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authorMichael Ellerman <mpe@ellerman.id.au>2021-10-15 23:02:08 +1100
committerMichael Ellerman <mpe@ellerman.id.au>2021-10-16 00:40:03 +1100
commitcdeb5d7d890e14f3b70e8087e745c4a6a7d9f337 (patch)
tree25fabe2a0b33a938d264deeba7c32892660d986d /arch/powerpc
parent9b4416c5095c20e110c82ae602c254099b83b72f (diff)
KVM: PPC: Book3S HV: Make idle_kvm_start_guest() return 0 if it went to guest
We call idle_kvm_start_guest() from power7_offline() if the thread has been requested to enter KVM. We pass it the SRR1 value that was returned from power7_idle_insn() which tells us what sort of wakeup we're processing. Depending on the SRR1 value we pass in, the KVM code might enter the guest, or it might return to us to do some host action if the wakeup requires it. If idle_kvm_start_guest() is able to handle the wakeup, and enter the guest it is supposed to indicate that by returning a zero SRR1 value to us. That was the behaviour prior to commit 10d91611f426 ("powerpc/64s: Reimplement book3s idle code in C"), however in that commit the handling of SRR1 was reworked, and the zeroing behaviour was lost. Returning from idle_kvm_start_guest() without zeroing the SRR1 value can confuse the host offline code, causing the guest to crash and other weirdness. Fixes: 10d91611f426 ("powerpc/64s: Reimplement book3s idle code in C") Cc: stable@vger.kernel.org # v5.2+ Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/20211015133929.832061-2-mpe@ellerman.id.au
Diffstat (limited to 'arch/powerpc')
-rw-r--r--arch/powerpc/kvm/book3s_hv_rmhandlers.S9
1 files changed, 7 insertions, 2 deletions
diff --git a/arch/powerpc/kvm/book3s_hv_rmhandlers.S b/arch/powerpc/kvm/book3s_hv_rmhandlers.S
index ec57952b60b0..eb776d0c5d8e 100644
--- a/arch/powerpc/kvm/book3s_hv_rmhandlers.S
+++ b/arch/powerpc/kvm/book3s_hv_rmhandlers.S
@@ -264,6 +264,7 @@ _GLOBAL(idle_kvm_start_guest)
stdu r1, -SWITCH_FRAME_SIZE(r4)
// Switch to new frame on emergency stack
mr r1, r4
+ std r3, 32(r1) // Save SRR1 wakeup value
SAVE_NVGPRS(r1)
/*
@@ -315,6 +316,10 @@ kvm_unsplit_wakeup:
kvm_secondary_got_guest:
+ // About to go to guest, clear saved SRR1
+ li r0, 0
+ std r0, 32(r1)
+
/* Set HSTATE_DSCR(r13) to something sensible */
ld r6, PACA_DSCR_DEFAULT(r13)
std r6, HSTATE_DSCR(r13)
@@ -394,8 +399,8 @@ kvm_no_guest:
mfspr r4, SPRN_LPCR
rlwimi r4, r3, 0, LPCR_PECE0 | LPCR_PECE1
mtspr SPRN_LPCR, r4
- /* set up r3 for return */
- mfspr r3,SPRN_SRR1
+ // Return SRR1 wakeup value, or 0 if we went into the guest
+ ld r3, 32(r1)
REST_NVGPRS(r1)
ld r1, 0(r1) // Switch back to caller stack
ld r0, 16(r1) // Reload LR