Revision 8764ed55c9705e426d889ff16c26f398bba70b9b authored by Sean Christopherson on 29 April 2019, 14:04:15 UTC, committed by Paolo Bonzini on 30 April 2019, 19:03:42 UTC
KVM's recent bug fix to update %rip after emulating I/O broke userspace that relied on the previous behavior of incrementing %rip prior to exiting to userspace. When running a Windows XP guest on AMD hardware, Qemu may patch "OUT 0x7E" instructions in reaction to the OUT itself. Because KVM's old behavior was to increment %rip before exiting to userspace to handle the I/O, Qemu manually adjusted %rip to account for the OUT instruction. Arguably this is a userspace bug as KVM requires userspace to re-enter the kernel to complete instruction emulation before taking any other actions. That being said, this is a bit of a grey area and breaking userspace that has worked for many years is bad. Pre-increment %rip on OUT to port 0x7e before exiting to userspace to hack around the issue. Fixes: 45def77ebf79e ("KVM: x86: update %rip after emulating IO") Reported-by: Simon Becherer <simon@becherer.de> Reported-and-tested-by: Iakov Karpov <srid@rkmail.ru> Reported-by: Gabriele Balducci <balducci@units.it> Reported-by: Antti Antinoja <reader@fennosys.fi> Cc: stable@vger.kernel.org Cc: Takashi Iwai <tiwai@suse.com> Cc: Jiri Slaby <jslaby@suse.com> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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File | Mode | Size |
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Makefile | -rw-r--r-- | 361 bytes |
compat.c | -rw-r--r-- | 2.2 KB |
ipc_sysctl.c | -rw-r--r-- | 5.9 KB |
mq_sysctl.c | -rw-r--r-- | 2.9 KB |
mqueue.c | -rw-r--r-- | 40.1 KB |
msg.c | -rw-r--r-- | 30.5 KB |
msgutil.c | -rw-r--r-- | 3.6 KB |
namespace.c | -rw-r--r-- | 4.6 KB |
sem.c | -rw-r--r-- | 62.1 KB |
shm.c | -rw-r--r-- | 43.0 KB |
syscall.c | -rw-r--r-- | 5.1 KB |
util.c | -rw-r--r-- | 22.1 KB |
util.h | -rw-r--r-- | 8.9 KB |
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