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[35.185.214.157]) by smtp.gmail.com with ESMTPSA id v63sm3437412pgv.59.2021.08.13.09.35.40 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 13 Aug 2021 09:35:40 -0700 (PDT) Date: Fri, 13 Aug 2021 16:35:34 +0000 From: Sean Christopherson To: Jim Mattson Cc: Oliver Upton , kvm@vger.kernel.org, Paolo Bonzini , Peter Shier Subject: Re: [PATCH v2 4/5] KVM: nVMX: Emulate MTF when performing instruction emulation Message-ID: References: <20200128092715.69429-1-oupton@google.com> <20200128092715.69429-5-oupton@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Thu, Aug 12, 2021, Jim Mattson wrote: > On Tue, Jan 28, 2020 at 1:27 AM Oliver Upton wrote: > > > > Since commit 5f3d45e7f282 ("kvm/x86: add support for > > MONITOR_TRAP_FLAG"), KVM has allowed an L1 guest to use the monitor trap > > flag processor-based execution control for its L2 guest. KVM simply > > forwards any MTF VM-exits to the L1 guest, which works for normal > > instruction execution. > > > > However, when KVM needs to emulate an instruction on the behalf of an L2 > > guest, the monitor trap flag is not emulated. Add the necessary logic to > > kvm_skip_emulated_instruction() to synthesize an MTF VM-exit to L1 upon > > instruction emulation for L2. > > > > Fixes: 5f3d45e7f282 ("kvm/x86: add support for MONITOR_TRAP_FLAG") > > Signed-off-by: Oliver Upton > > --- ... > > diff --git a/arch/x86/include/uapi/asm/kvm.h b/arch/x86/include/uapi/asm/kvm.h > > index 503d3f42da16..3f3f780c8c65 100644 > > --- a/arch/x86/include/uapi/asm/kvm.h > > +++ b/arch/x86/include/uapi/asm/kvm.h > > @@ -390,6 +390,7 @@ struct kvm_sync_regs { > > #define KVM_STATE_NESTED_GUEST_MODE 0x00000001 > > #define KVM_STATE_NESTED_RUN_PENDING 0x00000002 > > #define KVM_STATE_NESTED_EVMCS 0x00000004 > > +#define KVM_STATE_NESTED_MTF_PENDING 0x00000008 > > Maybe I don't understand the distinction, but shouldn't this new flag > have a KVM_STATE_NESTED_VMX prefix and live with > KVM_STATE_VMX_PREEMPTION_TIMER_DEADLINE, below? That does seem to be the case, seems highly unlikely SVM will add MTF. And SVM's KVM_STATE_NESTED_GIF_SET should have been SVM specific, but kvm_svm_nested_state_hdr doesn't even reserve a flags field :-/ > > #define KVM_STATE_NESTED_SMM_GUEST_MODE 0x00000001 > > #define KVM_STATE_NESTED_SMM_VMXON 0x00000002