On Mon, 26 Jan 2015 16:13:24 -0700 Toshi Kani <toshi.kani@xxxxxx> wrote:
> Add ioremap_pud_enabled() and ioremap_pmd_enabled(), which
> return 1 when I/O mappings of pud/pmd are enabled on the kernel.
>
> ioremap_huge_init() calls arch_ioremap_pud_supported() and
> arch_ioremap_pmd_supported() to initialize the capabilities.
>
> A new kernel option "nohgiomap" is also added, so that user can
> disable the huge I/O map capabilities if necessary.
Why? What's the problem with leaving it enabled?
> --- a/Documentation/kernel-parameters.txt
> +++ b/Documentation/kernel-parameters.txt
> @@ -2304,6 +2304,8 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
> register save and restore. The kernel will only save
> legacy floating-point registers on task switch.
>
> + nohgiomap [KNL,x86] Disable huge I/O mappings.
That reads like "no high iomap" to me. "nohugeiomap" would be better.
> --- a/lib/ioremap.c
> +++ b/lib/ioremap.c
> @@ -13,6 +13,44 @@
> #include <asm/cacheflush.h>
> #include <asm/pgtable.h>
>
> +#ifdef CONFIG_HUGE_IOMAP
> +int __read_mostly ioremap_pud_capable;
> +int __read_mostly ioremap_pmd_capable;
> +int __read_mostly ioremap_huge_disabled;
> +
> +static int __init set_nohgiomap(char *str)
> +{
> + ioremap_huge_disabled = 1;
> + return 0;
> +}
> +early_param("nohgiomap", set_nohgiomap);
Why early?
> +static inline void ioremap_huge_init(void)
> +{
> + if (!ioremap_huge_disabled) {
> + if (arch_ioremap_pud_supported())
> + ioremap_pud_capable = 1;
> + if (arch_ioremap_pmd_supported())
> + ioremap_pmd_capable = 1;
> + }
> +}
> +
> +static inline int ioremap_pud_enabled(void)
> +{
> + return ioremap_pud_capable;
> +}
> +
> +static inline int ioremap_pmd_enabled(void)
> +{
> + return ioremap_pmd_capable;
> +}
> +
> +#else /* !CONFIG_HUGE_IOMAP */
> +static inline void ioremap_huge_init(void) { }
> +static inline int ioremap_pud_enabled(void) { return 0; }
> +static inline int ioremap_pmd_enabled(void) { return 0; }
> +#endif /* CONFIG_HUGE_IOMAP */
> +
> static int ioremap_pte_range(pmd_t *pmd, unsigned long addr,
> unsigned long end, phys_addr_t phys_addr, pgprot_t prot)
> {
> @@ -74,6 +112,12 @@ int ioremap_page_range(unsigned long addr,
> unsigned long start;
> unsigned long next;
> int err;
> + static int ioremap_huge_init_done;
> +
> + if (!ioremap_huge_init_done) {
> + ioremap_huge_init_done = 1;
> + ioremap_huge_init();
> + }
Looks hacky. Why can't we just get the startup ordering correct? It
at least needs a comment which fully explains the situation.
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