From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001 From: Maxim Levitsky Date: Tue, 21 Jun 2022 18:08:56 +0300 Subject: [PATCH] KVM: x86: emulator: update the emulation mode after CR0 write CR0.PE toggles real/protected mode, thus its update should update the emulation mode. This is likely a benign bug because there is no writeback of state, other than the RIP increment, and when toggling CR0.PE, the CPU has to execute code from a very low memory address. Signed-off-by: Maxim Levitsky Signed-off-by: Thomas Lamprecht --- arch/x86/kvm/emulate.c | 13 ++++++++++++- 1 file changed, 12 insertions(+), 1 deletion(-) diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c index c582639ea2b4..38d9bfa650ec 100644 --- a/arch/x86/kvm/emulate.c +++ b/arch/x86/kvm/emulate.c @@ -3636,11 +3636,22 @@ static int em_movbe(struct x86_emulate_ctxt *ctxt) static int em_cr_write(struct x86_emulate_ctxt *ctxt) { - if (ctxt->ops->set_cr(ctxt, ctxt->modrm_reg, ctxt->src.val)) + int cr_num = ctxt->modrm_reg; + int r; + + if (ctxt->ops->set_cr(ctxt, cr_num, ctxt->src.val)) return emulate_gp(ctxt, 0); /* Disable writeback. */ ctxt->dst.type = OP_NONE; + + if (cr_num == 0) { + /* CR0 write might have updated CR0.PE */ + r = update_emulation_mode(ctxt); + if (r != X86EMUL_CONTINUE) + return r; + } + return X86EMUL_CONTINUE; }