From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [PATCH] KVM: emulator: Only allow VMCALL/VMMCALL trapped by #UD Date: Mon, 07 Jan 2008 12:43:52 +0200 Message-ID: <47820268.9060309@qumranet.com> References: <200801040936.08670.sheng.yang@intel.com> <200801071021.12038.sheng.yang@intel.com> <4781EF63.4010201@qumranet.com> <200801071823.15040.sheng.yang@intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: kvm-devel-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org, Eric Liu To: "Yang, Sheng" Return-path: In-Reply-To: <200801071823.15040.sheng.yang-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: kvm-devel-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org Errors-To: kvm-devel-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org List-Id: kvm.vger.kernel.org Yang, Sheng wrote: > On Monday 07 January 2008 17:22:43 Avi Kivity wrote: > >> Yang, Sheng wrote: >> >>>> I have a vague plan for improving decode; basically extend the decode >>>> tables to add group decoding. We add a bit to opcode_table and >>>> twobyte_table that is set for all instructions which need group >>>> decoding. When the bit is set, the rest of the value in opcode_table is >>>> interpreted as an index (together with modrm_reg) into a new >>>> group_table, so we can have different decoding for such instructions. >>>> >>> I also have tried to propose a table for Grp opcode, but can't find a >>> easy way. Using the rest of the value in opcode_table is a good idea, but >>> I'm afraid the same value for different group exists, e.g. 0x82(Grp1) and >>> 0xc0 (Grp2) got the same value as: ByteOp | DstMem | SrcImm | ModRM. If >>> we add more factors to this, it would become unclear and more tricky, the >>> table also may become larger... >>> >>> Currently, if we want to using group_table, I think the straightforward >>> way is better: another big "switch"... The only exception is 1a, and we >>> may use 0 instead of it. >>> >> Not sure what you mean. I thought of adding code like >> >> >> if (c->d & Group) { >> c->group = c->d & GroupMask; >> > > I meant the c->d & GroupMask is not sufficient to indicate different group. > For example, 0x82(Grp1) and 0xc0(Grp2) have same c->d & GroupMask = ByteOp | > DstMem | SrcImm | ModRM. > > I now see the source of confusion... >> // fetch modrm_reg >> c->d = group_table[c->group * 8 + modrm_reg]; >> > > In this case, how can you deal with c->group = ByteOp | DstMem | SrcImm | > ModRM, and modrm_reg = 6. Is it a XOR or nothing? > In this case, we would have opcode_table[0x82] == Group | Grp1 (c->group == Grp1 == 1) opcode_table[0xc0] == Group | Grp2 (c->group == Grp2 == 2) group_table[Grp1 * 8 + 6] == ByteOp | DstMem | SrcImm | ModRM group_table[Grp2 * 8 + 0] == ByteOp | DstMem | SrcImm | ModRM If Group is set in opcode_table, the rest of the value is the group number, with the reg part used to pick the final decode flags. -- error compiling committee.c: too many arguments to function ------------------------------------------------------------------------- This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2005. http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/