powerpc/64s: Revert setting of LPCR[LPES] on POWER9

The XIVE enablement patches included a change to set the LPES (Logical
Partitioning Environment Selector) bit (bit # 3) in LPCR (Logical Partitioning
Control Register) on POWER9 hosts. This bit sets external interrupts to guest
delivery mode, which uses SRR0/1. The host's EE interrupt handler is written to
expect HSRR0/1 (for earlier CPUs). This should be fine because XIVE is
configured not to deliver EEs to the host (Hypervisor Virtulization Interrupt is
used instead) so the EE handler should never be executed.

However a bug in interrupt controller code, hardware, or odd configuration of a
simulator could result in the host getting an EE incorrectly. Keeping the EE
delivery mode matching the host EE handler prevents strange crashes due to using
the wrong exception registers.

KVM will configure the LPCR to set LPES prior to running a guest so that EEs are
delivered to the guest using SRR0/1.

Fixes: 08a1e650cc ("powerpc: Fixup LPCR:PECE and HEIC setting on POWER9")
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
[mpe: Massage change log to avoid referring to LPES0 which is now renamed LPES]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

diff --git a/arch/powerpc/kernel/cpu_setup_power.S b/arch/powerpc/kernel/cpu_setup_power.S
index 7013ae3d16755a6fce870f49deea70fea6869fc8..1fce4ddd2e6c6f254d917545380b21f05253281f 100644 (file)
--- a/arch/powerpc/kernel/cpu_setup_power.S
+++ b/arch/powerpc/kernel/cpu_setup_power.S
@@ -107,7 +107,7 @@ _GLOBAL(__setup_cpu_power9)
        or      r3, r3, r4
        LOAD_REG_IMMEDIATE(r4, LPCR_UPRT | LPCR_HR)
        andc    r3, r3, r4
-       li      r4,(LPCR_LPES0 >> LPCR_LPES_SH)
+       li      r4,0 /* LPES = 0 */
        bl      __init_LPCR
        bl      __init_HFSCR
        bl      __init_tlb_power9
@@ -131,7 +131,7 @@ _GLOBAL(__restore_cpu_power9)
        or      r3, r3, r4
        LOAD_REG_IMMEDIATE(r4, LPCR_UPRT | LPCR_HR)
        andc    r3, r3, r4
-       li      r4,(LPCR_LPES0 >> LPCR_LPES_SH)
+       li      r4,0 /* LPES = 0 */
        bl      __init_LPCR
        bl      __init_HFSCR
        bl      __init_tlb_power9