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bh=85FbKOIGeJKFvrZkC+4B4Gx5bHvgxBGU0hkt5+QsJqk=; b=EHi6CD/KDOYL8kMfViFr+rsD1X/LaCYXjAeq6z/n3O5NrAKXvVLgxVRnwvdLnZfW78 h9LZsRYvH6QJwv4lncgjjTVmI/Tk3EJkMbK0v7dDz51kP1Rw0R2OSc6SenCF9KtBOeeK pT0tbAlu0mOUb9rc/jH925fW13B+x3Yj2vSXcLFHKCz+voT6Dmg6ul+72I4ZKghs4z8E 8vxL8zn8lUlPXqivMP4gmSbI7SGRSMhr8xyhPTCeOO47dC3Wgm+wWey5VQ6t/hBoP32a ZlH31tk01ofH5rXkxsvn5LPjvfCG0NskuAggnbs/XBeM1DT7f4fr1K2umixQU7oGaHb6 aAAw== X-Gm-Message-State: AC+VfDyvodnaMuZ2NmRZI5wCTVLXhQaEvET97aBtMc0rZQMmpG/7H0sF zctloVaj/9wIrmcnl7xlEGA= X-Received: by 2002:a17:903:2310:b0:1a6:54ce:4311 with SMTP id d16-20020a170903231000b001a654ce4311mr16387616plh.43.1682931471101; Mon, 01 May 2023 01:57:51 -0700 (PDT) Received: from ubuntu-Virtual-Machine.corp.microsoft.com ([2001:4898:80e8:b:e11b:15ea:ad44:bde7]) by smtp.gmail.com with ESMTPSA id t13-20020a1709028c8d00b001a4fe00a8d4sm17407070plo.90.2023.05.01.01.57.49 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 01 May 2023 01:57:50 -0700 (PDT) From: Tianyu Lan To: luto@kernel.org, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com, seanjc@google.com, pbonzini@redhat.com, jgross@suse.com, tiala@microsoft.com, kirill@shutemov.name, jiangshan.ljs@antgroup.com, peterz@infradead.org, ashish.kalra@amd.com, srutherford@google.com, akpm@linux-foundation.org, anshuman.khandual@arm.com, pawan.kumar.gupta@linux.intel.com, adrian.hunter@intel.com, daniel.sneddon@linux.intel.com, alexander.shishkin@linux.intel.com, sandipan.das@amd.com, ray.huang@amd.com, brijesh.singh@amd.com, michael.roth@amd.com, thomas.lendacky@amd.com, venu.busireddy@oracle.com, sterritt@google.com, tony.luck@intel.com, samitolvanen@google.com, fenghua.yu@intel.com Cc: pangupta@amd.com, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, linux-hyperv@vger.kernel.org, linux-arch@vger.kernel.org Subject: [RFC PATCH V5 15/15] x86/sev: Fix interrupt exit code paths from #HV exception Date: Mon, 1 May 2023 04:57:25 -0400 Message-Id: <20230501085726.544209-16-ltykernel@gmail.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20230501085726.544209-1-ltykernel@gmail.com> References: <20230501085726.544209-1-ltykernel@gmail.com> MIME-Version: 1.0 X-Spam-Status: No, score=-2.1 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,FREEMAIL_FROM, RCVD_IN_DNSWL_NONE,SPF_HELO_NONE,SPF_PASS,T_SCC_BODY_TEXT_LINE 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?1764681749904663073?= X-GMAIL-MSGID: =?utf-8?q?1764681749904663073?= From: Ashish Kalra Add checks in interrupt exit code paths in case of returns to user mode to check if currently executing the #HV handler then don't follow the irqentry_exit_to_user_mode path as that can potentially cause the #HV handler to be preempted and rescheduled on another CPU. Rescheduled #HV handler on another cpu will cause interrupts to be handled on a different cpu than the injected one, causing invalid EOIs and missed/lost guest interrupts and corresponding hangs and/or per-cpu IRQs handled on non-intended cpu. Signed-off-by: Ashish Kalra --- Change since RFC v3: * Add check of hv_handling_events in the do_exc_hv() to avoid nested entry. --- arch/x86/include/asm/idtentry.h | 66 +++++++++++++++++++++++++++++++++ arch/x86/kernel/sev.c | 37 +++++++++++++++++- 2 files changed, 102 insertions(+), 1 deletion(-) diff --git a/arch/x86/include/asm/idtentry.h b/arch/x86/include/asm/idtentry.h index b0f3501b2767..415b7e14c227 100644 --- a/arch/x86/include/asm/idtentry.h +++ b/arch/x86/include/asm/idtentry.h @@ -13,6 +13,10 @@ #include +#ifdef CONFIG_AMD_MEM_ENCRYPT +noinstr void irqentry_exit_hv_cond(struct pt_regs *regs, irqentry_state_t state); +#endif + /** * DECLARE_IDTENTRY - Declare functions for simple IDT entry points * No error code pushed by hardware @@ -176,6 +180,7 @@ __visible noinstr void func(struct pt_regs *regs, unsigned long error_code) #define DECLARE_IDTENTRY_IRQ(vector, func) \ DECLARE_IDTENTRY_ERRORCODE(vector, func) +#ifndef CONFIG_AMD_MEM_ENCRYPT /** * DEFINE_IDTENTRY_IRQ - Emit code for device interrupt IDT entry points * @func: Function name of the entry point @@ -205,6 +210,26 @@ __visible noinstr void func(struct pt_regs *regs, \ } \ \ static noinline void __##func(struct pt_regs *regs, u32 vector) +#else + +#define DEFINE_IDTENTRY_IRQ(func) \ +static void __##func(struct pt_regs *regs, u32 vector); \ + \ +__visible noinstr void func(struct pt_regs *regs, \ + unsigned long