[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH 2 of 5] rombios/ata: Do not wait for BSY to be set
O> SEABios has explicitly removed the wait for the BSY bit to be set. We > want to remove it because Qemu will not set the BSY bit, resulting in So why not fix the qemu emulation bug ? > 42k needless polled IO traps while we wait for the timeout (which is, if > I remember correctly, based on a loop counter rather than any notion of > actual time) Not good, although half caused by the fact that years on qemu still hasn't implemented predictors to avoid trapping further than the kernel layer 8) > We can certainly argue about the outb(0x80,0x00). When I was comparing > ROMBios with SEABios, this outb was the closest I could easily get to a > udelay(5) without implement udelay() in ROMBios. Xen will execute an > outb(0x80, 0x00) on the real hardware if a guest executes it; Don't do that then. 0x80 is not safe on a modern PC system (you'll note the Linux kernel changed behaviour here). It may be a debug port but we've seen some hardware do worse things if you touch it. It's also completely out on a limb with EFI based systems which don't necessarily have the legacy stuff present. Alan _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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