[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH 3 of 5] rombios/ata: Reading this status register has no relevant side effects
On 26/11/12 16:51, Ian Campbell wrote: > No relevant side effects according to some spec or according to the > current qemu implementation? > > Does it have any "irrelevant" side effects? I am not sure whether the spec gurarentees no side effects, but this is according to the qemu implementation. The codepath has no side effects we could determine. ~Andrew > > On Mon, 2012-11-26 at 16:41 +0000, Andrew Cooper wrote: >> So taking two traps when one will do is pointless. This codepath is on the >> int >> 0x13 hot path, and removing it has about a 30% reduction in the number of >> traps >> to Qemu during Win7 boot. >> >> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx> >> >> diff -r c223c044afbf -r a8645d836a0e tools/firmware/rombios/rombios.c >> --- a/tools/firmware/rombios/rombios.c >> +++ b/tools/firmware/rombios/rombios.c >> @@ -2540,7 +2540,6 @@ static int await_ide(when_done,base,time >> Bit32u time=0,last=0; >> Bit16u status; >> Bit8u result; >> - status = inb(base + ATA_CB_STAT); // for the times you're supposed to >> throw one away >> for(;;) { >> status = inb(base+ATA_CB_STAT); >> time++; >> >> _______________________________________________ >> Xen-devel mailing list >> Xen-devel@xxxxxxxxxxxxx >> http://lists.xen.org/xen-devel > -- Andrew Cooper - Dom0 Kernel Engineer, Citrix XenServer T: +44 (0)1223 225 900, http://www.citrix.com _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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