From 072e054359a4d4a4f6c3fa09585667472c4f0f1d Mon Sep 17 00:00:00 2001 From: Sergey Dyasli Date: Tue, 23 Oct 2018 11:59:12 +0100 Subject: [PATCH] x86/boot: enable NMIs after traps init In certain scenarios, NMIs might be disabled during Xen boot process. Such situation will cause alternative_instructions() to: panic("Timed out waiting for alternatives self-NMI to hit\n"); This bug was originally seen when using Tboot to boot Xen 4.11 To prevent this from happening, enable NMIs during cpu_init() and during __start_xen() for BSP. Signed-off-by: Sergey Dyasli Reviewed-by: Andrew Cooper --- xen/arch/x86/cpu/common.c | 3 +++ xen/arch/x86/setup.c | 3 +++ 2 files changed, 6 insertions(+) diff --git a/xen/arch/x86/cpu/common.c b/xen/arch/x86/cpu/common.c index 057859ab14..9af2f307ad 100644 --- a/xen/arch/x86/cpu/common.c +++ b/xen/arch/x86/cpu/common.c @@ -819,6 +819,9 @@ void cpu_init(void) #define CD(register) asm volatile ( "mov %0,%%db" #register : : "r"(0UL) ); CD(0); CD(1); CD(2); CD(3); /* no db4 and db5 */; CD(6); CD(7); #undef CD + + /* Enable NMIs. Our loader (e.g. Tboot) may have left them disabled. */ + enable_nmis(); } void cpu_uninit(unsigned int cpu) diff --git a/xen/arch/x86/setup.c b/xen/arch/x86/setup.c index 93b79c7c0c..55a288f332 100644 --- a/xen/arch/x86/setup.c +++ b/xen/arch/x86/setup.c @@ -708,6 +708,9 @@ void __init noreturn __start_xen(unsigned long mbi_p) /* Full exception support from here on in. */ + /* Enable NMIs. Our loader (e.g. Tboot) may have left them disabled. */ + enable_nmis(); + if ( pvh_boot ) { /* -- 2.30.2