Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757508Ab3FCMxf (ORCPT ); Mon, 3 Jun 2013 08:53:35 -0400 Received: from mx1.redhat.com ([209.132.183.28]:17072 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754263Ab3FCMxa (ORCPT ); Mon, 3 Jun 2013 08:53:30 -0400 Message-ID: <51AC91BD.2030002@redhat.com> Date: Mon, 03 Jun 2013 14:53:17 +0200 From: Paolo Bonzini User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130514 Thunderbird/17.0.6 MIME-Version: 1.0 To: Gleb Natapov CC: kvm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] KVM: fix sil/dil/bpl/spl in the mod/rm fields References: <1369924555-30216-1-git-send-email-pbonzini@redhat.com> <51A7717D.6030203@redhat.com> <20130603102530.GH4725@redhat.com> In-Reply-To: <20130603102530.GH4725@redhat.com> X-Enigmail-Version: 1.5.1 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3955 Lines: 114 Il 03/06/2013 12:25, Gleb Natapov ha scritto: > On Thu, May 30, 2013 at 05:34:21PM +0200, Paolo Bonzini wrote: >> Il 30/05/2013 16:35, Paolo Bonzini ha scritto: >>> The x86-64 extended low-byte registers were fetched correctly from reg, >>> but not from mod/rm. >>> >>> This fixes another bug in the boot of RHEL5.9 64-bit, but it is still >>> not enough. >> >> Well, it is enough but it takes 2 minutes to reach the point where >> hardware virtualization is used. It is doing a lot of stuff in >> emulation mode because FS and GS have leftovers from the A20 test: >> >> FS =0000 0000000000000000 0000ffff 00009300 DPL=0 DS16 [-WA] >> GS =ffff 00000000000ffff0 0000ffff 00009300 DPL=0 DS16 [-WA] >> >> 0x00000000000113be: in $0x92,%al >> 0x00000000000113c0: or $0x2,%al >> 0x00000000000113c2: out %al,$0x92 >> 0x00000000000113c4: xor %ax,%ax >> 0x00000000000113c6: mov %ax,%fs >> 0x00000000000113c8: dec %ax >> 0x00000000000113c9: mov %ax,%gs >> 0x00000000000113cb: inc %ax >> 0x00000000000113cc: mov %ax,%fs:0x200 >> 0x00000000000113d0: cmp %gs:0x210,%ax >> 0x00000000000113d5: je 0x113cb >> > This is 16 bit code that sets them up. So 32bit transition code does not > reload them? Yes. It does this: movw $1, %ax # protected mode (PE) bit lmsw %ax # This is it! jmp flush_instr flush_instr: xorw %bx, %bx # Flag to indicate a boot xorl %esi, %esi # Pointer to real-mode code movw %cs, %si subw $DELTA_INITSEG, %si shll $4, %esi # Convert to 32-bit pointer .byte 0x66, 0xea # prefix + jmpi-opcode code32: .long 0x1000 # will be set to 0x100000 # for big kernels .word __KERNEL_CS which jumps to boot/compressed/head.S: startup_32: cld cli movl $(__KERNEL_DS), %eax movl %eax, %ds movl %eax, %es movl %eax, %ss and totally ignores fs/gs. Much later there is this (in kernel/head.S): /* * We don't really need to load %fs or %gs, but load them anyway * to kill any stale realmode selectors. This allows execution * under VT hardware. */ movl %eax,%fs movl %eax,%gs but the whole decompression is run under emulation. Paolo >> The DPL < RPL test fails. Any ideas? Should we introduce a new >> intermediate value for emulate_invalid_guest_state (0=none, 1=some, 2=full)? >> >> Paolo >> >>> Cc: gnatapov@redhat.com >>> Cc: kvm@vger.kernel.org >>> Cc: # 3.9 >>> Signed-off-by: Paolo Bonzini >>> --- >>> arch/x86/kvm/emulate.c | 5 ++++- >>> 1 file changed, 4 insertions(+), 1 deletion(-) >>> >>> diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c >>> index aa68106..028b34f 100644 >>> --- a/arch/x86/kvm/emulate.c >>> +++ b/arch/x86/kvm/emulate.c >>> @@ -1239,9 +1239,12 @@ static int decode_modrm(struct x86_emulate_ctxt *ctxt, >>> ctxt->modrm_seg = VCPU_SREG_DS; >>> >>> if (ctxt->modrm_mod == 3) { >>> + int highbyte_regs = ctxt->rex_prefix == 0; >>> + >>> op->type = OP_REG; >>> op->bytes = (ctxt->d & ByteOp) ? 1 : ctxt->op_bytes; >>> - op->addr.reg = decode_register(ctxt, ctxt->modrm_rm, ctxt->d & ByteOp); >>> + op->addr.reg = decode_register(ctxt, ctxt->modrm_rm, >>> + highbyte_regs && (ctxt->d & ByteOp)); >>> if (ctxt->d & Sse) { >>> op->type = OP_XMM; >>> op->bytes = 16; >>> > > -- > Gleb. > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/