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KVM: PPC: Book3S HV: Sanitize special-purpose register values on guest exit

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commit ccec44563b18a0ce90e2d4f332784b3cb25c8e9c upstream.

Thomas Huth discovered that a guest could cause a hard hang of a
host CPU by setting the Instruction Authority Mask Register (IAMR)
to a suitable value.  It turns out that this is because when the
code was added to context-switch the new special-purpose registers
(SPRs) that were added in POWER8, we forgot to add code to ensure
that they were restored to a sane value on guest exit.

This adds code to set those registers where a bad value could
compromise the execution of the host kernel to a suitable neutral
value on guest exit.

Fixes: b005255e12a3
Reported-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Paul Mackerras 2016-03-05 19:34:39 +11:00 committed by Greg Kroah-Hartman
parent 7893953054
commit 1c463a390a
1 changed files with 14 additions and 0 deletions
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14
arch/powerpc/kvm/book3s_hv_rmhandlers.S
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@ -1370,6 +1370,20 @@ END_FTR_SECTION_IFCLR(CPU_FTR_ARCH_207S)
std r6, VCPU_ACOP(r9)
stw r7, VCPU_GUEST_PID(r9)
std r8, VCPU_WORT(r9)
/*
* Restore various registers to 0, where non-zero values
* set by the guest could disrupt the host.
*/
li r0, 0
mtspr SPRN_IAMR, r0
mtspr SPRN_CIABR, r0
mtspr SPRN_DAWRX, r0
mtspr SPRN_TCSCR, r0
mtspr SPRN_WORT, r0
/* Set MMCRS to 1<<31 to freeze and disable the SPMC counters */
li r0, 1
sldi r0, r0, 31
mtspr SPRN_MMCRS, r0
8:
/* Save and reset AMR and UAMOR before turning on the MMU */