From: Juergen Gross <jgross@suse.com> To: xen-devel@lists.xenproject.org, x86@kernel.org, linux-kernel@vger.kernel.org Cc: Juergen Gross <jgross@suse.com>, Boris Ostrovsky <boris.ostrovsky@oracle.com>, Stefano Stabellini <sstabellini@kernel.org>, Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>, "H. Peter Anvin" <hpa@zytor.com> Subject: [PATCH] x86/xen: disable nosmt in Xen guests Date: Wed, 12 Jun 2019 12:12:28 +0200 [thread overview] Message-ID: <20190612101228.23898-1-jgross@suse.com> (raw) When running as a Xen guest selecting "nosmt" either via command line or implicitly via default settings makes no sense, as the guest has no clue about the real system topology it is running on. With Xen it is the hypervisor's job to ensure the proper bug mitigations are active regarding smt settings. So when running as a Xen guest set cpu_smt_control to "not supported" in order to avoid disabling random vcpus. Signed-off-by: Juergen Gross <jgross@suse.com> --- arch/x86/xen/enlighten.c | 8 ++++++++ arch/x86/xen/enlighten_hvm.c | 2 ++ arch/x86/xen/enlighten_pv.c | 2 ++ arch/x86/xen/xen-ops.h | 2 ++ 4 files changed, 14 insertions(+) diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c index 750f46ad018a..312b73698d0c 100644 --- a/arch/x86/xen/enlighten.c +++ b/arch/x86/xen/enlighten.c @@ -345,3 +345,11 @@ void xen_arch_unregister_cpu(int num) } EXPORT_SYMBOL(xen_arch_unregister_cpu); #endif + +void __init xen_disable_nosmt(void) +{ +#ifdef CONFIG_HOTPLUG_SMT + /* Don't allow SMT disabling in Xen guests. */ + cpu_smt_control = CPU_SMT_NOT_SUPPORTED; +#endif +} diff --git a/arch/x86/xen/enlighten_hvm.c b/arch/x86/xen/enlighten_hvm.c index 0e75642d42a3..7c62662cd2ca 100644 --- a/arch/x86/xen/enlighten_hvm.c +++ b/arch/x86/xen/enlighten_hvm.c @@ -116,6 +116,8 @@ static void __init init_hvm_pv_info(void) this_cpu_write(xen_vcpu_id, ebx); else this_cpu_write(xen_vcpu_id, smp_processor_id()); + + xen_disable_nosmt(); } #ifdef CONFIG_KEXEC_CORE diff --git a/arch/x86/xen/enlighten_pv.c b/arch/x86/xen/enlighten_pv.c index 4722ba2966ac..dcfec65bca60 100644 --- a/arch/x86/xen/enlighten_pv.c +++ b/arch/x86/xen/enlighten_pv.c @@ -131,6 +131,8 @@ static void __init xen_pv_init_platform(void) /* pvclock is in shared info area */ xen_init_time_ops(); + + xen_disable_nosmt(); } static void __init xen_pv_guest_late_init(void) diff --git a/arch/x86/xen/xen-ops.h b/arch/x86/xen/xen-ops.h index 2f111f47ba98..63a31b9d7217 100644 --- a/arch/x86/xen/xen-ops.h +++ b/arch/x86/xen/xen-ops.h @@ -161,4 +161,6 @@ void xen_hvm_post_suspend(int suspend_cancelled); static inline void xen_hvm_post_suspend(int suspend_cancelled) {} #endif +void __init xen_disable_nosmt(void); + #endif /* XEN_OPS_H */ -- 2.16.4
WARNING: multiple messages have this Message-ID (diff)
