Commit ad8f9e69 authored by Maxim Levitsky's avatar Maxim Levitsky Committed by Paolo Bonzini
Browse files

KVM: x86: emulator: update the emulation mode after CR0 write 



Update the emulation mode when handling writes to CR0, because
toggling CR0.PE switches between Real and Protected Mode, and toggling
CR0.PG when EFER.LME=1 switches between Long and Protected 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: default avatarMaxim Levitsky <mlevitsk@redhat.com>
Message-Id: <20221025124741.228045-14-mlevitsk@redhat.com>
Cc: stable@vger.kernel.org
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 055f37f8

arch/x86/kvm/emulate.c

+15 −1
Original line number Diff line number Diff line
@@ -3641,11 +3641,25 @@ 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 and/or CR0.PG

		 * which can affect the cpu's execution mode.

		 */

		r = emulator_recalc_and_set_mode(ctxt);

		if (r != X86EMUL_CONTINUE)

			return r;

	}



	return X86EMUL_CONTINUE;

}