x86, amd: Avoid cache aliasing penalties on AMD family 15h

This patch provides performance tuning for the "Bulldozer" CPU. With its
shared instruction cache there is a chance of generating an excessive
number of cache cross-invalidates when running specific workloads on the
cores of a compute module.

This excessive amount of cross-invalidations can be observed if cache
lines backed by shared physical memory alias in bits [14:12] of their
virtual addresses, as those bits are used for the index generation.

This patch addresses the issue by clearing all the bits in the [14:12]
slice of the file mapping's virtual address at generation time, thus
forcing those bits the same for all mappings of a single shared library
across processes and, in doing so, avoids instruction cache aliases.

It also adds the command line option "align_va_addr=(32|64|on|off)" with
which virtual address alignment can be enabled for 32-bit or 64-bit x86
individually, or both, or be completely disabled.

This change leaves virtual region address allocation on other families
and/or vendors unaffected.

Signed-off-by: Borislav Petkov <borislav.petkov@amd.com>
Link: http://lkml.kernel.org/r/1312550110-24160-2-git-send-email-bp@amd64.org
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>

1 files changed, 31 insertions, 0 deletions

diff --git a/arch/x86/include/asm/elf.h b/arch/x86/include/asm/elf.h
index f2ad216..5f962df 100644
--- a/arch/x86/include/asm/elf.h
+++ b/arch/x86/include/asm/elf.h
@@ -4,6 +4,7 @@
 /*
  * ELF register definitions..
  */
+#include <linux/thread_info.h>
 
 #include <asm/ptrace.h>
 #include <asm/user.h>
@@ -320,4 +321,34 @@ extern int syscall32_setup_pages(struct linux_binprm *, int exstack);
 extern unsigned long arch_randomize_brk(struct mm_struct *mm);
 #define arch_randomize_brk arch_randomize_brk
 
+/*
+ * True on X86_32 or when emulating IA32 on X86_64
+ */
+static inline int mmap_is_ia32(void)
+{
+#ifdef CONFIG_X86_32
+	return 1;
+#endif
+#ifdef CONFIG_IA32_EMULATION
+	if (test_thread_flag(TIF_IA32))
+		return 1;
+#endif
+	return 0;
+}
+
+/* The first two values are special, do not change. See align_addr() */
+enum align_flags {
+	ALIGN_VA_32	= BIT(0),
+	ALIGN_VA_64	= BIT(1),
+	ALIGN_VDSO	= BIT(2),
+	ALIGN_TOPDOWN	= BIT(3),
+};
+
+struct va_alignment {
+	int flags;
+	unsigned long mask;
+} ____cacheline_aligned;
+
+extern struct va_alignment va_align;
+extern unsigned long align_addr(unsigned long, struct file *, enum align_flags);
 #endif /* _ASM_X86_ELF_H */