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[35.185.214.157]) by smtp.gmail.com with ESMTPSA id j6sm2852801pfn.107.2021.09.22.08.52.43 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 22 Sep 2021 08:52:43 -0700 (PDT) Date: Wed, 22 Sep 2021 15:52:40 +0000 From: Sean Christopherson To: Paolo Bonzini Cc: Maxim Levitsky , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Jim Mattson , Wanpeng Li , Thomas Gleixner , "H. Peter Anvin" , Borislav Petkov , Vitaly Kuznetsov , Ingo Molnar , "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" , Joerg Roedel Subject: Re: [PATCH v3 0/7] KVM: few more SMM fixes Message-ID: References: <20210913140954.165665-1-mlevitsk@redhat.com> <22916f0c-2e3a-1fd6-905e-5d647c15c45b@redhat.com> <427038b4-a856-826c-e9f4-01678d33ab83@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <427038b4-a856-826c-e9f4-01678d33ab83@redhat.com> Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Wed, Sep 22, 2021, Paolo Bonzini wrote: > On 22/09/21 16:46, Sean Christopherson wrote: > > On Wed, Sep 22, 2021, Paolo Bonzini wrote: > > > On 13/09/21 16:09, Maxim Levitsky wrote: > > > > KVM: x86: nVMX: re-evaluate emulation_required on nested VM exit > > > > ... > > > Queued, thanks. However, I'm keeping patch 1 for 5.16 only. > > > > I'm pretty sure the above patch is wrong, emulation_required can simply be > > cleared on emulated VM-Exit. > > Are you sure? Pretty sure, but not 100% sure :-) > I think you can at least set the host segment fields to a data segment that > requires emulation. For example the DPL of the host DS is hardcoded to zero, > but the RPL comes from the selector field and the DS selector is not > validated. HOST_DS_SEL is validated: In the selector field for each of CS, SS, DS, ES, FS, GS and TR, the RPL (bits 1:0) and the TI flag (bit 2) must be 0. > Therefore a subsequent vmentry could fail the access rights tests of 26.3.1.2 > Checks on Guest Segment Registers: Yes, but this path is loading host state on VM-Exit. > DS, ES, FS, GS. The DPL cannot be less than the RPL in the selector field if > (1) the “unrestricted guest” VM-execution control is 0; (2) the register is > usable; and (3) the Type in the access-rights field is in the range 0 – 11 > (data segment or non-conforming code segment). > > Paolo >