On Wed, 2024-01-24 at 14:55 +0200, Kirill A. Shutemov wrote:
> The helper complements kernel_ident_mapping_init(): it frees the
> identity mapping that was previously allocated. It will be used in the
> error path to free a partially allocated mapping or if the mapping is no
> longer needed.
>
> The caller provides a struct x86_mapping_info with the free_pgd_page()
> callback hooked up and the pgd_t to free.
>
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
FWIW:
Acked-by: Kai Huang <kai.huang@xxxxxxxxx>
> ---
> arch/x86/include/asm/init.h | 3 ++
> arch/x86/mm/ident_map.c | 73 +++++++++++++++++++++++++++++++++++++
> 2 files changed, 76 insertions(+)
>
> diff --git a/arch/x86/include/asm/init.h b/arch/x86/include/asm/init.h
> index cc9ccf61b6bd..14d72727d7ee 100644
> --- a/arch/x86/include/asm/init.h
> +++ b/arch/x86/include/asm/init.h
> @@ -6,6 +6,7 @@
>
> struct x86_mapping_info {
> void *(*alloc_pgt_page)(void *); /* allocate buf for page table */
> + void (*free_pgt_page)(void *, void *); /* free buf for page table */
> void *context; /* context for alloc_pgt_page */
> unsigned long page_flag; /* page flag for PMD or PUD entry */
> unsigned long offset; /* ident mapping offset */
> @@ -16,4 +17,6 @@ struct x86_mapping_info {
> int kernel_ident_mapping_init(struct x86_mapping_info *info, pgd_t *pgd_page,
> unsigned long pstart, unsigned long pend);
>
> +void kernel_ident_mapping_free(struct x86_mapping_info *info, pgd_t *pgd);
> +
> #endif /* _ASM_X86_INIT_H */
> diff --git a/arch/x86/mm/ident_map.c b/arch/x86/mm/ident_map.c
> index 968d7005f4a7..3996af7b4abf 100644
> --- a/arch/x86/mm/ident_map.c
> +++ b/arch/x86/mm/ident_map.c
> @@ -4,6 +4,79 @@
> * included by both the compressed kernel and the regular kernel.
> */
>
> +static void free_pte(struct x86_mapping_info *info, pmd_t *pmd)
> +{
> + pte_t *pte = pte_offset_kernel(pmd, 0);
> +
> + info->free_pgt_page(pte, info->context);
> +}
> +
> +static void free_pmd(struct x86_mapping_info *info, pud_t *pud)
> +{
> + pmd_t *pmd = pmd_offset(pud, 0);
> + int i;
> +
> + for (i = 0; i < PTRS_PER_PMD; i++) {
> + if (!pmd_present(pmd[i]))
> + continue;
> +
> + if (pmd_leaf(pmd[i]))
> + continue;
> +
> + free_pte(info, &pmd[i]);
> + }
> +
> + info->free_pgt_page(pmd, info->context);
> +}
> +
> +static void free_pud(struct x86_mapping_info *info, p4d_t *p4d)
> +{
> + pud_t *pud = pud_offset(p4d, 0);
> + int i;
> +
> + for (i = 0; i < PTRS_PER_PUD; i++) {
> + if (!pud_present(pud[i]))
> + continue;
> +
> + if (pud_leaf(pud[i]))
> + continue;
> +
> + free_pmd(info, &pud[i]);
> + }
> +
> + info->free_pgt_page(pud, info->context);
> +}
> +
> +static void free_p4d(struct x86_mapping_info *info, pgd_t *pgd)
> +{
> + p4d_t *p4d = p4d_offset(pgd, 0);
> + int i;
> +
> + for (i = 0; i < PTRS_PER_P4D; i++) {
> + if (!p4d_present(p4d[i]))
> + continue;
> +
> + free_pud(info, &p4d[i]);
> + }
> +
> + if (pgtable_l5_enabled())
> + info->free_pgt_page(pgd, info->context);
> +}
> +
> +void kernel_ident_mapping_free(struct x86_mapping_info *info, pgd_t *pgd)
> +{
> + int i;
> +
> + for (i = 0; i < PTRS_PER_PGD; i++) {
> + if (!pgd_present(pgd[i]))
> + continue;
> +
> + free_p4d(info, &pgd[i]);
> + }
> +
> + info->free_pgt_page(pgd, info->context);
> +}
> +
> static void ident_pmd_init(struct x86_mapping_info *info, pmd_t *pmd_page,
> unsigned long addr, unsigned long end)
> {
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