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([172.25.112.68]) by orsmga002.jf.intel.com with ESMTP; 06 Mar 2023 19:05:23 -0800 From: Xin Li To: linux-kernel@vger.kernel.org, x86@kernel.org, kvm@vger.kernel.org Cc: tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, hpa@zytor.com, peterz@infradead.org, andrew.cooper3@citrix.com, seanjc@google.com, pbonzini@redhat.com, ravi.v.shankar@intel.com Subject: [PATCH v5 34/34] KVM: x86/vmx: execute "int $2" to handle NMI in NMI caused VM exits when FRED is enabled Date: Mon, 6 Mar 2023 18:39:46 -0800 Message-Id: <20230307023946.14516-35-xin3.li@intel.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20230307023946.14516-1-xin3.li@intel.com> References: <20230307023946.14516-1-xin3.li@intel.com> MIME-Version: 1.0 X-Spam-Status: No, score=-4.4 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_MED, SPF_HELO_NONE,SPF_NONE,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: =?utf-8?q?INBOX?= X-GMAIL-THRID: =?utf-8?q?1759676966003658059?= X-GMAIL-MSGID: =?utf-8?q?1759676966003658059?= Execute "int $2" to handle NMI in NMI caused VM exits when FRED is enabled. Like IRET for IDT, ERETS/ERETU are required to end the NMI handler for FRED to unblock NMI ASAP (w/ bit 28 of CS set). And there are 2 approaches to invoke the FRED NMI handler: 1) execute "int $2", let the h/w do the job. 2) create a FRED NMI stack frame on the current kernel stack with ASM, and then jump to fred_entrypoint_kernel in arch/x86/entry/entry_64_fred.S. 1) is preferred as we want less ASM. Tested-by: Shan Kang Signed-off-by: Xin Li --- Changes since v4: *) Do NOT use the term "injection", which in the KVM context means to reinject an event into the guest (Sean Christopherson). *) Add the explanation of why to execute "int $2" to invoke the NMI handler in NMI caused VM exits (Sean Christopherson). --- arch/x86/kvm/vmx/vmx.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c index 3ebeaab34b2e..4f12ead2266b 100644 --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -7229,7 +7229,16 @@ static noinstr void vmx_vcpu_enter_exit(struct kvm_vcpu *vcpu, if ((u16)vmx->exit_reason.basic == EXIT_REASON_EXCEPTION_NMI && is_nmi(vmx_get_intr_info(vcpu))) { kvm_before_interrupt(vcpu, KVM_HANDLING_NMI); - vmx_do_nmi_irqoff(); + /* + * Like IRET for IDT, ERETS/ERETU are required to end the NMI + * handler for FRED to unblock NMI ASAP (w/ bit 28 of CS set). + * + * Invoke the FRED NMI handler through executing "int $2". + */ + if (cpu_feature_enabled(X86_FEATURE_FRED)) + asm volatile("int $2"); + else + vmx_do_nmi_irqoff(); kvm_after_interrupt(vcpu); }