[Linux-stable-mirror] [PATCH 1/2] x86/microcode/AMD: Do not load when running on a hypervisor
From: Borislav Petkov bp@suse.de
commit a15a753539eca8ba243d576f02e7ca9c4b7d7042 upstream with minor adjustments.
Doing so is completely void of sense for multiple reasons so prevent it. Set dis_ucode_ldr to true and thus disable the microcode loader by default to address xen pv guests which execute the AP path but not the BSP path.
By having it turned off by default, the APs won't run into the loader either.
Also, check CPUID(1).ECX[31] which hypervisors set. Well almost, not the xen pv one. That one gets the aforementioned "fix".
Also, improve the detection method by caching the final decision whether to continue loading in dis_ucode_ldr and do it once on the BSP. The APs then simply test that value.
Signed-off-by: Borislav Petkov bp@suse.de Tested-by: Juergen Gross jgross@suse.com Tested-by: Boris Ostrovsky boris.ostrovsky@oracle.com Acked-by: Juergen Gross jgross@suse.com Link: http://lkml.kernel.org/r/20161218164414.9649-4-bp@alien8.de Signed-off-by: Thomas Gleixner tglx@linutronix.de Cc: stable@vger.kernel.org # 4.4.x Signed-off-by: Rolf Neugebauer rolf.neugebauer@docker.com --- arch/x86/kernel/cpu/microcode/core.c | 28 +++++++++++++++++++--------- 1 file changed, 19 insertions(+), 9 deletions(-)
diff --git a/arch/x86/kernel/cpu/microcode/core.c b/arch/x86/kernel/cpu/microcode/core.c index b3e94ef461fd..1b3e0aa4c511 100644 --- a/arch/x86/kernel/cpu/microcode/core.c +++ b/arch/x86/kernel/cpu/microcode/core.c @@ -44,7 +44,7 @@
static struct microcode_ops *microcode_ops;
-static bool dis_ucode_ldr; +static bool dis_ucode_ldr = true;
static int __init disable_loader(char *str) { @@ -81,6 +81,7 @@ struct cpu_info_ctx {
static bool __init check_loader_disabled_bsp(void) { + u32 a, b, c, d; #ifdef CONFIG_X86_32 const char *cmdline = (const char *)__pa_nodebug(boot_command_line); const char *opt = "dis_ucode_ldr"; @@ -93,8 +94,23 @@ static bool __init check_loader_disabled_bsp(void) bool *res = &dis_ucode_ldr; #endif
- if (cmdline_find_option_bool(cmdline, option)) - *res = true; + if (!have_cpuid_p()) + return *res; + + a = 1; + c = 0; + native_cpuid(&a, &b, &c, &d); + + /* + * CPUID(1).ECX[31]: reserved for hypervisor use. This is still not + * completely accurate as xen pv guests don't see that CPUID bit set but + * that's good enough as they don't land on the BSP path anyway. + */ + if (c & BIT(31)) + return *res; + + if (cmdline_find_option_bool(cmdline, option) <= 0) + *res = false;
return *res; } @@ -126,9 +142,6 @@ void __init load_ucode_bsp(void) if (check_loader_disabled_bsp()) return;
- if (!have_cpuid_p()) - return; - vendor = x86_vendor(); family = x86_family();
@@ -162,9 +175,6 @@ void load_ucode_ap(void) if (check_loader_disabled_ap()) return;
- if (!have_cpuid_p()) - return; - vendor = x86_vendor(); family = x86_family();
From: Borislav Petkov bp@suse.de
commit 1f161f67a272cc4f29f27934dd3f74cb657eb5c4 upstream with adjustments.
On CPUs like AMD's Geode, for example, we shouldn't even try to load microcode because they do not support the modern microcode loading interface.
However, we do the family check *after* the other checks whether the loader has been disabled on the command line or whether we're running in a guest.
So move the family checks first in order to exit early if we're being loaded on an unsupported family.
Reported-and-tested-by: Sven Glodowski glodi1@arcor.de Signed-off-by: Borislav Petkov bp@suse.de Cc: stable@vger.kernel.org # 4.11.. Cc: Linus Torvalds torvalds@linux-foundation.org Cc: Peter Zijlstra peterz@infradead.org Cc: Thomas Gleixner tglx@linutronix.de Link: http://bugzilla.suse.com/show_bug.cgi?id=1061396 Link: http://lkml.kernel.org/r/20171012112316.977-1-bp@alien8.de Signed-off-by: Ingo Molnar mingo@kernel.org Cc: stable@vger.kernel.org # 4.4.x Signed-off-by: Rolf Neugebauer rolf.neugebauer@docker.com --- arch/x86/kernel/cpu/microcode/core.c | 27 ++++++++++++++++++--------- 1 file changed, 18 insertions(+), 9 deletions(-)
diff --git a/arch/x86/kernel/cpu/microcode/core.c b/arch/x86/kernel/cpu/microcode/core.c index 1b3e0aa4c511..ce5f8a2e7ae6 100644 --- a/arch/x86/kernel/cpu/microcode/core.c +++ b/arch/x86/kernel/cpu/microcode/core.c @@ -94,9 +94,6 @@ static bool __init check_loader_disabled_bsp(void) bool *res = &dis_ucode_ldr; #endif
- if (!have_cpuid_p()) - return *res; - a = 1; c = 0; native_cpuid(&a, &b, &c, &d); @@ -138,8 +135,9 @@ void __init load_ucode_bsp(void) { int vendor; unsigned int family; + bool intel = true;
- if (check_loader_disabled_bsp()) + if (!have_cpuid_p()) return;
vendor = x86_vendor(); @@ -147,16 +145,27 @@ void __init load_ucode_bsp(void)
switch (vendor) { case X86_VENDOR_INTEL: - if (family >= 6) - load_ucode_intel_bsp(); + if (family < 6) + return; break; + case X86_VENDOR_AMD: - if (family >= 0x10) - load_ucode_amd_bsp(family); + if (family < 0x10) + return; + intel = false; break; + default: - break; + return; } + + if (check_loader_disabled_bsp()) + return; + + if (intel) + load_ucode_intel_bsp(); + else + load_ucode_amd_bsp(family); }
static bool check_loader_disabled_ap(void)
On Thu, Feb 08, 2018 at 05:12:04PM +0000, Rolf Neugebauer wrote:
From: Borislav Petkov bp@suse.de
commit 1f161f67a272cc4f29f27934dd3f74cb657eb5c4 upstream with adjustments.
This also seems to work for 4.9, thanks! Both now queued up.
greg k-h
linux-stable-mirror@lists.linaro.org
-
Greg KH -
Rolf Neugebauer