[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH RFC 3/9] console: add EHCI debug port based serial console
>>> On 30.07.12 at 22:51, Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx> wrote: >> + set_fixmap_nocache(FIX_EHCI_DBGP, dbgp->bar_val); > > Should this have dbgp->bar_val & PAGE_MASK ? No, the set_fixmap_nocache() implementation shifts out the low bits. >> + case PHYSDEVOP_DBGP_RESET_PREPARE: > > Oh, you have a handoff protocol! > > So how does this work without using this? Meaning if one uses Xen hypervisor > EHCI with a pvops kernel that does not implement this? The hypervisor will lose access to its console (and the next console access will cause a brief hang that does no other harm). That's the same behavior as for native Linux if you ripped out the handoff protocol (and the effect is even specified that way by the specification). Plus - no-one is required to use the new functionality when (s)he's aware that Dom0 doesn't cope. >> + return ehci_dbgp_external_startup(&ehci_dbgp) ?: 1; > > Oh, this is new. With the ?: it just passes on the return value from > ehci_dbgp_external_startup? Yes, but it's not new. Just grep for the construct in Xen or Linux - it's being used in a number of places, and has been supported by gcc virtually forever. Jan _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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