Messages in this thread | | | Date | Fri, 10 Apr 2020 20:25:38 +0900 | From | Masami Hiramatsu <> | Subject | Re: [PATCH 3/4] x86,module: Detect VMX vs SLD conflicts |
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On Wed, 8 Apr 2020 11:56:04 +0200 Peter Zijlstra <peterz@infradead.org> wrote:
> On Wed, Apr 08, 2020 at 05:09:34PM +0900, Masami Hiramatsu wrote: > > On Tue, 07 Apr 2020 13:02:39 +0200 > > Peter Zijlstra <peterz@infradead.org> wrote: > > > > > +static bool insn_is_vmx(struct insn *insn) > > > +{ > > > + u8 modrm = insn->modrm.bytes[0]; > > > + u8 modrm_mod = X86_MODRM_MOD(modrm); > > > + u8 modrm_reg = X86_MODRM_REG(modrm); > > > + > > > + u8 prefix = insn->prefixes.bytes[0]; > > > > This should be the last prefix, > > > > u8 prefix = insn->prefixes.bytes[3]; > > > > (The last prefix always copied on the bytes[3]) > > And that is 0 on no-prefix, right?
Yes, it should be.
> > > + > > > + if (insn->opcode.bytes[0] != 0x0f) > > > + return false; > > > + > > > + switch (insn->opcode.bytes[1]) { > > > + case 0x01: > > > + switch (insn->opcode.bytes[2]) { > > > > Sorry, VMCALL etc. is in Grp7 (0f 01), the 3rd code is embedded > > in modrm instead of opcode. Thus it should be, > > > > switch (insn->modrm.value) { > > Indeed, I was hoping (I really should've checked) that that byte was > duplicated in opcodes. > > Also, since I already have modrm = insn->modrm.bytes[0], I should > probably use that anyway.
Yeah, and please use modrm.value instead of bytes[0]. (maybe bytes[0] will be OK since x86 is little-endian)
> > > + case 0xc1: /* VMCALL */ > > > + case 0xc2: /* VMLAUNCH */ > > > + case 0xc3: /* VMRESUME */ > > > + case 0xc4: /* VMXOFF */ > > > > case 0xd4: /* VMFUNC */ > > As per Andrew, VMCALL and VMFUNC are SMV, and I really only need VMX in > this case. Including SMV is probably harmless, but I'm thinking a > smaller function is better.
I got it.
> > > > + return true; > > > + > > > + default: > > > + break; > > > + } > > > + break; > > > + > > > + case 0x78: /* VMREAD */ > > > + case 0x79: /* VMWRITE */ > > > > return !insn_is_evex(insn); > > > > With EVEX prefix, these becomes vcvt* instructions. > > Thanks!
Thank you,
-- Masami Hiramatsu <mhiramat@kernel.org>
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