From 5c7411e2937401bf4d024744032f879475364996 Mon Sep 17 00:00:00 2001 From: Nadav Amit Date: Mon, 7 Apr 2014 18:37:47 +0300 Subject: [PATCH] KVM: x86: Fix CR3 and LDT sel should not be saved in TSS According to Intel specifications, only general purpose registers and segment selectors should be saved in the old TSS during 32-bit task-switch. Signed-off-by: Nadav Amit Signed-off-by: Marcelo Tosatti --- arch/x86/kvm/emulate.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-) diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c index 205b17eed93c..0dec502d20be 100644 --- a/arch/x86/kvm/emulate.c +++ b/arch/x86/kvm/emulate.c @@ -2496,7 +2496,7 @@ static int task_switch_16(struct x86_emulate_ctxt *ctxt, static void save_state_to_tss32(struct x86_emulate_ctxt *ctxt, struct tss_segment_32 *tss) { - tss->cr3 = ctxt->ops->get_cr(ctxt, 3); + /* CR3 and ldt selector are not saved intentionally */ tss->eip = ctxt->_eip; tss->eflags = ctxt->eflags; tss->eax = reg_read(ctxt, VCPU_REGS_RAX); @@ -2514,7 +2514,6 @@ static void save_state_to_tss32(struct x86_emulate_ctxt *ctxt, tss->ds = get_segment_selector(ctxt, VCPU_SREG_DS); tss->fs = get_segment_selector(ctxt, VCPU_SREG_FS); tss->gs = get_segment_selector(ctxt, VCPU_SREG_GS); - tss->ldt_selector = get_segment_selector(ctxt, VCPU_SREG_LDTR); } static int load_state_from_tss32(struct x86_emulate_ctxt *ctxt, @@ -2604,6 +2603,8 @@ static int task_switch_32(struct x86_emulate_ctxt *ctxt, struct tss_segment_32 tss_seg; int ret; u32 new_tss_base = get_desc_base(new_desc); + u32 eip_offset = offsetof(struct tss_segment_32, eip); + u32 ldt_sel_offset = offsetof(struct tss_segment_32, ldt_selector); ret = ops->read_std(ctxt, old_tss_base, &tss_seg, sizeof tss_seg, &ctxt->exception); @@ -2613,8 +2614,9 @@ static int task_switch_32(struct x86_emulate_ctxt *ctxt, save_state_to_tss32(ctxt, &tss_seg); - ret = ops->write_std(ctxt, old_tss_base, &tss_seg, sizeof tss_seg, - &ctxt->exception); + /* Only GP registers and segment selectors are saved */ + ret = ops->write_std(ctxt, old_tss_base + eip_offset, &tss_seg.eip, + ldt_sel_offset - eip_offset, &ctxt->exception); if (ret != X86EMUL_CONTINUE) /* FIXME: need to provide precise fault address */ return ret; -- 2.20.1