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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Alexey Kardashevskiy <aik@ozlabs.ru>,
        Nicholas Piggin <npiggin@gmail.com>,
        Michael Ellerman <mpe@ellerman.id.au>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 5.4 044/108] KVM: PPC: Book3S: Fix CONFIG_TRANSACTIONAL_MEM=n crash
Date:   Mon, 26 Jul 2021 17:38:45 +0200
Message-Id: <20210726153833.101099140@linuxfoundation.org>
In-Reply-To: <20210726153831.696295003@linuxfoundation.org>
References: <20210726153831.696295003@linuxfoundation.org>
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From: Nicholas Piggin <npiggin@gmail.com>

[ Upstream commit bd31ecf44b8e18ccb1e5f6b50f85de6922a60de3 ]

When running CPU_FTR_P9_TM_HV_ASSIST, HFSCR[TM] is set for the guest
even if the host has CONFIG_TRANSACTIONAL_MEM=n, which causes it to be
unprepared to handle guest exits while transactional.

Normal guests don't have a problem because the HTM capability will not
be advertised, but a rogue or buggy one could crash the host.

Fixes: 4bb3c7a0208f ("KVM: PPC: Book3S HV: Work around transactional memory bugs in POWER9")
Reported-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210716024310.164448-1-npiggin@gmail.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 arch/powerpc/kvm/book3s_hv.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c
index 9011857c0434..bba358f13471 100644
--- a/arch/powerpc/kvm/book3s_hv.c
+++ b/arch/powerpc/kvm/book3s_hv.c
@@ -2306,8 +2306,10 @@ static struct kvm_vcpu *kvmppc_core_vcpu_create_hv(struct kvm *kvm,
 		HFSCR_DSCR | HFSCR_VECVSX | HFSCR_FP;
 	if (cpu_has_feature(CPU_FTR_HVMODE)) {
 		vcpu->arch.hfscr &= mfspr(SPRN_HFSCR);
+#ifdef CONFIG_PPC_TRANSACTIONAL_MEM
 		if (cpu_has_feature(CPU_FTR_P9_TM_HV_ASSIST))
 			vcpu->arch.hfscr |= HFSCR_TM;
+#endif
 	}
 	if (cpu_has_feature(CPU_FTR_TM_COMP))
 		vcpu->arch.hfscr |= HFSCR_TM;
-- 
2.30.2