error_code) \ +{ \ + irqentry_state_t state = irqentry_enter(regs); \ + u32 vector = (u32)(u8)error_code; \ + \ + instrumentation_begin(); \ + kvm_set_cpu_l1tf_flush_l1d(); \ + run_irq_on_irqstack_cond(__##func, regs, vector); \ + instrumentation_end(); \ + irqentry_exit_hv_cond(regs, state); \ +} \ + \ +static noinline void __##func(struct pt_regs *regs, u32 vector) +#endif /** * DECLARE_IDTENTRY_SYSVEC - Declare functions for system vector entry points @@ -221,6 +246,7 @@ static noinline void __##func(struct pt_regs *regs, u32 vector) #define DECLARE_IDTENTRY_SYSVEC(vector, func) \ DECLARE_IDTENTRY(vector, func) +#ifndef CONFIG_AMD_MEM_ENCRYPT /** * DEFINE_IDTENTRY_SYSVEC - Emit code for system vector IDT entry points * @func: Function name of the entry point @@ -245,6 +271,26 @@ __visible noinstr void func(struct pt_regs *regs) \ } \ \ static noinline void __##func(struct pt_regs *regs) +#else + +#define DEFINE_IDTENTRY_SYSVEC(func) \ +static void __##func(struct pt_regs *regs); \ + \ +__visible noinstr void func(struct pt_regs *regs) \ +{ \ + irqentry_state_t state = irqentry_enter(regs); \ + \ + instrumentation_begin(); \ + kvm_set_cpu_l1tf_flush_l1d(); \ + run_sysvec_on_irqstack_cond(__##func, regs); \ + instrumentation_end(); \ + irqentry_exit_hv_cond(regs, state); \ +} \ + \ +static noinline void __##func(struct pt_regs *regs) +#endif + +#ifndef CONFIG_AMD_MEM_ENCRYPT /** * DEFINE_IDTENTRY_SYSVEC_SIMPLE - Emit code for simple system vector IDT @@ -274,6 +320,26 @@ __visible noinstr void func(struct pt_regs *regs) \ } \ \ static __always_inline void __##func(struct pt_regs *regs) +#else + +#define DEFINE_IDTENTRY_SYSVEC_SIMPLE(func) \ +static __always_inline void __##func(struct pt_regs *regs); \ + \ +__visible noinstr void func(struct pt_regs *regs) \ +{ \ + irqentry_state_t state = irqentry_enter(regs); \ + \ + instrumentation_begin(); \ + __irq_enter_raw(); \ + kvm_set_cpu_l1tf_flush_l1d(); \ + __##func(regs); \ + __irq_exit_raw(); \ + instrumentation_end(); \ + irqentry_exit_hv_cond(regs, state); \ +} \ + \ +static __always_inline void __##func(struct pt_regs *regs) +#endif /** * DECLARE_IDTENTRY_XENCB - Declare functions for XEN HV callback entry point diff --git a/arch/x86/kernel/sev.c b/arch/x86/kernel/sev.c index b6becf158598..69b55075ddfe 100644 --- a/arch/x86/kernel/sev.c +++ b/arch/x86/kernel/sev.c @@ -149,6 +149,10 @@ struct sev_hv_doorbell_page { struct sev_snp_runtime_data { struct sev_hv_doorbell_page hv_doorbell_page; + /* + * Indication that we are currently handling #HV events. + */ + bool hv_handling_events; }; static DEFINE_PER_CPU(struct sev_snp_runtime_data*, snp_runtime_data); @@ -204,6 +208,12 @@ static void do_exc_hv(struct pt_regs *regs) { union hv_pending_events pending_events; + /* Avoid nested entry. */ + if (this_cpu_read(snp_runtime_data)->hv_handling_events) + return; + + this_cpu_read(snp_runtime_data)->hv_handling_events = true; + while (sev_hv_pending()) { pending_events.events = xchg( &sev_snp_current_doorbell_page()->pending_events.events, @@ -218,7 +228,7 @@ static void do_exc_hv(struct pt_regs *regs) #endif if (!pending_events.vector) - return; + goto out; if (pending_events.vector < FIRST_EXTERNAL_VECTOR) { /* Exception vectors */ @@ -238,6 +248,9 @@ static void do_exc_hv(struct pt_regs *regs) common_interrupt(regs, pending_events.vector); } } + +out: + this_cpu_read(snp_runtime_data)->hv_handling_events = false; } static __always_inline bool on_vc_stack(struct pt_regs *regs) @@ -2542,3 +2555,25 @@ static int __init snp_init_platform_device(void) return 0; } device_initcall(snp_init_platform_device); + +noinstr void irqentry_exit_hv_cond(struct pt_regs *regs, irqentry_state_t state) +{ + /* + * Check whether this returns to user mode, if so and if + * we are currently executing the #HV handler then we don't + * want to follow the irqentry_exit_to_user_mode path as + * that can potentially cause the #HV handler to be + * preempted and rescheduled on another CPU. Rescheduled #HV + * handler on another cpu will cause interrupts to be handled + * on a different cpu than the injected one, causing + * invalid EOIs and missed/lost guest interrupts and + * corresponding hangs and/or per-cpu IRQs handled on + * non-intended cpu. + */ + if (user_mode(regs) && + this_cpu_read(snp_runtime_data)->hv_handling_events) + return; + + /* follow normal interrupt return/exit path */ + irqentry_exit(regs, state); +}