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Koen Kooi
56e60917b2
Signed-off-by: Koen Kooi <koen@dominion.thruhere.net> Signed-off-by: Denys Dmytriyenko <denys@ti.com> Signed-off-by: Denys Dmytriyenko <denis@denix.org>
93 lines
2.7 KiB
Diff
93 lines
2.7 KiB
Diff
From 6a7d02f3957e572d5e35fc71df90a3a7311e383d Mon Sep 17 00:00:00 2001
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From: Borislav Petkov <borislav.petkov@amd.com>
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Date: Thu, 21 Jun 2012 14:07:16 +0200
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Subject: [PATCH 32/73] x86, microcode: Sanitize per-cpu microcode reloading
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interface
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commit c9fc3f778a6a215ace14ee556067c73982b6d40f upstream.
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Microcode reloading in a per-core manner is a very bad idea for both
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major x86 vendors. And the thing is, we have such interface with which
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we can end up with different microcode versions applied on different
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cores of an otherwise homogeneous wrt (family,model,stepping) system.
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So turn off the possibility of doing that per core and allow it only
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system-wide.
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This is a minimal fix which we'd like to see in stable too thus the
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more-or-less arbitrary decision to allow system-wide reloading only on
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the BSP:
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$ echo 1 > /sys/devices/system/cpu/cpu0/microcode/reload
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...
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and disable the interface on the other cores:
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$ echo 1 > /sys/devices/system/cpu/cpu23/microcode/reload
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-bash: echo: write error: Invalid argument
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Also, allowing the reload only from one CPU (the BSP in
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that case) doesn't allow the reload procedure to degenerate
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into an O(n^2) deal when triggering reloads from all
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/sys/devices/system/cpu/cpuX/microcode/reload sysfs nodes
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simultaneously.
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A more generic fix will follow.
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Cc: Henrique de Moraes Holschuh <hmh@hmh.eng.br>
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Cc: Peter Zijlstra <peterz@infradead.org>
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Signed-off-by: Borislav Petkov <borislav.petkov@amd.com>
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Link: http://lkml.kernel.org/r/1340280437-7718-2-git-send-email-bp@amd64.org
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Signed-off-by: H. Peter Anvin <hpa@zytor.com>
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Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
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---
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arch/x86/kernel/microcode_core.c | 26 +++++++++++++++++++-------
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1 files changed, 19 insertions(+), 7 deletions(-)
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diff --git a/arch/x86/kernel/microcode_core.c b/arch/x86/kernel/microcode_core.c
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index 19c7af1..29c95d7 100644
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--- a/arch/x86/kernel/microcode_core.c
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+++ b/arch/x86/kernel/microcode_core.c
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@@ -297,19 +297,31 @@ static ssize_t reload_store(struct sys_device *dev,
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const char *buf, size_t size)
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{
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unsigned long val;
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- int cpu = dev->id;
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- ssize_t ret = 0;
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+ int cpu;
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+ ssize_t ret = 0, tmp_ret;
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+
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+ /* allow reload only from the BSP */
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+ if (boot_cpu_data.cpu_index != dev->id)
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+ return -EINVAL;
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ret = kstrtoul(buf, 0, &val);
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if (ret)
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return ret;
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- if (val == 1) {
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- get_online_cpus();
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- if (cpu_online(cpu))
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- ret = reload_for_cpu(cpu);
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- put_online_cpus();
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+ if (val != 1)
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+ return size;
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+
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+ get_online_cpus();
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+ for_each_online_cpu(cpu) {
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+ tmp_ret = reload_for_cpu(cpu);
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+ if (tmp_ret != 0)
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+ pr_warn("Error reloading microcode on CPU %d\n", cpu);
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+
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+ /* save retval of the first encountered reload error */
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+ if (!ret)
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+ ret = tmp_ret;
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}
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+ put_online_cpus();
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if (!ret)
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ret = size;
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--
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1.7.7.6
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