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    SubjectUse virtual cpu accounting if available for guest times.
    Date
    Avi,

    ppc and s390 offer the possibility to track process times precisely
    by looking at cpu timer on every context switch, irq, softirq etc.
    We can use that infrastructure as well for guest time accounting.
    We need to account the used time before we change the state.
    This patch adds a call to account_system_vtime to kvm_guest_enter
    and kvm_guest exit. If CONFIG_VIRT_CPU_ACCOUNTING is not set,
    account_system_vtime is defined in hardirq.h as an empty function,
    which means this patch does not change the behaviour on other
    platforms.

    I compile tested this patch on x86 and function tested the patch on
    s390.

    Avi, please apply.


    Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>

    ---
    drivers/kvm/kvm.h | 3 +++
    1 file changed, 3 insertions(+)

    Index: kvm/drivers/kvm/kvm.h
    ===================================================================
    --- kvm.orig/drivers/kvm/kvm.h
    +++ kvm/drivers/kvm/kvm.h
    @@ -7,6 +7,7 @@
    */

    #include <linux/types.h>
    +#include <linux/hardirq.h>
    #include <linux/list.h>
    #include <linux/mutex.h>
    #include <linux/spinlock.h>
    @@ -669,11 +670,13 @@ __init void kvm_arch_init(void);

    static inline void kvm_guest_enter(void)
    {
    + account_system_vtime(current);
    current->flags |= PF_VCPU;
    }

    static inline void kvm_guest_exit(void)
    {
    + account_system_vtime(current);
    current->flags &= ~PF_VCPU;
    }

    -
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