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authorSuraj Jitindar Singh <sjitindarsingh@gmail.com>2019-03-01 13:43:15 +1100
committerDavid Gibson <david@gibson.dropbear.id.au>2019-03-12 12:07:49 +1100
commita8dafa525181e57405b7ef4bf7c212bf5f6d8ca1 (patch)
tree53fcc83a2b381812d4838a57a9fda15322f80bb4 /hw/ppc/spapr.c
parentc982f5cf9ab9e60a8255f9cc72362c932c252471 (diff)
target/ppc: Implement large decrementer support for TCG
Prior to POWER9 the decrementer was a 32-bit register which decremented with each tick of the timebase. From POWER9 onwards the decrementer can be set to operate in a mode called large decrementer where it acts as a n-bit decrementing register which is visible as a 64-bit register, that is the value of the decrementer is sign extended to 64 bits (where n is implementation dependant). The mode in which the decrementer operates is controlled by the LPCR_LD bit in the logical paritition control register (LPCR). >From POWER9 onwards the HDEC (hypervisor decrementer) was enlarged to h-bits, also sign extended to 64 bits (where h is implementation dependant). Note this isn't configurable and is always enabled. On POWER9 the large decrementer and hdec are both 56 bits, as represented by the lrg_decr_bits cpu class property. Since they are the same size we only add one property for now, which could be extended in the case they ever differ in the future. We also add the lrg_decr_bits property for POWER5+/7/8 since it is used to determine the size of the hdec, which is only generated on the POWER5+ processor and later. On these processors it is 32 bits. Signed-off-by: Suraj Jitindar Singh <sjitindarsingh@gmail.com> Signed-off-by: Cédric Le Goater <clg@kaod.org> Message-Id: <20190301024317.22137-2-sjitindarsingh@gmail.com> [dwg: Small style fixes] Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Diffstat (limited to 'hw/ppc/spapr.c')
-rw-r--r--hw/ppc/spapr.c8
1 files changed, 8 insertions, 0 deletions
diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
index e07e5370d3..6b54ad260a 100644
--- a/hw/ppc/spapr.c
+++ b/hw/ppc/spapr.c
@@ -558,6 +558,14 @@ static void spapr_populate_cpu_dt(CPUState *cs, void *fdt, int offset,
pcc->radix_page_info->count *
sizeof(radix_AP_encodings[0]))));
}
+
+ /*
+ * We set this property to let the guest know that it can use the large
+ * decrementer and its width in bits.
+ */
+ if (spapr_get_cap(spapr, SPAPR_CAP_LARGE_DECREMENTER) != SPAPR_CAP_OFF)
+ _FDT((fdt_setprop_u32(fdt, offset, "ibm,dec-bits",
+ pcc->lrg_decr_bits)));
}
static void spapr_populate_cpus_dt_node(void *fdt, sPAPRMachineState *spapr)