On Wed, Sep 10, 2014 at 9:51 AM, Toshi Kani <toshi.k...@hp.com> wrote:
> This patch changes reserve_memtype() to handle the WT cache mode.
> When PAT is not enabled, it continues to set UC- to *new_type for
> any non-WB request.
>
> When a target range is RAM, reserve_ram_pages_type() fails for WT
> for now. This function may not reserve a RAM range for WT since
> reserve_ram_pages_type() uses the page flags limited to three memory
> types, WB, WC and UC.
Should it fail if WT is unavailable due to errata? More generally,
how are all of the do_something_wc / do_something_wt /
do_something_nocache helpers supposed to handle unsupported types?
--Andy
>
> Signed-off-by: Toshi Kani <toshi.k...@hp.com>
> ---
> arch/x86/include/asm/cacheflush.h | 4 ++++
> arch/x86/mm/pat.c | 16 +++++++++++++---
> 2 files changed, 17 insertions(+), 3 deletions(-)
>
> diff --git a/arch/x86/include/asm/cacheflush.h
> b/arch/x86/include/asm/cacheflush.h
> index 157644b..c912680 100644
> --- a/arch/x86/include/asm/cacheflush.h
> +++ b/arch/x86/include/asm/cacheflush.h
> @@ -53,6 +53,10 @@ static inline void set_page_memtype(struct page *pg,
> case _PAGE_CACHE_MODE_WB:
> memtype_flags = _PGMT_WB;
> break;
> + case _PAGE_CACHE_MODE_WT:
> + case _PAGE_CACHE_MODE_WP:
> + pr_err("set_page_memtype: unsupported cachemode %d\n",
> memtype);
> + BUG();
> default:
> memtype_flags = _PGMT_DEFAULT;
> break;
> diff --git a/arch/x86/mm/pat.c b/arch/x86/mm/pat.c
> index 598d7c7..7644967 100644
> --- a/arch/x86/mm/pat.c
> +++ b/arch/x86/mm/pat.c
> @@ -268,6 +268,8 @@ static int pat_pagerange_is_ram(resource_size_t start,
> resource_size_t end)
>
> /*
> * For RAM pages, we use page flags to mark the pages with appropriate type.
> + * The page flags are currently limited to three types, WB, WC and UC. Hence,
> + * any request to WT or WP will fail with -EINVAL.
> * Here we do two pass:
> * - Find the memtype of all the pages in the range, look for any conflicts
> * - In case of no conflicts, set the new memtype for pages in the range
> @@ -279,6 +281,13 @@ static int reserve_ram_pages_type(u64 start, u64 end,
> struct page *page;
> u64 pfn;
>
> + if ((req_type == _PAGE_CACHE_MODE_WT) ||
> + (req_type == _PAGE_CACHE_MODE_WP)) {
> + if (new_type)
> + *new_type = _PAGE_CACHE_MODE_UC_MINUS;
> + return -EINVAL;
> + }
> +
> if (req_type == _PAGE_CACHE_MODE_UC) {
> /* We do not support strong UC */
> WARN_ON_ONCE(1);
> @@ -328,6 +337,7 @@ static int free_ram_pages_type(u64 start, u64 end)
> * - _PAGE_CACHE_MODE_WC
> * - _PAGE_CACHE_MODE_UC_MINUS
> * - _PAGE_CACHE_MODE_UC
> + * - _PAGE_CACHE_MODE_WT
> *
> * If new_type is NULL, function will return an error if it cannot reserve
> the
> * region with req_type. If new_type is non-NULL, function will return
> @@ -347,10 +357,10 @@ int reserve_memtype(u64 start, u64 end, enum
> page_cache_mode req_type,
> if (!pat_enabled) {
> /* This is identical to page table setting without PAT */
> if (new_type) {
> - if (req_type == _PAGE_CACHE_MODE_WC)
> - *new_type = _PAGE_CACHE_MODE_UC_MINUS;
> + if (req_type == _PAGE_CACHE_MODE_WB)
> + *new_type = _PAGE_CACHE_MODE_WB;
> else
> - *new_type = req_type;
> + *new_type = _PAGE_CACHE_MODE_UC_MINUS;
> }
> return 0;
> }
--
Andy Lutomirski
AMA Capital Management, LLC
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