From mboxrd@z Thu Jan  1 00:00:00 1970
From: Radim =?utf-8?B?S3LEjW3DocWZ?= <rkrcmar@redhat.com>
Subject: Re: [RFC PATCH 3/4] KVM: x86: add support for emulating UMIP
Date: Thu, 14 Jul 2016 14:24:13 +0200
Message-ID: <20160714122413.GG21976@potion>
References: <1468351223-3250-1-git-send-email-pbonzini@redhat.com>
 <1468351223-3250-4-git-send-email-pbonzini@redhat.com>
 <20160713200321.GA16130@potion>
 <af995640-7f54-18ea-0589-f04d8ec9b054@redhat.com>
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Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org
To: Paolo Bonzini <pbonzini@redhat.com>
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2016-07-14 09:00+0200, Paolo Bonzini:
> On 13/07/2016 22:03, Radim Kr=C4=8Dm=C3=A1=C5=99 wrote:
>> 2016-07-12 21:20+0200, Paolo Bonzini:
>>> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
>>> ---
>>> diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
>>> @@ -3738,6 +3747,10 @@ static int em_lidt(struct x86_emulate_ctxt *=
ctxt)
>>> =20
>>>  static int em_smsw(struct x86_emulate_ctxt *ctxt)
>>>  {
>>> +	if ((ctxt->ops->get_cr(ctxt, 4) & X86_CR4_UMIP) &&
>>> +	    ctxt->ops->cpl(ctxt) > 0)
>>=20
>> UMIP should #GP(0) in virtual-8086 mode too (for SMSW, SIDT, and SGD=
T),
>> but cpl() returns 0 in vm86.
>=20
> No, it returns 3.
>=20
> vmx->rmode.vm86_active means "there is no unrestricted guest support,
> and we're using VM86 mode to emulate real mode".  The special case in
> vmx_get_cpl is needed exactly because real mode CPL is 0 but VM86 has
> CPL 3.  In fact fix_rmode_seg sets DPL=3D3 for all segments, and CPL=3D=
SS.DPL.

Right, thanks.