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KVM: PPC: Book3S HV: Make idle_kvm_start_guest() return 0 if it went to guest

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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 10d91611f4 ("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: 10d91611f4 ("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
This commit is contained in:
Michael Ellerman 2021-10-15 23:02:08 +11:00
parent 9b4416c509
commit cdeb5d7d89
1 changed files with 7 additions and 2 deletions
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9
arch/powerpc/kvm/book3s_hv_rmhandlers.S
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@ -264,6 +264,7 @@ _GLOBAL(idle_kvm_start_guest)
stdu r1, -SWITCH_FRAME_SIZE(r4) stdu r1, -SWITCH_FRAME_SIZE(r4)
// Switch to new frame on emergency stack // Switch to new frame on emergency stack
mr r1, r4 mr r1, r4
std r3, 32(r1) // Save SRR1 wakeup value
SAVE_NVGPRS(r1) SAVE_NVGPRS(r1)
/* /*
@ -315,6 +316,10 @@ kvm_unsplit_wakeup:
kvm_secondary_got_guest: 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 */ /* Set HSTATE_DSCR(r13) to something sensible */
ld r6, PACA_DSCR_DEFAULT(r13) ld r6, PACA_DSCR_DEFAULT(r13)
std r6, HSTATE_DSCR(r13) std r6, HSTATE_DSCR(r13)
@ -394,8 +399,8 @@ kvm_no_guest:
mfspr r4, SPRN_LPCR mfspr r4, SPRN_LPCR
rlwimi r4, r3, 0, LPCR_PECE0 | LPCR_PECE1 rlwimi r4, r3, 0, LPCR_PECE0 | LPCR_PECE1
mtspr SPRN_LPCR, r4 mtspr SPRN_LPCR, r4
/* set up r3 for return */ // Return SRR1 wakeup value, or 0 if we went into the guest
mfspr r3,SPRN_SRR1 ld r3, 32(r1)
REST_NVGPRS(r1) REST_NVGPRS(r1)
ld r1, 0(r1) // Switch back to caller stack ld r1, 0(r1) // Switch back to caller stack
ld r0, 16(r1) // Reload LR ld r0, 16(r1) // Reload LR