Messages in this thread | | | Date | Tue, 24 Apr 2012 12:23:22 -0400 | From | Konrad Rzeszutek Wilk <> | Subject | Re: [Xen-devel] [PATCH] xen/apic: implement io apic read with hypercall |
| |
On Tue, Apr 24, 2012 at 10:43:53PM +0800, Lin Ming wrote: > On Mon, Apr 23, 2012 at 11:11 PM, Konrad Rzeszutek Wilk > <konrad.wilk@oracle.com> wrote: > >> >> > How about return -1 on error? > >> >> > The calling function can check -1 for error. > >> >> > >> >> Isn't -1 potentially (at least theoretically) a valid value to read from > >> >> one of these registers? > >> > > >> > Yeah, but then we are back to crashing at bootup (with dom0) :-) > >> > > >> > Perhaps the fallback is to emulate (so retain some of the original code) > >> > as we have been since .. uh 3.0? > >> > >> Do you mean the return value of io_apic_read in 3.0? > > > > No. I meant that we would continue to emulate. The improvement > > is that now we do: > > > > if (reg == 0x1) > > return 0x00170020; > > else if (reg == 0x0) > > return apic << 24; > > > > instead of 0xfdfdfdfd. > > > >> It's 0xffffffff. > > > > Now it is 0xfdfdfdfd. > > > > I am suggesting that instead of BUG_ON(), we fallback to do returning > > an emulatated IO_APIC values - like the ones that this original patch > > cooked up.. > > But we still need to return some value if the register is not emulated.
Right. 0xfd; > > How about below?
Almost perfect. > > unsigned int xen_io_apic_read(unsigned apic, unsigned reg) > { > struct physdev_apic apic_op; > int ret; > > apic_op.apic_physbase = mpc_ioapic_addr(apic); > apic_op.reg = reg; > ret = HYPERVISOR_physdev_op(PHYSDEVOP_apic_read, &apic_op); > if (!ret) > return apic_op.value; > > /* emulate register */ > if (reg == 0x1) > return 0x00170020; > else if (reg == 0x0) > return apic << 24; > else > return -1;
return 0xfd; > } -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |