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Subject[PATCH v11 4/12] x86, mm, pat: Change reserve_memtype() for WT
Date
From: Toshi Kani <toshi.kani@hp.com>

When a RAM range is requested to reserve_memtype(), it calls
reserve_ram_pages_type() to verify the requested type.
reserve_ram_pages_type() is changed to fail WT and WP requests
with -EINVAL since set_page_memtype() is limited to handle
three types, WB, WC and UC-.

Signed-off-by: Toshi Kani <toshi.kani@hp.com>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
---
Patch 10/12 enhances set_page_memtype() to support WT.
---
arch/x86/mm/pat.c | 10 ++++++++++
1 file changed, 10 insertions(+)

diff --git a/arch/x86/mm/pat.c b/arch/x86/mm/pat.c
index 3d9f125..85c9fcb 100644
--- a/arch/x86/mm/pat.c
+++ b/arch/x86/mm/pat.c
@@ -389,6 +389,8 @@ 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 limited to three types, WB, WC and UC-.
+ * WT and WP requests fail with -EINVAL, and UC gets redirected to UC-.
* 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
@@ -400,6 +402,13 @@ 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);
@@ -449,6 +458,7 @@ 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

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