Re: [PATCH] xen/arm: irq: Initialize the per-CPU IRQs while preparing the CPU

[Stefano Stabellini <sstabellini@kernel.org>]

On Wed, 22 Jun 2022, Julien Grall wrote:
> On 15/06/2022 01:32, Stefano Stabellini wrote:
> > On Tue, 14 Jun 2022, Julien Grall wrote:
> > > From: Julien Grall <jgrall@amazon.com>
> > > 
> > > Commit 5047cd1d5dea "xen/common: Use enhanced ASSERT_ALLOC_CONTEXT in
> > > xmalloc()" extended the checks in _xmalloc() to catch any use of the
> > > helpers from context with interrupts disabled.
> > > 
> > > Unfortunately, the rule is not followed when initializing the per-CPU
> > > IRQs:
> > > 
> > > (XEN) Xen call trace:
> > > (XEN)    [<002389f4>] _xmalloc+0xfc/0x314 (PC)
> > > (XEN)    [<00000000>] 00000000 (LR)
> > > (XEN)    [<0021a7c4>] init_one_irq_desc+0x48/0xd0
> > > (XEN)    [<002807a8>] irq.c#init_local_irq_data+0x48/0xa4
> > > (XEN)    [<00280834>] init_secondary_IRQ+0x10/0x2c
> > > (XEN)    [<00288fa4>] start_secondary+0x194/0x274
> > > (XEN)    [<40010170>] 40010170
> > > (XEN)
> > > (XEN)
> > > (XEN) ****************************************
> > > (XEN) Panic on CPU 2:
> > > (XEN) Assertion '!in_irq() && (local_irq_is_enabled() || num_online_cpus()
> > > <= 1)' failed at common/xmalloc_tlsf.c:601
> > > (XEN) ****************************************
> > > 
> > > This is happening because zalloc_cpumask_var() may allocate memory
> > > if NR_CPUS is > 2 * sizeof(unsigned long).
> > > 
> > > Avoid the problem by allocate the per-CPU IRQs while preparing the
> > > CPU.
> > > 
> > > This also has the benefit to remove a BUG_ON() in the secondary CPU
> > > code.
> > > 
> > > Signed-off-by: Julien Grall <jgrall@amazon.com>
> > > ---
> > >   xen/arch/arm/include/asm/irq.h |  1 -
> > >   xen/arch/arm/irq.c             | 35 +++++++++++++++++++++++++++-------
> > >   xen/arch/arm/smpboot.c         |  2 --
> > >   3 files changed, 28 insertions(+), 10 deletions(-)
> > > 
> > > diff --git a/xen/arch/arm/include/asm/irq.h
> > > b/xen/arch/arm/include/asm/irq.h
> > > index e45d57459899..245f49dcbac5 100644
> > > --- a/xen/arch/arm/include/asm/irq.h
> > > +++ b/xen/arch/arm/include/asm/irq.h
> > > @@ -73,7 +73,6 @@ static inline bool is_lpi(unsigned int irq)
> > >   bool is_assignable_irq(unsigned int irq);
> > >     void init_IRQ(void);
> > > -void init_secondary_IRQ(void);
> > >     int route_irq_to_guest(struct domain *d, unsigned int virq,
> > >                          unsigned int irq, const char *devname);
> > > diff --git a/xen/arch/arm/irq.c b/xen/arch/arm/irq.c
> > > index b761d90c4063..56bdcb95335d 100644
> > > --- a/xen/arch/arm/irq.c
> > > +++ b/xen/arch/arm/irq.c
> > > @@ -17,6 +17,7 @@
> > >    * GNU General Public License for more details.
> > >    */
> > >   +#include <xen/cpu.h>
> > >   #include <xen/lib.h>
> > >   #include <xen/spinlock.h>
> > >   #include <xen/irq.h>
> > > @@ -100,7 +101,7 @@ static int __init init_irq_data(void)
> > >       return 0;
> > >   }
> > >   -static int init_local_irq_data(void)
> > > +static int init_local_irq_data(unsigned int cpu)
> > >   {
> > >       int irq;
> > >   @@ -108,7 +109,7 @@ static int init_local_irq_data(void)
> > >         for ( irq = 0; irq < NR_LOCAL_IRQS; irq++ )
> > >       {
> > > -        struct irq_desc *desc = irq_to_desc(irq);
> > > +        struct irq_desc *desc = &per_cpu(local_irq_desc, cpu)[irq];
> > >           int rc = init_one_irq_desc(desc);
> > >             if ( rc )
> > > @@ -131,6 +132,29 @@ static int init_local_irq_data(void)
> > >       return 0;
> > >   }
> > >   +static int cpu_callback(struct notifier_block *nfb, unsigned long
> > > action,
> > > +                        void *hcpu)
> > > +{
> > > +    unsigned long cpu = (unsigned long)hcpu;
> > 
> > unsigned int cpu ?
> 
> Hmmm... We seem to have a mix in the code base. I am OK to switch to unsigned
> int.
> 
> > 
> > The rest looks good
> Can this be converted to an ack or review tag?

Yes, add my reviewed-by