[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH 4/7] xen/arm: gic: Use the correct CPU ID
On Tue, 2013-09-10 at 16:42 +0100, Julien Grall wrote: > On 09/09/2013 02:28 PM, Ian Campbell wrote: > > On Fri, 2013-08-30 at 14:30 +0100, Julien Grall wrote: > >> The GIC mapping of CPU interfaces does not necessarily match the logical > >> CPU numbering. > >> > >> When Xen wants to send an SGI to specific CPU, it needs to use the GIC CPU > >> ID. > >> It can be retrieved from ITARGETSR0, in fact when this field is read, the > >> GIC > >> will return a value that corresponds only to the processor reading the > >> register. > >> So Xen can use the PPI 0 to initialize the mapping. > >> > >> Signed-off-by: Julien Grall <julien.grall@xxxxxxxxxx> > >> --- > >> xen/arch/arm/gic.c | 35 ++++++++++++++++++++++++++++------- > >> 1 file changed, 28 insertions(+), 7 deletions(-) > >> > >> diff --git a/xen/arch/arm/gic.c b/xen/arch/arm/gic.c > >> index cadc258..4f3a8a5 100644 > >> --- a/xen/arch/arm/gic.c > >> +++ b/xen/arch/arm/gic.c > >> @@ -57,6 +57,27 @@ static DEFINE_PER_CPU(uint64_t, lr_mask); > >> > >> static unsigned nr_lrs; > >> > >> +/* The GIC mapping of CPU interfaces does not necessarily match the > >> + * logical CPU numbering. Let's use mapping as returned by the GIC > >> + * itself > >> + */ > >> +#define NR_GIC_CPU_IF 8 > >> +static u8 gic_cpu_map[NR_GIC_CPU_IF] __read_mostly = {0xff}; > > > > Isn't this mapping from logical cpus ids to gic cpus ids? IOW the size > > of this array is the wrong way around? > > This array maps a logical cpu id (the index) to a gic cpus id. The size > if correct, because Xen will allocate logical cpu id from 0 to 7. Oh right, yes. I think NR_CPUS (which should be 8 given the other limitations) is the right size for this array. > > > Is what you want here is a per-cpu variable? > > Does per-cpu variable allow any cpu to retrieve data of another cpu? I > didn't find a such function. per_cpu(variable, cpu) will do it. > > >> + > >> +static unsigned int gic_cpu_mask(const cpumask_t *cpumask) > >> +{ > >> + unsigned int cpu; > >> + unsigned int mask = 0; > >> + > >> + for_each_cpu(cpu, cpumask) > >> + { > >> + ASSERT(cpu < NR_GIC_CPU_IF); > >> + mask |= gic_cpu_map[cpu]; > > > > Further to above, can't cpu here be e.g. 0x100 for an a7 on a big.ITTLE > > system? > > 0x100 is the hardware CPU id. Xen will allocate a logical cpu id from 0. Right. _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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