+#ifndef __HAVE_ARCH_HUGE_PTE_CLEAR
+static inline void huge_pte_clear(struct mm_struct *mm, unsigned long addr,
+		    pte_t *ptep, unsigned long sz)
+{
+	pte_clear(mm, addr, ptep);
+}
+#endif
+
+#ifndef __HAVE_ARCH_HUGE_SET_HUGE_PTE_AT
+static inline void set_huge_pte_at(struct mm_struct *mm, unsigned long addr,
+		pte_t *ptep, pte_t pte, unsigned long sz)
+{
+	set_pte_at(mm, addr, ptep, pte);
+}
+#endif
+
+#ifndef __HAVE_ARCH_HUGE_PTEP_GET_AND_CLEAR
+static inline pte_t huge_ptep_get_and_clear(struct mm_struct *mm,
+		unsigned long addr, pte_t *ptep, unsigned long sz)
+{
+	return ptep_get_and_clear(mm, addr, ptep);
+}
+#endif
+
+#ifndef __HAVE_ARCH_HUGE_PTEP_CLEAR_FLUSH
+static inline pte_t huge_ptep_clear_flush(struct vm_area_struct *vma,
+		unsigned long addr, pte_t *ptep)
+{
+	return ptep_clear_flush(vma, addr, ptep);
+}
+#endif
+
+#ifndef __HAVE_ARCH_HUGE_PTE_NONE
+static inline int huge_pte_none(pte_t pte)
+{
+	return pte_none(pte);
+}
+#endif
+
+#ifndef __HAVE_ARCH_HUGE_PTEP_SET_WRPROTECT
+static inline void huge_ptep_set_wrprotect(struct mm_struct *mm,
+		unsigned long addr, pte_t *ptep)
+{
+	ptep_set_wrprotect(mm, addr, ptep);
+}
+#endif
+
+#ifndef __HAVE_ARCH_HUGE_PTEP_SET_ACCESS_FLAGS
+static inline int huge_ptep_set_access_flags(struct vm_area_struct *vma,
+		unsigned long addr, pte_t *ptep,
+		pte_t pte, int dirty)
+{
+	return ptep_set_access_flags(vma, addr, ptep, pte, dirty);
+}
+#endif
+
+#ifndef __HAVE_ARCH_HUGE_PTEP_GET
+static inline pte_t huge_ptep_get(struct mm_struct *mm, unsigned long addr, pte_t *ptep)
+{
+	return ptep_get(ptep);
+}
+#endif
+
+#ifndef __HAVE_ARCH_GIGANTIC_PAGE_RUNTIME_SUPPORTED
+static inline bool gigantic_page_runtime_supported(void)
+{
+	return IS_ENABLED(CONFIG_ARCH_HAS_GIGANTIC_PAGE);
+}
+#endif /* __HAVE_ARCH_GIGANTIC_PAGE_RUNTIME_SUPPORTED */
+
+#endif /* _ASM_GENERIC_HUGETLB_H */