From: Juergen Gross <jgross@suse.com> To: xen-devel@lists.xenproject.org, x86@kernel.org, linux-kernel@vger.kernel.org Cc: Juergen Gross <jgross@suse.com>, Stefano Stabellini <sstabellini@kernel.org>, Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>, "H. Peter Anvin" <hpa@zytor.com>, Boris Ostrovsky <boris.ostrovsky@oracle.com>, Thomas Gleixner <tglx@linutronix.de> Subject: [Xen-devel] [PATCH] x86/xen: disable nosmt in Xen guests Date: Wed, 12 Jun 2019 12:12:28 +0200 [thread overview] Message-ID: <20190612101228.23898-1-jgross@suse.com> (raw) When running as a Xen guest selecting "nosmt" either via command line or implicitly via default settings makes no sense, as the guest has no clue about the real system topology it is running on. With Xen it is the hypervisor's job to ensure the proper bug mitigations are active regarding smt settings. So when running as a Xen guest set cpu_smt_control to "not supported" in order to avoid disabling random vcpus. Signed-off-by: Juergen Gross <jgross@suse.com> --- arch/x86/xen/enlighten.c | 8 ++++++++ arch/x86/xen/enlighten_hvm.c | 2 ++ arch/x86/xen/enlighten_pv.c | 2 ++ arch/x86/xen/xen-ops.h | 2 ++ 4 files changed, 14 insertions(+) diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c index 750f46ad018a..312b73698d0c 100644 --- a/arch/x86/xen/enlighten.c +++ b/arch/x86/xen/enlighten.c @@ -345,3 +345,11 @@ void xen_arch_unregister_cpu(int num) } EXPORT_SYMBOL(xen_arch_unregister_cpu); #endif + +void __init xen_disable_nosmt(void) +{ +#ifdef CONFIG_HOTPLUG_SMT + /* Don't allow SMT disabling in Xen guests. */ + cpu_smt_control = CPU_SMT_NOT_SUPPORTED; +#endif +} diff --git a/arch/x86/xen/enlighten_hvm.c b/arch/x86/xen/enlighten_hvm.c index 0e75642d42a3..7c62662cd2ca 100644 --- a/arch/x86/xen/enlighten_hvm.c +++ b/arch/x86/xen/enlighten_hvm.c @@ -116,6 +116,8 @@ static void __init init_hvm_pv_info(void) this_cpu_write(xen_vcpu_id, ebx); else this_cpu_write(xen_vcpu_id, smp_processor_id()); + + xen_disable_nosmt(); } #ifdef CONFIG_KEXEC_CORE diff --git a/arch/x86/xen/enlighten_pv.c b/arch/x86/xen/enlighten_pv.c index 4722ba2966ac..dcfec65bca60 100644 --- a/arch/x86/xen/enlighten_pv.c +++ b/arch/x86/xen/enlighten_pv.c @@ -131,6 +131,8 @@ static void __init xen_pv_init_platform(void) /* pvclock is in shared info area */ xen_init_time_ops(); + + xen_disable_nosmt(); } static void __init xen_pv_guest_late_init(void) diff --git a/arch/x86/xen/xen-ops.h b/arch/x86/xen/xen-ops.h index 2f111f47ba98..63a31b9d7217 100644 --- a/arch/x86/xen/xen-ops.h +++ b/arch/x86/xen/xen-ops.h @@ -161,4 +161,6 @@ void xen_hvm_post_suspend(int suspend_cancelled); static inline void xen_hvm_post_suspend(int suspend_cancelled) {} #endif +void __init xen_disable_nosmt(void); + #endif /* XEN_OPS_H */ -- 2.16.4 _______________________________________________ Xen-devel mailing list Xen-devel@lists.xenproject.org https://lists.xenproject.org/mailman/listinfo/xen-devel
next reply other threads:[~2019-06-12 10:12 UTC|newest] Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top 2019-06-12 10:12 Juergen Gross [this message] 2019-06-12 10:12 ` [Xen-devel] [PATCH] x86/xen: disable nosmt in Xen guests Juergen Gross 2019-06-12 10:19 ` Jan Beulich 2019-06-12 10:19 ` Jan Beulich 2019-06-12 10:36 ` Juergen Gross 2019-06-12 10:36 ` Juergen Gross 2019-06-12 11:48 ` Peter Zijlstra 2019-06-12 11:48 ` [Xen-devel] " Peter Zijlstra 2019-06-12 14:59 ` Juergen Gross 2019-06-12 14:59 ` [Xen-devel] " Juergen Gross
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