From: Andrew Cooper <andrew.cooper3@citrix.com>
Date: Tue, 6 Aug 2013 13:48:38 +0000 (+0100)
Subject: rombios/ata: Reading this status register has no relevant side effects
X-Git-Tag: archive/raspbian/4.8.0-1+rpi1~1^2~6554
X-Git-Url: https://dgit.raspbian.org/?a=commitdiff_plain;h=db46adf193be09e33fb1778f840cda5de91c777e;p=xen.git

rombios/ata: Reading this status register has no relevant side effects

So taking two traps when one will do is pointless.  This removes 1 of 13
VMExits on the int 0x13 hotpath.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Acked-by: Keir Fraser <keir@xen.org>
---

diff --git a/tools/firmware/rombios/rombios.c b/tools/firmware/rombios/rombios.c
index a3efc618e0..f5557477a5 100644
--- a/tools/firmware/rombios/rombios.c
+++ b/tools/firmware/rombios/rombios.c
@@ -2540,7 +2540,6 @@ static int await_ide(when_done,base,timeout)
   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++;