Messages in this thread Patch in this message | | | From | Borislav Petkov <> | Subject | [PATCH -v3 1/3] x86, AMD: Correct F15h IC aliasing issue | Date | Thu, 4 Aug 2011 16:58:36 +0200 |
| |
From: Borislav Petkov <borislav.petkov@amd.com>
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 setting 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> --- Documentation/kernel-parameters.txt | 13 ++++++ arch/x86/include/asm/elf.h | 27 ++++++++++++ arch/x86/kernel/cpu/amd.c | 10 ++++ arch/x86/kernel/sys_x86_64.c | 79 +++++++++++++++++++++++++++++++++- arch/x86/mm/mmap.c | 15 ------- arch/x86/vdso/vma.c | 9 ++++ 6 files changed, 135 insertions(+), 18 deletions(-)
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt index aa47be7..af73c03 100644 --- a/Documentation/kernel-parameters.txt +++ b/Documentation/kernel-parameters.txt @@ -299,6 +299,19 @@ bytes respectively. Such letter suffixes can also be entirely omitted. behaviour to be specified. Bit 0 enables warnings, bit 1 enables fixups, and bit 2 sends a segfault. + align_va_addr= [X86-64] + Align virtual addresses by clearing slice [14:12] when + allocating a VMA at process creation time. This option + gives you up to 3% performance improvement on AMD F15h + machines (where it is enabled by default) for a + CPU-intensive style benchmark, and it can vary highly in + a microbenchmark depending on workload and compiler. + + 1: only for 32-bit processes + 2: only for 64-bit processes + on: enable for both 32- and 64-bit processes + off: disable for both 32- and 64-bit processes + amd_iommu= [HW,X86-84] Pass parameters to the AMD IOMMU driver in the system. Possible values are: diff --git a/arch/x86/include/asm/elf.h b/arch/x86/include/asm/elf.h index f2ad216..50e9070 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 +321,30 @@ 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), +}; + +extern int align_va_addr; +extern unsigned long align_upperbit; +extern unsigned long align_addr(unsigned long, struct file *, enum align_flags); #endif /* _ASM_X86_ELF_H */ diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c index b13ed39..5a48cac 100644 --- a/arch/x86/kernel/cpu/amd.c +++ b/arch/x86/kernel/cpu/amd.c @@ -458,6 +458,16 @@ static void __cpuinit early_init_amd(struct cpuinfo_x86 *c) "with P0 frequency!\n"); } } + + if (c->x86 == 0x15) { + u32 cpuid, assoc; + + cpuid = cpuid_edx(0x80000005); + assoc = cpuid >> 16 & 0xff; + + align_upperbit = ((cpuid >> 24) << 10) / assoc; + align_va_addr = ALIGN_VA_32 | ALIGN_VA_64; + } } static void __cpuinit init_amd(struct cpuinfo_x86 *c) diff --git a/arch/x86/kernel/sys_x86_64.c b/arch/x86/kernel/sys_x86_64.c index ff14a50..b9e45f2 100644 --- a/arch/x86/kernel/sys_x86_64.c +++ b/arch/x86/kernel/sys_x86_64.c @@ -18,6 +18,70 @@ #include <asm/ia32.h> #include <asm/syscalls.h> +/* see Documentation/kernel-parameters.txt */ +int __read_mostly align_va_addr = -1; +unsigned long align_upperbit; + +/* + * Align a virtual address to avoid aliasing in the I$ on AMD F15h. + * + * @flags denotes the allocation direction - bottomup or topdown - + * or vDSO; see call sites below. + */ +unsigned long align_addr(unsigned long addr, struct file *filp, + enum align_flags flags) +{ + unsigned long tmp_addr; + + /* handle 32- and 64-bit case with a single conditional */ + if (align_va_addr < 0 || !(align_va_addr & (2 - mmap_is_ia32()))) + return addr; + + if (!