Re: [Xen-devel] [PATCH] xen: Support 64-bit PV guest receiving NMIs

[Ben Guthro <Benjamin.Guthro@xxxxxxxxxx>]

On 07/19/2013 11:51 AM, Konrad Rzeszutek Wilk wrote:
> Zhenzhong Duan sent a patch that adds some of this functionality
> but this code adds the remaining pieces. The kernel has the
> logic to handle Xen-type-exceptions using the paravirt interface
> in the assembler code (see PARAVIRT_ADJUST_EXCEPTION_FRAME -
> pv_irq_ops.adjust_exception_frame and and INTERRUPT_RETURN -
> pv_cpu_ops.iret).
> 
> That means the nmi handler (and other exception handlers) use
> the hypervisor iret.
> 
> The other changes that would be neccessary for this would
> be to translate the NMI_VECTOR to one of the entries on the
> ipi_vector and make xen_send_IPI_mask_allbutself use different
> events.
> 
> Fortunately for us commit 1db01b4903639fcfaec213701a494fe3fb2c490b
> (xen: Clean up apic ipi interface) implemented this and we piggyback
> on the cleanup such that the apic IPI interface will pass the right
> vector value for NMI.
> 
> With this patch we can trigger NMIs within a PV guest (only tested
> x86_64).
> 
> SysRq : Show backtrace of all active CPUs
> sending NMI to all CPUs:
> NMI backtrace for cpu 2
> CPU 2
> RIP: e030:[<ffffffff8100130a>]  [<ffffffff8100130a>] 
> xen_hypercall_vcpu_op+0xa/0x20
> . snip..
> Call Trace:
>  [<ffffffff813afdc0>] ? xen_send_IPI_one+0x40/0x60
>  [<ffffffff8104bdcb>] __xen_send_IPI_mask+0x2b/0x50
>  [<ffffffff8104c6f9>] xen_send_IPI_all+0x79/0xa0
>  [<ffffffff81074df9>] arch_trigger_all_cpu_backtrace+0x59/0xa0
>  [<ffffffff813d16f9>] sysrq_handle_showallcpus+0x9/0x10
>  [<ffffffff813d1ad9>] __handle_sysrq+0x129/0x190
>  [<ffffffff813d1b40>] ? __handle_sysrq+0x190/0x190
>  [<ffffffff813d1ba4>] write_sysrq_trigger+0x64/0x70
>  [<ffffffff8121211b>] proc_reg_write+0x8b/0xe0
>  [<ffffffff811aa1c4>] vfs_write+0xb4/0x130
>  [<ffffffff811aa98a>] sys_write+0x5a/0xa0
>  [<ffffffff816825e9>] system_call_fastpath+0x16/0x1b
> NMI backtrace for cpu 0
> CPU 0
> . snip..
> Call Trace:
>  [<ffffffff81044180>] ? xen_safe_halt+0x10/0x20
>  [<ffffffff8105746c>] default_idle+0x3c/0x130
>  [<ffffffff81056cf9>] cpu_idle+0x99/0xe0
>  [<ffffffff816619da>] rest_init+0x8a/0xa0
>  [<ffffffff81ac10a4>] start_kernel+0x3da/0x3e7
>  [<ffffffff81ac0ae8>] ? repair_env_string+0x5b/0x5b
>  [<ffffffff81ac05f7>] x86_64_start_reservations+0x2a/0x2c
>  [<ffffffff81ac30ce>] xen_start_kernel+0x56e/0x570
> NMI backtrace for cpu 1
> CPU 1
> RIP: e030:[<ffffffff810013aa>]  [<ffffffff810013aa>] 
> xen_hypercall_sched_op+0xa/0x20
> .snip..
> Call Trace:
>  [<ffffffff81044180>] ? xen_safe_halt+0x10/0x20
>  [<ffffffff8105746c>] default_idle+0x3c/0x130
>  [<ffffffff81056cf9>] cpu_idle+0x99/0xe0
>  [<ffffffff81044969>] ? xen_irq_enable_direct_reloc+0x4/0x4
>  [<ffffffff8166801b>] cpu_bringup_and_idle+0xe/0x10
> NMI backtrace for cpu 3
> CPU 3
> .snip..
> Call Trace:
>  [<ffffffff81044180>] ? xen_safe_halt+0x10/0x20
>  [<ffffffff8105746c>] default_idle+0x3c/0x130
>  [<ffffffff81056cf9>] cpu_idle+0x99/0xe0
>  [<ffffffff81044969>] ? xen_irq_enable_direct_reloc+0x4/0x4
>  [<ffffffff8166801b>] cpu_bringup_and_idle+0xe/0x10
> 
> Incidentally that means kgdb will also now work within
> a PV guest without using the 'nokgdbroundup' workaround.
> 
> Note that the 32-bit version is different and this patch
> does not enable that.
> 
> CC: Lisa Nguyen <lisa@xxxxxxxxxxxxxxx>
> CC: Ben Guthro <benjamin.guthro@xxxxxxxxxx>
> CC: Zhenzhong Duan <zhenzhong.duan@xxxxxxxxxx>
> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>

