From 08f27f4468eedbeccaac9fdda4ef732247efd74e Mon Sep 17 00:00:00 2001 From: Andrew Cooper Date: Mon, 16 Oct 2017 13:20:07 +0000 Subject: [PATCH] xen/pv: Construct d0v0's GDT properly c/s cf6d39f8199 "x86/PV: properly populate descriptor tables" changed the GDT to reference zero_page for intermediate frames between the guest and Xen frames. Because dom0_construct_pv() doesn't call arch_set_info_guest(), some bits of initialisation are missed, including the pv_destroy_gdt() which initially fills the references to zero_page. In practice, this means there is a window between starting and the first call to HYPERCALL_set_gdt() were lar/lsl/verr/verw suffer non-architectural behaviour. Signed-off-by: Andrew Cooper Reviewed-by: Jan Beulich --- This probably wants backporting to Xen 4.7 and later. --- xen/arch/x86/pv/dom0_build.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/xen/arch/x86/pv/dom0_build.c b/xen/arch/x86/pv/dom0_build.c index 44601d08d3..a13412efb9 100644 --- a/xen/arch/x86/pv/dom0_build.c +++ b/xen/arch/x86/pv/dom0_build.c @@ -18,6 +18,7 @@ #include #include #include +#include #include /* Allow ring-3 access in long mode as guest cannot use ring 1 ... */ @@ -866,6 +867,13 @@ int __init dom0_construct_pv(struct domain *d, regs->rsi = vstartinfo_start; regs->eflags = X86_EFLAGS_IF; + /* + * We don't call arch_set_info_guest(), so some initialisation needs doing + * by hand: + * - Reset the GDT to reference zero_page + */ + pv_destroy_gdt(v); + if ( test_bit(XENFEAT_supervisor_mode_kernel, parms.f_required) ) panic("Dom0 requires supervisor-mode execution"); -- 2.30.2