powerpc: Save/restore PPR for KVM hypercalls
authorSuresh E. Warrier <warrier@linux.vnet.ibm.com>
Mon, 3 Nov 2014 04:46:42 +0000 (15:46 +1100)
committerMichael Ellerman <mpe@ellerman.id.au>
Wed, 12 Nov 2014 04:53:25 +0000 (15:53 +1100)
commit8b91a2554610ac5e341de8fb0b5715fe90a0f2e2
tree674e4e96d56efa88a6d2562e2e4f93d3a55ebd7c
parentd1d5304fcbc519f5fb12cbcca9c4fdd1d94447d7
powerpc: Save/restore PPR for KVM hypercalls

The system call FLIH (first-level interrupt handler) at 0xc00
unconditionally sets hardware priority to medium. For hypercalls, this
means we lose guest OS priority. The front end (do_kvm_0x**) to the
KVM interrupt handler always assumes that PPR priority is saved in
PACA exception save area, so it copies this to the kvm_hstate
structure. For hypercalls, this would be the saved priority from any
previous exception. Eventually, the guest gets resumed with an
incorrect priority.

The fix is to save the PPR priority in PACA exception save area before
switching HMT priorities in the FLIH so that existing code described above
in the KVM interrupt handler can copy it from there into the VCPU's saved
context.

Signed-off-by: Suresh Warrier <warrier@linux.vnet.ibm.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>
[mpe: Dropped HMT_MEDIUM_PPR_DISCARD and reworded comment]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
arch/powerpc/kernel/exceptions-64s.S