From 7a0fc404ae663776e96db43879a0fa24fec1fa3a Mon Sep 17 00:00:00 2001 From: "H. Peter Anvin" Date: Tue, 13 Apr 2010 14:40:54 -0700 Subject: [PATCH] x86: Disable large pages on CPUs with Atom erratum AAE44 Atom erratum AAE44/AAF40/AAG38/AAH41: "If software clears the PS (page size) bit in a present PDE (page directory entry), that will cause linear addresses mapped through this PDE to use 4-KByte pages instead of using a large page after old TLB entries are invalidated. Due to this erratum, if a code fetch uses this PDE before the TLB entry for the large page is invalidated then it may fetch from a different physical address than specified by either the old large page translation or the new 4-KByte page translation. This erratum may also cause speculative code fetches from incorrect addresses." [http://download.intel.com/design/processor/specupdt/319536.pdf] Where as commit 211b3d03c7400f48a781977a50104c9d12f4e229 seems to workaround errata AAH41 (mixed 4K TLBs) it reduces the window of opportunity for the bug to occur and does not totally remove it. This patch disables mixed 4K/4MB page tables totally avoiding the page splitting and not tripping this processor issue. This is based on an original patch by Colin King. Originally-by: Colin Ian King Cc: Colin Ian King Cc: Ingo Molnar Signed-off-by: H. Peter Anvin LKML-Reference: <1269271251-19775-1-git-send-email-colin.king@canonical.com> Cc: --- arch/x86/kernel/cpu/intel.c | 21 +++++++++++++++++++++ 1 file changed, 21 insertions(+) diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c index 7e1cca13af35..1366c7cfd483 100644 --- a/arch/x86/kernel/cpu/intel.c +++ b/arch/x86/kernel/cpu/intel.c @@ -47,6 +47,27 @@ static void __cpuinit early_init_intel(struct cpuinfo_x86 *c) (c->x86 == 0x6 && c->x86_model >= 0x0e)) set_cpu_cap(c, X86_FEATURE_CONSTANT_TSC); + /* + * Atom erratum AAE44/AAF40/AAG38/AAH41: + * + * A race condition between speculative fetches and invalidating + * a large page. This is worked around in microcode, but we + * need the microcode to have already been loaded... so if it is + * not, recommend a BIOS update and disable large pages. + */ + if (c->x86 == 6 && c->x86_model == 0x1c && c->x86_mask <= 2) { + u32 ucode, junk; + + wrmsr(MSR_IA32_UCODE_REV, 0, 0); + sync_core(); + rdmsr(MSR_IA32_UCODE_REV, junk, ucode); + + if (ucode < 0x20e) { + printk(KERN_WARNING "Atom PSE erratum detected, BIOS microcode update recommended\n"); + clear_cpu_cap(c, X86_FEATURE_PSE); + } + } + #ifdef CONFIG_X86_64 set_cpu_cap(c, X86_FEATURE_SYSENTER32); #else -- 2.39.5