| From a18a0f6850d4b286a5ebf02cd5b22fe496b86349 Mon Sep 17 00:00:00 2001 |
| From: Boris Ostrovsky <boris.ostrovsky@oracle.com> |
| Date: Mon, 1 Dec 2014 16:27:44 -0500 |
| Subject: x86, microcode: Don't initialize microcode code on paravirt |
| |
| From: Boris Ostrovsky <boris.ostrovsky@oracle.com> |
| |
| commit a18a0f6850d4b286a5ebf02cd5b22fe496b86349 upstream. |
| |
| Paravirtual guests are not expected to load microcode into processors |
| and therefore it is not necessary to initialize microcode loading |
| logic. |
| |
| In fact, under certain circumstances initializing this logic may cause |
| the guest to crash. Specifically, 32-bit kernels use __pa_nodebug() |
| macro which does not work in Xen (the code path that leads to this macro |
| happens during resume when we call mc_bp_resume()->load_ucode_ap() |
| ->check_loader_disabled_ap()) |
| |
| Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com> |
| Link: http://lkml.kernel.org/r/1417469264-31470-1-git-send-email-boris.ostrovsky@oracle.com |
| Signed-off-by: Borislav Petkov <bp@suse.de> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| |
| --- |
| arch/x86/kernel/cpu/microcode/core.c | 2 +- |
| 1 file changed, 1 insertion(+), 1 deletion(-) |
| |
| --- a/arch/x86/kernel/cpu/microcode/core.c |
| +++ b/arch/x86/kernel/cpu/microcode/core.c |
| @@ -559,7 +559,7 @@ static int __init microcode_init(void) |
| struct cpuinfo_x86 *c = &cpu_data(0); |
| int error; |
| |
| - if (dis_ucode_ldr) |
| + if (paravirt_enabled() || dis_ucode_ldr) |
| return 0; |
| |
| if (c->x86_vendor == X86_VENDOR_INTEL) |
