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Re: [Xen-devel] [PATCH v5 2/6] virt, sched: add generic vcpu pinning support



On 06/04/16 16:17, Juergen Gross wrote:
Add generic virtualization support for pinning the current vcpu to a
specified physical cpu. As this operation isn't performance critical
(a very limited set of operations like BIOS calls and SMIs is expected
to need this) just add a hypervisor specific indirection.

Signed-off-by: Juergen Gross <jgross@xxxxxxxx>

Could please some maintainer comment on this patch?


Juergen

---
V4: move this patch some places up in the series
     WARN_ONCE in case platform doesn't support pinning as requested by
     Peter Zijlstra

V3: use getc_cpu()/put_cpu() as suggested by David Vrabel

V2: adapt to using workqueues
     add include/linux/hypervisor.h to hide architecture specific stuff
     from generic kernel code

In case paravirt maintainers don't want to be responsible for
include/linux/hypervisor.h I could take it.
---
  MAINTAINERS                       |  1 +
  arch/x86/include/asm/hypervisor.h |  4 ++++
  arch/x86/kernel/cpu/hypervisor.c  | 11 +++++++++++
  include/linux/hypervisor.h        | 17 +++++++++++++++++
  kernel/smp.c                      |  1 +
  kernel/up.c                       |  1 +
  6 files changed, 35 insertions(+)
  create mode 100644 include/linux/hypervisor.h

diff --git a/MAINTAINERS b/MAINTAINERS
index 40eb1db..d3bde4f 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -8330,6 +8330,7 @@ S:        Supported
  F:    Documentation/virtual/paravirt_ops.txt
  F:    arch/*/kernel/paravirt*
  F:    arch/*/include/asm/paravirt.h
+F:     include/linux/hypervisor.h

  PARIDE DRIVERS FOR PARALLEL PORT IDE DEVICES
  M:    Tim Waugh <tim@xxxxxxxxxxxx>
diff --git a/arch/x86/include/asm/hypervisor.h 
b/arch/x86/include/asm/hypervisor.h
index 055ea99..67942b6 100644
--- a/arch/x86/include/asm/hypervisor.h
+++ b/arch/x86/include/asm/hypervisor.h
@@ -43,6 +43,9 @@ struct hypervisor_x86 {

        /* X2APIC detection (run once per boot) */
        bool            (*x2apic_available)(void);
+
+       /* pin current vcpu to specified physical cpu (run rarely) */
+       void            (*pin_vcpu)(int);
  };

  extern const struct hypervisor_x86 *x86_hyper;
@@ -56,6 +59,7 @@ extern const struct hypervisor_x86 x86_hyper_kvm;
  extern void init_hypervisor(struct cpuinfo_x86 *c);
  extern void init_hypervisor_platform(void);
  extern bool hypervisor_x2apic_available(void);
+extern void hypervisor_pin_vcpu(int cpu);
  #else
  static inline void init_hypervisor(struct cpuinfo_x86 *c) { }
  static inline void init_hypervisor_platform(void) { }
diff --git a/arch/x86/kernel/cpu/hypervisor.c b/arch/x86/kernel/cpu/hypervisor.c
index 73d391a..ff108f8 100644
--- a/arch/x86/kernel/cpu/hypervisor.c
+++ b/arch/x86/kernel/cpu/hypervisor.c
@@ -85,3 +85,14 @@ bool __init hypervisor_x2apic_available(void)
               x86_hyper->x2apic_available &&
               x86_hyper->x2apic_available();
  }
+
+void hypervisor_pin_vcpu(int cpu)
+{
+       if (!x86_hyper)
+               return;
+
+       if (x86_hyper->pin_vcpu)
+               x86_hyper->pin_vcpu(cpu);
+       else
+               WARN_ONCE(1, "vcpu pinning requested but not supported!\n");
+}
diff --git a/include/linux/hypervisor.h b/include/linux/hypervisor.h
new file mode 100644
index 0000000..3fa5ef2
--- /dev/null
+++ b/include/linux/hypervisor.h
@@ -0,0 +1,17 @@
+#ifndef __LINUX_HYPEVISOR_H
+#define __LINUX_HYPEVISOR_H
+
+/*
+ *     Generic Hypervisor support
+ *             Juergen Gross <jgross@xxxxxxxx>
+ */
+
+#ifdef CONFIG_HYPERVISOR_GUEST
+#include <asm/hypervisor.h>
+#else
+static inline void hypervisor_pin_vcpu(int cpu)
+{
+}
+#endif
+
+#endif /* __LINUX_HYPEVISOR_H */
diff --git a/kernel/smp.c b/kernel/smp.c
index 7416544..9388064 100644
--- a/kernel/smp.c
+++ b/kernel/smp.c
@@ -14,6 +14,7 @@
  #include <linux/smp.h>
  #include <linux/cpu.h>
  #include <linux/sched.h>
+#include <linux/hypervisor.h>

  #include "smpboot.h"

diff --git a/kernel/up.c b/kernel/up.c
index 1760bf3..3ccee2b 100644
--- a/kernel/up.c
+++ b/kernel/up.c
@@ -6,6 +6,7 @@
  #include <linux/kernel.h>
  #include <linux/export.h>
  #include <linux/smp.h>
+#include <linux/hypervisor.h>

  int smp_call_function_single(int cpu, void (*func) (void *info), void *info,
                                int wait)



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