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From: Toshi Kani <toshi.kani@hp.com>
To: akpm@linux-foundation.org, hpa@zytor.com, tglx@linutronix.de,
	mingo@redhat.com, arnd@arndb.de
Cc: linux-mm@kvack.org, x86@kernel.org, linux-kernel@vger.kernel.org,
	dave.hansen@intel.com, Elliott@hp.com,
	Toshi Kani <toshi.kani@hp.com>
Subject: [PATCH v3 6/6] x86, mm: Support huge KVA mappings on x86
Date: Tue,  3 Mar 2015 10:44:24 -0700	[thread overview]
Message-ID: <1425404664-19675-7-git-send-email-toshi.kani@hp.com> (raw)
In-Reply-To: <1425404664-19675-1-git-send-email-toshi.kani@hp.com>

This patch implements huge KVA mapping interfaces on x86.

On x86, MTRRs can override PAT memory types with a 4KB granularity.
When using a huge page, MTRRs can override the memory type of the
huge page, which may lead a performance penalty.  The processor
can also behave in an undefined manner if a huge page is mapped to
a memory range that MTRRs have mapped with multiple different memory
types.  Therefore, the mapping code falls back to use a smaller page
size toward 4KB when a mapping range is covered by non-WB type of
MTRRs.  The WB type of MTRRs has no affect on the PAT memory types.

pud_set_huge() and pmd_set_huge() call mtrr_type_lookup() to see
if a given range is covered by MTRRs.  MTRR_TYPE_WRBACK indicates
that the range is either covered by WB or not covered and the MTRR
default value is set to WB.  0xFF indicates that MTRRs are disabled.

HAVE_ARCH_HUGE_VMAP is selected when X86_64 or X86_32 with X86_PAE
is set.  X86_32 without X86_PAE is not supported since such config
can unlikey be benefited from this feature, and there was an issue
found in testing.

Signed-off-by: Toshi Kani <toshi.kani@hp.com>
---
 arch/x86/Kconfig      |    1 +
 arch/x86/mm/pgtable.c |   65 +++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 66 insertions(+)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index c2fb8a8..ef7d4a6 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -99,6 +99,7 @@ config X86
 	select IRQ_FORCED_THREADING
 	select HAVE_BPF_JIT if X86_64
 	select HAVE_ARCH_TRANSPARENT_HUGEPAGE
+	select HAVE_ARCH_HUGE_VMAP if X86_64 || (X86_32 && X86_PAE)
 	select ARCH_HAS_SG_CHAIN
 	select CLKEVT_I8253
 	select ARCH_HAVE_NMI_SAFE_CMPXCHG
diff --git a/arch/x86/mm/pgtable.c b/arch/x86/mm/pgtable.c
index 7b22ada..19c897e 100644
--- a/arch/x86/mm/pgtable.c
+++ b/arch/x86/mm/pgtable.c
@@ -4,6 +4,7 @@
 #include <asm/pgtable.h>
 #include <asm/tlb.h>
 #include <asm/fixmap.h>
+#include <asm/mtrr.h>
 
 #define PGALLOC_GFP GFP_KERNEL | __GFP_NOTRACK | __GFP_REPEAT | __GFP_ZERO
 
@@ -485,3 +486,67 @@ void native_set_fixmap(enum fixed_addresses idx, phys_addr_t phys,
 {
 	__native_set_fixmap(idx, pfn_pte(phys >> PAGE_SHIFT, flags));
 }
+
+#ifdef CONFIG_HAVE_ARCH_HUGE_VMAP
+int pud_set_huge(pud_t *pud, phys_addr_t addr, pgprot_t prot)
+{
+	u8 mtrr;
+
+	/*
+	 * Do not use a huge page when the range is covered by non-WB type
+	 * of MTRRs.
+	 */
+	mtrr = mtrr_type_lookup(addr, addr + PUD_SIZE);
+	if ((mtrr != MTRR_TYPE_WRBACK) && (mtrr != 0xFF))
+		return 0;
+
+	prot = pgprot_4k_2_large(prot);
+
+	set_pte((pte_t *)pud, pfn_pte(
+		(u64)addr >> PAGE_SHIFT,
+		__pgprot(pgprot_val(prot) | _PAGE_PSE)));
+
+	return 1;
+}
+
+int pmd_set_huge(pmd_t *pmd, phys_addr_t addr, pgprot_t prot)
+{
+	u8 mtrr;
+
+	/*
+	 * Do not use a huge page when the range is covered by non-WB type
+	 * of MTRRs.
+	 */
+	mtrr = mtrr_type_lookup(addr, addr + PMD_SIZE);
+	if ((mtrr != MTRR_TYPE_WRBACK) && (mtrr != 0xFF))
+		return 0;
+
+	prot = pgprot_4k_2_large(prot);
+
+	set_pte((pte_t *)pmd, pfn_pte(
+		(u64)addr >> PAGE_SHIFT,
+		__pgprot(pgprot_val(prot) | _PAGE_PSE)));
+
+	return 1;
+}
+
+int pud_clear_huge(pud_t *pud)
+{
+	if (pud_large(*pud)) {
+		pud_clear(pud);
+		return 1;
+	}
+
+	return 0;
+}
+
+int pmd_clear_huge(pmd_t *pmd)
+{
+	if (pmd_large(*pmd)) {
+		pmd_clear(pmd);
+		return 1;
+	}
+
+	return 0;
+}
+#endif	/* CONFIG_HAVE_ARCH_HUGE_VMAP */

  parent reply	other threads:[~2015-03-03 17:45 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-03-03 17:44 [PATCH v3 0/6] Kernel huge I/O mapping support Toshi Kani
2015-03-03 17:44 ` [PATCH v3 1/6] mm: Change __get_vm_area_node() to use fls_long() Toshi Kani
2015-03-03 17:44 ` [PATCH v3 2/6] lib: Add huge I/O map capability interfaces Toshi Kani
2015-03-03 17:44 ` [PATCH v3 3/6] mm: Change ioremap to set up huge I/O mappings Toshi Kani
2015-03-04 22:09   ` Ingo Molnar
2015-03-04 23:15     ` Toshi Kani
2015-03-03 17:44 ` [PATCH v3 4/6] mm: Change vunmap to tear down huge KVA mappings Toshi Kani
2015-03-03 17:44 ` [PATCH v3 5/6] x86, mm: Support huge I/O mapping capability I/F Toshi Kani
2015-03-03 17:44 ` Toshi Kani [this message]
2015-03-03 22:44   ` [PATCH v3 6/6] x86, mm: Support huge KVA mappings on x86 Andrew Morton
2015-03-03 23:14     ` Toshi Kani
2015-03-04  1:00       ` Andrew Morton
2015-03-04 16:23         ` Toshi Kani
2015-03-04 20:17           ` Ingo Molnar
2015-03-04 21:16             ` Toshi Kani

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