linux-kernel - [PATCH AUTOSEL 4.19 095/209] KVM: PPC: Book3S PR: Exiting split hack mode needs to fixup both PC and LR

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Date:   Tue, 12 Nov 2019 20:48:31 -0500
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Cameron Kaiser <spectre@...odgap.com>,
        Paul Mackerras <paulus@...abs.org>,
        Sasha Levin <sashal@...nel.org>, kvm-ppc@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org
Subject: [PATCH AUTOSEL 4.19 095/209] KVM: PPC: Book3S PR: Exiting split hack mode needs to fixup both PC and LR

From: Cameron Kaiser <spectre@...odgap.com>

[ Upstream commit 1006284c5e411872333967b1970c2ca46a9e225f ]

When an OS (currently only classic Mac OS) is running in KVM-PR and makes a
linked jump from code with split hack addressing enabled into code that does
not, LR is not correctly updated and reflects the previously munged PC.

To fix this, this patch undoes the address munge when exiting split
hack mode so that code relying on LR being a proper address will now
execute. This does not affect OS X or other operating systems running
on KVM-PR.

Signed-off-by: Cameron Kaiser <spectre@...odgap.com>
Signed-off-by: Paul Mackerras <paulus@...abs.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 arch/powerpc/kvm/book3s.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/powerpc/kvm/book3s.c b/arch/powerpc/kvm/book3s.c
index 281f074581a3b..cc05f346e0421 100644
--- a/arch/powerpc/kvm/book3s.c
+++ b/arch/powerpc/kvm/book3s.c
@@ -78,8 +78,11 @@ void kvmppc_unfixup_split_real(struct kvm_vcpu *vcpu)
 {
 	if (vcpu->arch.hflags & BOOK3S_HFLAG_SPLIT_HACK) {
 		ulong pc = kvmppc_get_pc(vcpu);
+		ulong lr = kvmppc_get_lr(vcpu);
 		if ((pc & SPLIT_HACK_MASK) == SPLIT_HACK_OFFS)
 			kvmppc_set_pc(vcpu, pc & ~SPLIT_HACK_MASK);
+		if ((lr & SPLIT_HACK_MASK) == SPLIT_HACK_OFFS)
+			kvmppc_set_lr(vcpu, lr & ~SPLIT_HACK_MASK);
 		vcpu->arch.hflags &= ~BOOK3S_HFLAG_SPLIT_HACK;
 	}
 }
-- 
2.20.1