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AJvYcCVL4Gj0lvuANM3xil3mgqZpwcCf/3uN50aeTjNd6Zfd+FSY/LWSRzZNtoX6wqnU4hxrf6jn2HO3JRGpX12bcVlxWhYg X-Gm-Message-State: AOJu0Yx6GLuE59aOsRt1D4dzn+kjtseaHeglKvEAU/9u2+WKC1W0mHN4 tkqIpHzQ9Tfwa0Gl5l97mCeiBmozUasCGr+HHJR/iYlhAEkp5PJ79Gcljv+bMWzQ8ovaLXIwhiZ EYQ== X-Google-Smtp-Source: AGHT+IFIfK+eqnhmcLSPMAG/2/9f1SQvL+KnYDknKQLvZL6gpVpiqXrA/TZdD9ucj2QznvP7LERttljKVPg= X-Received: from zagreus.c.googlers.com ([fda3:e722:ac3:cc00:7f:e700:c0a8:5c37]) (user=seanjc job=sendgmr) by 2002:a17:903:2352:b0:1e4:5973:dbdc with SMTP id c18-20020a170903235200b001e45973dbdcmr410280plh.7.1715005318377; Mon, 06 May 2024 07:21:58 -0700 (PDT) Date: Mon, 6 May 2024 07:21:57 -0700 In-Reply-To: Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20240403184216.GJ2444378@ls.amr.corp.intel.com> <43cbaf90-7af3-4742-97b7-2ea587b16174@intel.com> <20240501155620.GA13783@ls.amr.corp.intel.com> <399cec29-ddf4-4dd5-a34b-ffec72cbfa26@intel.com> Message-ID: Subject: Re: [PATCH v19 101/130] KVM: TDX: handle ept violation/misconfig exit From: Sean Christopherson To: Chao Gao Cc: Reinette Chatre , Isaku Yamahata , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, isaku.yamahata@gmail.com, Paolo Bonzini , erdemaktas@google.com, Sagi Shahar , Kai Huang , chen.bo@intel.com, hang.yuan@intel.com, tina.zhang@intel.com, isaku.yamahata@linux.intel.com Content-Type: text/plain; charset="us-ascii" On Mon, May 06, 2024, Chao Gao wrote: > On Wed, May 01, 2024 at 09:54:07AM -0700, Reinette Chatre wrote: > >diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c > >index 499c6cd9633f..ba81e6f68c97 100644 > >--- a/arch/x86/kvm/vmx/tdx.c > >+++ b/arch/x86/kvm/vmx/tdx.c > >@@ -1305,11 +1305,20 @@ static int tdx_handle_ept_violation(struct kvm_vcpu *vcpu) > > } else { > > exit_qual = tdexit_exit_qual(vcpu); > > if (exit_qual & EPT_VIOLATION_ACC_INSTR) { > >+ union tdx_exit_reason exit_reason = to_tdx(vcpu)->exit_reason; > >+ > >+ /* > >+ * Instruction fetch in TD from shared memory > >+ * causes a #PF. > >+ */ > > It is better to hoist this comment above the if-statement. > > /* > * Instruction fetch in TD from shared memory never causes EPT > * violation. Warn if such an EPT violation occurs as the CPU > * probably is buggy. > */ > if (exit_qual & EPT_VIOLATION_ACC_INSTR) { > ... > } > > > but, I am wondering why KVM needs to perform this check. I prefer to drop this > check if KVM doesn't rely on it to handle EPT violation correctly. > > > pr_warn("kvm: TDX instr fetch to shared GPA = 0x%lx @ RIP = 0x%lx\n", > > tdexit_gpa(vcpu), kvm_rip_read(vcpu)); > > how about using vcpu_unimpl()? it is a wrapper for printing such a message. This isn't an "unimplemented" scenario in KVM, this is a "hardware is broken" scenario. Just WARN_ON_ONCE() and move on. Or I suppose since EPT misconfig needs to do something as well: if (KVM_BUG_ON(exit_qual & EPT_VIOLATION_ACC_INSTR, vcpu->kvm)) return -EIO;