(current->flags & PF_RANDOMIZE)) + return addr; + + if (!((flags & ALIGN_VDSO) || filp)) + return addr; + + tmp_addr = addr | ((align_upperbit - 1) & PAGE_MASK); + + /* + * We need an address which is <= than the original + * one when in topdown direction. + */ + if ((tmp_addr > addr) && (flags & ALIGN_TOPDOWN)) + tmp_addr -= align_upperbit; + + return tmp_addr; +} + +static int __init control_va_addr_alignment(char *str) +{ + /* guard against enabling this on other CPU families */ + if (align_va_addr < 0) + return 1; + + if (*str == 0) + return 1; + + if (*str == '=') + str++; + + if (!strcmp(str, "32")) + align_va_addr = ALIGN_VA_32; + else if (!strcmp(str, "64")) + align_va_addr = ALIGN_VA_64; + else if (!strcmp(str, "off")) + align_va_addr = 0; + else if (!strcmp(str, "on")) + align_va_addr = ALIGN_VA_32 | ALIGN_VA_64; + else + return 0; + + return 1; +} +__setup("align_va_addr", control_va_addr_alignment); + SYSCALL_DEFINE6(mmap, unsigned long, addr, unsigned long, len, unsigned long, prot, unsigned long, flags, unsigned long, fd, unsigned long, off) @@ -92,6 +156,9 @@ arch_get_unmapped_area(struct file *filp, unsigned long addr, start_addr = addr; full_search: + + addr = align_addr(addr, filp, 0); + for (vma = find_vma(mm, addr); ; vma = vma->vm_next) { /* At this point: (!vma || addr < vma->vm_end). */ if (end - len < addr) { @@ -117,6 +184,7 @@ full_search: mm->cached_hole_size = vma->vm_start - addr; addr = vma->vm_end; + addr = align_addr(addr, filp, 0); } } @@ -161,10 +229,13 @@ arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0, /* make sure it can fit in the remaining address space */ if (addr > len) { - vma = find_vma(mm, addr-len); - if (!vma || addr <= vma->vm_start) + unsigned long tmp_addr = align_addr(addr - len, filp, + ALIGN_TOPDOWN); + + vma = find_vma(mm, tmp_addr); + if (!vma || tmp_addr + len <= vma->vm_start) /* remember the address as a hint for next time */ - return mm->free_area_cache = addr-len; + return mm->free_area_cache = tmp_addr; } if (mm->mmap_base < len) @@ -173,6 +244,8 @@ arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0, addr = mm->mmap_base-len; do { + addr = align_addr(addr, filp, ALIGN_TOPDOWN); + /* * Lookup failure means no vma is above this address, * else if new region fits below vma->vm_start, diff --git a/arch/x86/mm/mmap.c b/arch/x86/mm/mmap.c index 1dab519..d4c0736 100644 --- a/arch/x86/mm/mmap.c +++ b/arch/x86/mm/mmap.c @@ -51,21 +51,6 @@ static unsigned int stack_maxrandom_size(void) #define MIN_GAP (128*1024*1024UL + stack_maxrandom_size()) #define MAX_GAP (TASK_SIZE/6*5) -/* - * True on X86_32 or when emulating IA32 on X86_64 - */ -static 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; -} - static int mmap_is_legacy(void) { if (current->personality & ADDR_COMPAT_LAYOUT) diff --git a/arch/x86/vdso/vma.c b/arch/x86/vdso/vma.c index 7abd2be..caa42ce 100644 --- a/arch/x86/vdso/vma.c +++ b/arch/x86/vdso/vma.c @@ -69,6 +69,15 @@ static unsigned long vdso_addr(unsigned long start, unsigned len) addr = start + (offset << PAGE_SHIFT); if (addr >= end) addr = end; + + /* + * page-align it here so that get_unmapped_area doesn't + * align it wrongfully again to the next page. addr can come in 4K + * unaligned here as a result of stack start randomization. + */ + addr = PAGE_ALIGN(addr); + addr = align_addr(addr, NULL, ALIGN_VDSO); + return addr; } -- 1.7.4.rc2
| |