From: Roger Pau Monné Date: Fri, 6 Sep 2019 15:04:39 +0000 (+0200) Subject: x86/xstate: make use_xsave non-init X-Git-Url: http://xenbits.xensource.com/gitweb?a=commitdiff_plain;h=021eb25a294c388c9b0124200bf2080c1e88eb83;p=people%2Fliuw%2Fxen.git x86/xstate: make use_xsave non-init LLVM code generation can attempt to load from a variable in the next condition of an expression under certain circumstances, thus attempting to load use_xsave regardless of the value of the bsp variable, which leads to a page fault when the init section has already been unmapped. Fix this by making use_xsave non-init, thus preventing the page fault; use __read_mostly instead. The LLVM bug with the discussion about this issue can be found at: https://bugs.llvm.org/show_bug.cgi?id=39707 Signed-off-by: Roger Pau Monné Acked-by: Jan Beulich --- diff --git a/xen/arch/x86/xstate.c b/xen/arch/x86/xstate.c index 10016a05d0..243495ed07 100644 --- a/xen/arch/x86/xstate.c +++ b/xen/arch/x86/xstate.c @@ -576,7 +576,11 @@ unsigned int xstate_ctxt_size(u64 xcr0) /* Collect the information of processor's extended state */ void xstate_init(struct cpuinfo_x86 *c) { - static bool __initdata use_xsave = true; + /* + * NB: use_xsave cannot live in initdata because llvm might optimize + * reading it, see: https://bugs.llvm.org/show_bug.cgi?id=39707 + */ + static bool __read_mostly use_xsave = true; boolean_param("xsave", use_xsave); bool bsp = c == &boot_cpu_data;