[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH 1/7] xen/arm: fix rank calculation in vgic_vcpu_inject_irq
On Tue, 13 Nov 2012, Ian Campbell wrote: > On Tue, 2012-11-13 at 11:57 +0000, Stefano Stabellini wrote: > > On Sat, 27 Oct 2012, Tim Deegan wrote: > > > At 21:47 +0100 on 26 Oct (1351288040), Ian Campbell wrote: > > > > On Fri, 2012-10-26 at 19:42 +0100, Stefano Stabellini wrote: > > > > > I think that the problem is the usage of vgic_irq_rank with registers > > > > > that have 1 bit per interrupt. > > > > > > > > That's very plausible indeed. > > > > > > > > > diff --git a/xen/arch/arm/vgic.c b/xen/arch/arm/vgic.c > > > > > index 3c3983f..92731b6 100644 > > > > > --- a/xen/arch/arm/vgic.c > > > > > +++ b/xen/arch/arm/vgic.c > > > > > @@ -42,13 +42,7 @@ > > > > > */ > > > > > static inline int REG_RANK_NR(int b, uint32_t n) > > > > > { > > > > > - switch ( b ) > > > > > - { > > > > > - case 8: return n >> 3; > > > > > - case 4: return n >> 2; > > > > > - case 2: return n >> 1; > > > > > - default: BUG(); > > > > > - } > > > > > + return n / b; > > > > > > > > All the infrastructure will fall apart if b isn't a power of two, that's > > > > why I used the switch. Can you just add the appropriate case 1 instead? > > > > Probably the bug should be a call to an undefined function to make this > > > > a compile time rather than runtime failure too. > > > > > > BUILD_BUG_ON((b & -b) != b); ? > > > > I can't do that: > > > > error: expression in static assertion is not constant > > I suppose you could make REG_RANK_NR a macro (as it's name implies it > ought to be, oops!). > REG_RANK_NR is called by vgic_irq_rank, so that would need to become a macro too > If not then given that b must be in {1,2,4,8} maybe the switch is > ok/tolerable? If we end up supporting b=16 or 32 then more thought is > probably required around the place anyway. yeah I think is OK _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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