[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH V6 00/10] Support more than 8 vcpus on arm64 with GICv3
On Fri, 2015-06-05 at 15:37 +0100, Julien Grall wrote: > On 05/06/15 15:08, Ian Campbell wrote: > > On Mon, 2015-06-01 at 20:56 +0800, Chen Baozi wrote: > >> From: Chen Baozi <baozich@xxxxxxxxx> > >> > >> Currently the number of vcpus on arm64 with GICv3 is limited up to 8 due > >> to the fixed size of redistributor mmio region. > > > > Are we talking about only guests here or are hosts impacted too somehow? > > Guest only. The GICv3 driver should already supports 128 CPUs (though > never tested). > > >> Increasing the size > >> makes the number expand to 16 because of AFF0 restriction on GICv3. > > > > Can you give a reference for this please? "AFF0" doesn't appear anywhere > > in my gic v3 spec, and "4.2.2 Interrupt Routing in GICv3 Systems" > > implies 256 processors at each affinity level (which is what I > > expected). > > 5.7.29 ICC_SGI0R_EL1, ICC_SGI1R_EL1 and ICC_ASGI1R_EL1: > > "Note: this restricts distribution of SGIs to the first 16 processors of > an affinity 1 cluster". Thanks, they really buried the lead on that one, the section introducing affinity hierarchy doesn't even hint at this limit! > > Therefore any CPU using AFF0 >= 16 would never receive SGI. > > FWIW, Linux is shouting loud when the AFF0 is too high. Xen does the > same thing in the GICv3 drivers. > > > Regards, > _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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