Looks good to me.


Reviewed-by: Ben Guthro <benjamin.guthro@xxxxxxxxxx>

> ---
>  arch/x86/include/asm/xen/events.h |    1 +
>  arch/x86/xen/enlighten.c          |   13 ++++++++-----
>  arch/x86/xen/setup.c              |   13 +++++++++++--
>  arch/x86/xen/smp.c                |    5 +++++
>  drivers/xen/events.c              |   11 +++++++++++
>  include/xen/interface/vcpu.h      |    2 ++
>  6 files changed, 38 insertions(+), 7 deletions(-)
> 
> diff --git a/arch/x86/include/asm/xen/events.h 
> b/arch/x86/include/asm/xen/events.h
> index ca842f2..608a79d 100644
> --- a/arch/x86/include/asm/xen/events.h
> +++ b/arch/x86/include/asm/xen/events.h
> @@ -7,6 +7,7 @@ enum ipi_vector {
>       XEN_CALL_FUNCTION_SINGLE_VECTOR,
>       XEN_SPIN_UNLOCK_VECTOR,
>       XEN_IRQ_WORK_VECTOR,
> +     XEN_NMI_VECTOR,
>  
>       XEN_NR_IPIS,
>  };
> diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
> index 2fa02bc..231382a 100644
> --- a/arch/x86/xen/enlighten.c
> +++ b/arch/x86/xen/enlighten.c
> @@ -427,8 +427,7 @@ static void __init xen_init_cpuid_mask(void)
>  
>       if (!xen_initial_domain())
>               cpuid_leaf1_edx_mask &=
> -                     ~((1 << X86_FEATURE_APIC) |  /* disable local APIC */
> -                       (1 << X86_FEATURE_ACPI));  /* disable ACPI */
> +                     ~((1 << X86_FEATURE_ACPI));  /* disable ACPI */
>  
>       cpuid_leaf1_ecx_mask &= ~(1 << (X86_FEATURE_X2APIC % 32));
>  
> @@ -735,8 +734,7 @@ static int cvt_gate_to_trap(int vector, const gate_desc 
> *val,
>               addr = (unsigned long)xen_int3;
>       else if (addr == (unsigned long)stack_segment)
>               addr = (unsigned long)xen_stack_segment;
> -     else if (addr == (unsigned long)double_fault ||
> -              addr == (unsigned long)nmi) {
> +     else if (addr == (unsigned long)double_fault) {
>               /* Don't need to handle these */
>               return 0;
>  #ifdef CONFIG_X86_MCE
> @@ -747,7 +745,12 @@ static int cvt_gate_to_trap(int vector, const gate_desc 
> *val,
>                */
>               ;
>  #endif
> -     } else {
> +     } else if (addr == (unsigned long)nmi)
> +             /*
> +              * Use the native version as well.
> +              */
> +             ;
> +     else {
>               /* Some other trap using IST? */
>               if (WARN_ON(val->ist != 0))
>                       return 0;
> diff --git a/arch/x86/xen/setup.c b/arch/x86/xen/setup.c
> index 94eac5c..f78877c 100644
> --- a/arch/x86/xen/setup.c
> +++ b/arch/x86/xen/setup.c
> @@ -33,6 +33,9 @@
>  /* These are code, but not functions.  Defined in entry.S */
>  extern const char xen_hypervisor_callback[];
>  extern const char xen_failsafe_callback[];
> +#ifdef CONFIG_X86_64
> +extern const char nmi[];
> +#endif
>  extern void xen_sysenter_target(void);
>  extern void xen_syscall_target(void);
>  extern void xen_syscall32_target(void);
