Currently, setting a large (i.e. negative) base address for %cs does not work on a 64-bit host. The "JOS" teaching operating system, used by MIT and other universities, relies on such segments while bootstrapping its way to full virtual memory management.
Signed-off-by: Nelson Elhage <[email protected]> --- arch/x86/kvm/emulate.c | 5 ++++- 1 files changed, 4 insertions(+), 1 deletions(-) diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c index 0ad47b8..54e84b2 100644 --- a/arch/x86/kvm/emulate.c +++ b/arch/x86/kvm/emulate.c @@ -505,9 +505,12 @@ static int do_fetch_insn_byte(struct x86_emulate_ctxt *ctxt, int size, cur_size; if (eip == fc->end) { + unsigned long linear = eip + ctxt->cs_base; + if (ctxt->mode != X86EMUL_MODE_PROT64) + linear &= (u32)-1; cur_size = fc->end - fc->start; size = min(15UL - cur_size, PAGE_SIZE - offset_in_page(eip)); - rc = ops->fetch(ctxt->cs_base + eip, fc->data + cur_size, + rc = ops->fetch(linear, fc->data + cur_size, size, ctxt->vcpu, &ctxt->exception); if (rc != X86EMUL_CONTINUE) return rc; -- 1.7.2.43.g36c08.dirty -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
