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    SubjectRE: [patch V3 43/44] x86/idt: Simplify alloc_intr_gate
    Date


    > -----Original Message-----
    > From: Thomas Gleixner [mailto:tglx@linutronix.de]
    > Sent: Sunday, August 27, 2017 11:48 PM
    > To: LKML <linux-kernel@vger.kernel.org>
    > Cc: Ingo Molnar <mingo@kernel.org>; Peter Anvin <hpa@zytor.com>; Peter
    > Zijlstra <peterz@infradead.org>; Andy Lutomirski <luto@kernel.org>;
    > Borislav Petkov <bp@alien8.de>; Steven Rostedt <rostedt@goodmis.org>;
    > Juergen Gross <jgross@suse.com>; KY Srinivasan <kys@microsoft.com>;
    > Stephen Hemminger <sthemmin@microsoft.com>; Boris Ostrovsky
    > <boris.ostrovsky@oracle.com>
    > Subject: [patch V3 43/44] x86/idt: Simplify alloc_intr_gate
    >
    > The only users of alloc_intr_gate() are hypervisors, which both check the
    > used_vectors bitmap whether they have allocated the gate already. Move
    > that
    > check into alloc_intr_gate() and simplify the users.
    >
    > Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
    > Reviewed-by: Juergen Gross <jgross@suse.com>
    > Cc: "K. Y. Srinivasan" <kys@microsoft.com>

    Reviewed-by: K. Y. Srinivasan <kys@microsoft.com>

    > Cc: Stephen Hemminger <sthemmin@microsoft.com>
    > Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
    > Cc: Juergen Gross <jgross@suse.com>
    > ---
    > arch/x86/kernel/cpu/mshyperv.c | 9 ++-------
    > arch/x86/kernel/idt.c | 6 +++---
    > drivers/xen/events/events_base.c | 6 ++----
    > 3 files changed, 7 insertions(+), 14 deletions(-)
    >
    > --- a/arch/x86/kernel/cpu/mshyperv.c
    > +++ b/arch/x86/kernel/cpu/mshyperv.c
    > @@ -59,13 +59,8 @@ void hyperv_vector_handler(struct pt_reg
    > void hv_setup_vmbus_irq(void (*handler)(void))
    > {
    > vmbus_handler = handler;
    > - /*
    > - * Setup the IDT for hypervisor callback. Prevent reallocation
    > - * at module reload.
    > - */
    > - if (!test_bit(HYPERVISOR_CALLBACK_VECTOR, used_vectors))
    > - alloc_intr_gate(HYPERVISOR_CALLBACK_VECTOR,
    > - hyperv_callback_vector);
    > + /* Setup the IDT for hypervisor callback */
    > + alloc_intr_gate(HYPERVISOR_CALLBACK_VECTOR,
    > hyperv_callback_vector);
    > }
    >
    > void hv_remove_vmbus_irq(void)
    > --- a/arch/x86/kernel/idt.c
    > +++ b/arch/x86/kernel/idt.c
    > @@ -354,7 +354,7 @@ void set_intr_gate(unsigned int n, const
    >
    > void alloc_intr_gate(unsigned int n, const void *addr)
    > {
    > - BUG_ON(test_bit(n, used_vectors) || n < FIRST_SYSTEM_VECTOR);
    > - set_bit(n, used_vectors);
    > - set_intr_gate(n, addr);
    > + BUG_ON(n < FIRST_SYSTEM_VECTOR);
    > + if (!test_and_set_bit(n, used_vectors))
    > + set_intr_gate(n, addr);
    > }
    > --- a/drivers/xen/events/events_base.c
    > +++ b/drivers/xen/events/events_base.c
    > @@ -1653,10 +1653,8 @@ void xen_callback_vector(void)
    > return;
    > }
    > pr_info("Xen HVM callback vector for event delivery is
    > enabled\n");
    > - /* in the restore case the vector has already been allocated
    > */
    > - if (!test_bit(HYPERVISOR_CALLBACK_VECTOR,
    > used_vectors))
    > - alloc_intr_gate(HYPERVISOR_CALLBACK_VECTOR,
    > - xen_hvm_callback_vector);
    > + alloc_intr_gate(HYPERVISOR_CALLBACK_VECTOR,
    > + xen_hvm_callback_vector);
    > }
    > }
    > #else
    >

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