> @@ -525,7 +528,13 @@ void __cpuinit xen_enable_syscall(void)
>       }
>  #endif /* CONFIG_X86_64 */
>  }
> -
> +void __cpuinit xen_enable_nmi(void)
> +{
> +#ifdef CONFIG_X86_64
> +     if (register_callback(CALLBACKTYPE_nmi, nmi))
> +             BUG();
> +#endif
> +}
>  void __init xen_arch_setup(void)
>  {
>       xen_panic_handler_init();
> @@ -543,7 +552,7 @@ void __init xen_arch_setup(void)
>  
>       xen_enable_sysenter();
>       xen_enable_syscall();
> -
> +     xen_enable_nmi();
>  #ifdef CONFIG_ACPI
>       if (!(xen_start_info->flags & SIF_INITDOMAIN)) {
>               printk(KERN_INFO "ACPI in unprivileged domain disabled\n");
> diff --git a/arch/x86/xen/smp.c b/arch/x86/xen/smp.c
> index c1367b2..d792cce 100644
> --- a/arch/x86/xen/smp.c
> +++ b/arch/x86/xen/smp.c
> @@ -572,6 +572,10 @@ static inline int xen_map_vector(int vector)
>       case IRQ_WORK_VECTOR:
>               xen_vector = XEN_IRQ_WORK_VECTOR;
>               break;
> +     case NMI_VECTOR:
> +     case APIC_DM_NMI:
> +             xen_vector = XEN_NMI_VECTOR;
> +             break;
>       default:
>               xen_vector = -1;
>               printk(KERN_ERR "xen: vector 0x%x is not implemented\n",
> @@ -659,6 +663,7 @@ static irqreturn_t xen_irq_work_interrupt(int irq, void 
> *dev_id)
>       return IRQ_HANDLED;
>  }
>  
> +
>  static const struct smp_ops xen_smp_ops __initconst = {
>       .smp_prepare_boot_cpu = xen_smp_prepare_boot_cpu,
>       .smp_prepare_cpus = xen_smp_prepare_cpus,
> diff --git a/drivers/xen/events.c b/drivers/xen/events.c
> index a58ac43..419cc44 100644
> --- a/drivers/xen/events.c
> +++ b/drivers/xen/events.c
> @@ -56,6 +56,7 @@
>  #include <xen/interface/hvm/params.h>
>  #include <xen/interface/physdev.h>
>  #include <xen/interface/sched.h>
> +#include <xen/interface/vcpu.h>
>  #include <asm/hw_irq.h>
>  
>  /*
> @@ -1213,6 +1214,16 @@ EXPORT_SYMBOL_GPL(evtchn_put);
>  void xen_send_IPI_one(unsigned int cpu, enum ipi_vector vector)
>  {
>       int irq = per_cpu(ipi_to_irq, cpu)[vector];
> +
> +     /*
> +      * In which the IRQ will be -1.
> +      */
> +     if (unlikely(vector == XEN_NMI_VECTOR)) {
> +             int rc =  HYPERVISOR_vcpu_op(VCPUOP_send_nmi, cpu, NULL);
> +             if (rc < 0)
> +                     printk(KERN_WARNING "Sending nmi to CPU%d failed 
> (rc:%d)\n", cpu, rc);
> +             return;
> +     }
>       BUG_ON(irq < 0);
>       notify_remote_via_irq(irq);
>  }
> diff --git a/include/xen/interface/vcpu.h b/include/xen/interface/vcpu.h
> index 87e6f8a..b05288c 100644
> --- a/include/xen/interface/vcpu.h
> +++ b/include/xen/interface/vcpu.h
> @@ -170,4 +170,6 @@ struct vcpu_register_vcpu_info {
>  };
>  DEFINE_GUEST_HANDLE_STRUCT(vcpu_register_vcpu_info);
>  
> +/* Send an NMI to the specified VCPU. @extra_arg == NULL. */
> +#define VCPUOP_send_nmi             11
>  #endif /* __XEN_PUBLIC_VCPU_H__ */
> 

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