[PATCH 1/2] kvm/xive: Workaround P9 DD1.0 bug with IPB bit loss
From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Date: 2017-08-18 02:10:59
Also in:
kvm
Subsystem:
kernel virtual machine for powerpc (kvm/powerpc), linux for powerpc (32-bit and 64-bit), the rest · Maintainers:
Madhavan Srinivasan, Linus Torvalds
Thankfully it only happens when manually manipulating CPPR which is rather quite rare. Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org> --- arch/powerpc/kvm/book3s_xive_template.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-)
diff --git a/arch/powerpc/kvm/book3s_xive_template.c b/arch/powerpc/kvm/book3s_xive_template.c
index 4636ca6e7d38..150be86b1018 100644
--- a/arch/powerpc/kvm/book3s_xive_template.c
+++ b/arch/powerpc/kvm/book3s_xive_template.c@@ -16,7 +16,16 @@ static void GLUE(X_PFX,ack_pending)(struct kvmppc_xive_vcpu *xc) u8 cppr; u16 ack; - /* XXX DD1 bug workaround: Check PIPR vs. CPPR first ! */ + /* + * DD1 bug workaround: If PIPR is less favored than CPPR + * ignore the interrupt or we might incorrectly lose an IPB + * bit. + */ + if (cpu_has_feature(CPU_FTR_POWER9_DD1)) { + u8 pipr = __x_readb(__x_tima + TM_QW1_OS + TM_PIPR); + if (pipr >= xc->hw_cppr) + return; + } /* Perform the acknowledge OS to register cycle. */ ack = be16_to_cpu(__x_readw(__x_tima + TM_SPC_ACK_OS_REG));