Power11 has the same PCR (Processor Compatibility Register) value, as
Power10.
Due to this, QEMU considers Power11 as a valid compat-mode for Power10,
ie. earlier it was possible to run QEMU with '-M
pseries,max-compat-mode=power11 --cpu power10'
Same PCR also introduced a regression where `-M pseries --cpu power10`
boots as Power11 (ie. logical PVR is of Power11, even though PVR is Power10).
The regression was due to 'do_client_architecture_support' checking for
valid compat modes and finding Power11 to be a valid compat mode for
Power10 (it happens even without passing 'max-compat-mode' explicitly).
Fix compat-mode issue and regression, by ensuring a future Power
processor (with a higher logical_pvr value, eg. P11) cannot be valid
compat-mode for an older Power processor (eg. P10)
Cc: Cédric Le Goater <c...@kaod.org>
Cc: Daniel Henrique Barboza <danielhb...@gmail.com>
Cc: Harsh Prateek Bora <hars...@linux.ibm.com>
Cc: Mahesh J Salgaonkar <mah...@linux.ibm.com>
Cc: Madhavan Srinivasan <ma...@linux.ibm.com>
Cc: Nicholas Piggin <npig...@gmail.com>
Reviewed-by: Nicholas Piggin <npig...@gmail.com>
Signed-off-by: Aditya Gupta <adit...@linux.ibm.com>
---
target/ppc/compat.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/target/ppc/compat.c b/target/ppc/compat.c
index ebef2cccecf3..5b20fd7ef04c 100644
--- a/target/ppc/compat.c
+++ b/target/ppc/compat.c
@@ -132,6 +132,10 @@ static bool pcc_compat(PowerPCCPUClass *pcc, uint32_t
compat_pvr,
/* Outside specified range */
return false;
}
+ if (compat->pvr > pcc->spapr_logical_pvr) {
+ /* Older CPU cannot support a newer processor's compat mode */
+ return false;
+ }
if (!(pcc->pcr_supported & compat->pcr_level)) {
/* Not supported by this CPU */
return false;
--
2.45.2
