Re: [PATCHv4 14/14] x86/acpi: Add support for CPU offlining for ACPI MADT wakeup method

[Huang, Kai]

> +
> +static void acpi_mp_stop_other_cpus(int wait)
> +{
> +	smp_shutdown_nonboot_cpus(smp_processor_id());
> +}

Is this and ...

+	smp_ops.stop_other_cpus = acpi_mp_stop_other_cpus;

... this below still needed?

I think the current native_stop_other_cpus() should just work given you have set
up ...

+	smp_ops.crash_play_dead = crash_acpi_mp_play_dead;

... for TDX guest?

> +
> +/* The argument is required to match type of x86_mapping_info::alloc_pgt_page */
> +static void __init *alloc_pgt_page(void *dummy)
> +{
> +	return memblock_alloc(PAGE_SIZE, PAGE_SIZE);
> +}
> +
> +/*
> + * Make sure asm_acpi_mp_play_dead() is present in the identity mapping at
> + * the same place as in the kernel page tables. asm_acpi_mp_play_dead() switches
> + * to the identity mapping and the function has be present at the same spot in
> + * the virtual address space before and after switching page tables.
> + */
> +static int __init init_transition_pgtable(pgd_t *pgd)
> +{
> +	pgprot_t prot = PAGE_KERNEL_EXEC_NOENC;
> +	unsigned long vaddr, paddr;
> +	p4d_t *p4d;
> +	pud_t *pud;
> +	pmd_t *pmd;
> +	pte_t *pte;
> +
> +	vaddr = (unsigned long)asm_acpi_mp_play_dead;
> +	pgd += pgd_index(vaddr);
> +	if (!pgd_present(*pgd)) {
> +		p4d = (p4d_t *)alloc_pgt_page(NULL);
> +		if (!p4d)
> +			return -ENOMEM;
> +		set_pgd(pgd, __pgd(__pa(p4d) | _KERNPG_TABLE));
> +	}
> +	p4d = p4d_offset(pgd, vaddr);
> +	if (!p4d_present(*p4d)) {
> +		pud = (pud_t *)alloc_pgt_page(NULL);
> +		if (!pud)
> +			return -ENOMEM;
> +		set_p4d(p4d, __p4d(__pa(pud) | _KERNPG_TABLE));
> +	}
> +	pud = pud_offset(p4d, vaddr);
> +	if (!pud_present(*pud)) {
> +		pmd = (pmd_t *)alloc_pgt_page(NULL);
> +		if (!pmd)
> +			return -ENOMEM;
> +		set_pud(pud, __pud(__pa(pmd) | _KERNPG_TABLE));
> +	}
> +	pmd = pmd_offset(pud, vaddr);
> +	if (!pmd_present(*pmd)) {
> +		pte = (pte_t *)alloc_pgt_page(NULL);
> +		if (!pte)
> +			return -ENOMEM;
> +		set_pmd(pmd, __pmd(__pa(pte) | _KERNPG_TABLE));
> +	}
> +	pte = pte_offset_kernel(pmd, vaddr);
> +
> +	paddr = __pa(vaddr);
> +	set_pte(pte, pfn_pte(paddr >> PAGE_SHIFT, prot));
> +
> +	return 0;
> +}

Sorry for saying this late.  I think we can also use kernel_ident_mapping_init()
to do the init_transition_pgtable()?  We can set struct x86_mapping_info::offset
to __PAGE_OFFSET to do that?

Looks set_up_temporary_mappings() in arch/x86/power/hibernate_64.c uses the same
trick.

Anyway I am not sure how many LoC (assuming can do) can be saved so up to you.

> +
> +static void __init free_pte(pmd_t *pmd)
> +{
> +	pte_t *pte = pte_offset_kernel(pmd, 0);
> +
> +	memblock_free(pte, PAGE_SIZE);
> +}
> +
> +static void __init free_pmd(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(&pmd[i]);
> +	}
> +
> +	memblock_free(pmd, PAGE_SIZE);
> +}
> +
> +static void __init free_pud(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(&pud[i]);
> +	}
> +
> +	memblock_free(pud, PAGE_SIZE);
> +}
> +
> +static void __init free_p4d(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(&p4d[i]);
> +	}
> +
> +	if (pgtable_l5_enabled())
> +		memblock_free(p4d, PAGE_SIZE);
> +}
> +
> +static void __init free_pgd(pgd_t *pgd)
> +{
> +	int i;
> +
> +	for (i = 0; i < PTRS_PER_PGD; i++) {
> +		if (!pgd_present(pgd[i]))
> +			continue;
> +
> +		free_p4d(&pgd[i]);
> +	}
> +
> +	memblock_free(pgd, PAGE_SIZE);
> +}

It's a little bit sad such cleanup code isn't in common code, e.g., with a 

	void (*free_pgt_page)(void *);

to allow the user to specify how to free the page table.

But this can be future job if needed.


[...]

>  int __init acpi_parse_mp_wake(union acpi_subtable_headers *header,
>  			      const unsigned long end)
>  {
>  	struct acpi_madt_multiproc_wakeup *mp_wake;
>  
>  	mp_wake = (struct acpi_madt_multiproc_wakeup *)header;
> -	if (BAD_MADT_ENTRY(mp_wake, end))
> +
> +        /*
> +         * Cannot use the standard BAD_MADT_ENTRY() to sanity check the @mp_wake
> +         * entry.  'sizeof (struct acpi_madt_multiproc_wakeup)' can be larger
> +         * than the actual size of the MP wakeup entry in ACPI table because the
> +	 * 'reset_vector' is only available in the V1 MP wakeup structure.
> +         */

Space/tab issue.

> +	if (!mp_wake)
> +		return -EINVAL;
> +	if (end - (unsigned long)mp_wake < ACPI_MADT_MP_WAKEUP_SIZE_V0)
> +		return -EINVAL;
> +	if (mp_wake->header.length < ACPI_MADT_MP_WAKEUP_SIZE_V0)
>  		return -EINVAL;
>