From d80af845de7a4db01a4a3b4d779e0e0dcb5e738b Mon Sep 17 00:00:00 2001 From: Juergen Gross Date: Mon, 23 Apr 2018 16:13:01 +0200 Subject: [PATCH] xpti: fix bug in double fault handling When entering the hypervisor via the double fault handler resetting xen_cr3 was missing. This led to switching to pv_cr3 when returning from the next following exception, so repair this in order to allow exception handling to work even after a double fault. Signed-off-by: Juergen Gross Reviewed-by: Andrew Cooper Tested-by: Andrew Cooper Reviewed-by: Jan Beulich --- xen/arch/x86/x86_64/entry.S | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/xen/arch/x86/x86_64/entry.S b/xen/arch/x86/x86_64/entry.S index 45d9842d09..1cd7d93892 100644 --- a/xen/arch/x86/x86_64/entry.S +++ b/xen/arch/x86/x86_64/entry.S @@ -767,12 +767,14 @@ ENTRY(double_fault) /* WARNING! `ret`, `call *`, `jmp *` not safe before this point. */ mov STACK_CPUINFO_FIELD(xen_cr3)(%r14), %rbx - test %rbx, %rbx + neg %rbx jz .Ldblf_cr3_okay jns .Ldblf_cr3_load + mov %rbx, STACK_CPUINFO_FIELD(xen_cr3)(%r14) neg %rbx .Ldblf_cr3_load: mov %rbx, %cr3 + movq $0, STACK_CPUINFO_FIELD(xen_cr3)(%r14) .Ldblf_cr3_okay: movq %rsp,%rdi -- 2.30.2