Commit a15a7535 authored by Borislav Petkov's avatar Borislav Petkov Committed by Thomas Gleixner

x86/microcode/AMD: Do not load when running on a hypervisor

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: default avatarBorislav Petkov <bp@suse.de>
Tested-by: default avatarJuergen Gross <jgross@suse.com>
Tested-by: default avatarBoris Ostrovsky <boris.ostrovsky@oracle.com>
Acked-by: default avatarJuergen Gross <jgross@suse.com>
Link: http://lkml.kernel.org/r/20161218164414.9649-4-bp@alien8.deSigned-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
parent 200d3553
......@@ -44,7 +44,7 @@
#define DRIVER_VERSION "2.2"
static struct microcode_ops *microcode_ops;
static bool dis_ucode_ldr;
static bool dis_ucode_ldr = true;
LIST_HEAD(microcode_cache);
......@@ -76,6 +76,7 @@ struct cpu_info_ctx {
static bool __init check_loader_disabled_bsp(void)
{
static const char *__dis_opt_str = "dis_ucode_ldr";
u32 a, b, c, d;
#ifdef CONFIG_X86_32
const char *cmdline = (const char *)__pa_nodebug(boot_command_line);
......@@ -88,8 +89,23 @@ 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;
}
......@@ -121,9 +137,6 @@ void __init load_ucode_bsp(void)
if (check_loader_disabled_bsp())
return;
if (!have_cpuid_p())
return;
vendor = x86_cpuid_vendor();
family = x86_cpuid_family();
......@@ -157,9 +170,6 @@ void load_ucode_ap(void)
if (check_loader_disabled_ap())
return;
if (!have_cpuid_p())
return;
vendor = x86_cpuid_vendor();
family = x86_cpuid_family();
......
Markdown is supported
0%
or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment