From mboxrd@z Thu Jan 1 00:00:00 1970 From: Nadav Amit Subject: Re: [PATCH 5/5] KVM: x86: Fix wrong masking on relative jump/call Date: Wed, 07 May 2014 18:57:24 +0300 Message-ID: <536A57E4.10704@gmail.com> References: <1399465972-4026-1-git-send-email-namit@cs.technion.ac.il> <1399465972-4026-6-git-send-email-namit@cs.technion.ac.il> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: mtosatti@redhat.com, pbonzini@redhat.com, hpa@zytor.com, gleb@kernel.org, tglx@linutronix.de, mingo@redhat.com, x86@kernel.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org To: Bandan Das , Nadav Amit Return-path: In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org On 5/7/14, 5:43 PM, Bandan Das wrote: > Nadav Amit writes: > >> Relative jumps and calls do the masking according to the operand size, and not >> according to the address size as the KVM emulator does today. In 64-bit mode, >> the resulting RIP is always 64-bit. Otherwise it is masked according to the >> instruction operand-size. Note that when 16-bit address size is used, bits >> 63:32 are unmodified. >> >> Signed-off-by: Nadav Amit >> --- >> arch/x86/kvm/emulate.c | 4 +++- >> 1 file changed, 3 insertions(+), 1 deletion(-) >> >> diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c >> index 6833b41..e406705 100644 >> --- a/arch/x86/kvm/emulate.c >> +++ b/arch/x86/kvm/emulate.c >> @@ -506,7 +506,9 @@ static void rsp_increment(struct x86_emulate_ctxt *ctxt, int inc) >> >> static inline void jmp_rel(struct x86_emulate_ctxt *ctxt, int rel) >> { >> - register_address_increment(ctxt, &ctxt->_eip, rel); >> + /* 64-bit mode relative jumps are always 64-bit; otherwise mask */ >> + int op_bytes = ctxt->mode == X86EMUL_MODE_PROT64 ? 8 : ctxt->op_bytes; > > Just a nit, probably break this up for readability ? > I will make it more readable on the next version. Thanks, Nadav