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* [Qemu-devel] [PATCH] target/ppc: Allow privileged access to SPR_PCR
@ 2018-05-30 14:42 Joel Stanley
  2018-05-30 15:03 ` no-reply
  2018-05-31  7:38 ` Cédric Le Goater
  0 siblings, 2 replies; 9+ messages in thread
From: Joel Stanley @ 2018-05-30 14:42 UTC (permalink / raw)
  To: David Gibson, Alexander Graf, qemu-ppc, qemu-devel
  Cc: Cédric Le Goater, Benjamin Herrenschmidt, Michael Ellerman,
	Michael Neuling

The powerpc Linux kernel[1] and skiboot firmware[2] recently gained changes
that cause the Processor Compatibility Register (PCR) SPR to be cleared.

These changes cause Linux to fail to boot on the Qemu powernv machine
with an error:

 Trying to write privileged spr 338 (0x152) at 0000000030017f0c

With this patch Qemu makes this register available as a hypervisor
privileged register.

Note that bits set in this register disable features of the processor.
Currently the only register state that is supported is when the register
is zeroed (enable all features). This is sufficient for guests to
once again boot.

[1] https://lkml.kernel.org/r/20180518013742.24095-1-mikey@neuling.org
[2] https://patchwork.ozlabs.org/patch/915932/

Signed-off-by: Joel Stanley <joel@jms.id.au>
---
 target/ppc/helper.h             |  1 +
 target/ppc/misc_helper.c        | 10 ++++++++++
 target/ppc/translate_init.inc.c |  9 +++++++--
 3 files changed, 18 insertions(+), 2 deletions(-)

diff --git a/target/ppc/helper.h b/target/ppc/helper.h
index 19453c68138a..d751f0e21909 100644
--- a/target/ppc/helper.h
+++ b/target/ppc/helper.h
@@ -17,6 +17,7 @@ DEF_HELPER_2(pminsn, void, env, i32)
 DEF_HELPER_1(rfid, void, env)
 DEF_HELPER_1(hrfid, void, env)
 DEF_HELPER_2(store_lpcr, void, env, tl)
+DEF_HELPER_2(store_pcr, void, env, tl)
 #endif
 DEF_HELPER_1(check_tlb_flush_local, void, env)
 DEF_HELPER_1(check_tlb_flush_global, void, env)
diff --git a/target/ppc/misc_helper.c b/target/ppc/misc_helper.c
index 8c8cba5cc6f1..40c39d08ad14 100644
--- a/target/ppc/misc_helper.c
+++ b/target/ppc/misc_helper.c
@@ -20,6 +20,7 @@
 #include "cpu.h"
 #include "exec/exec-all.h"
 #include "exec/helper-proto.h"
+#include "qemu/error-report.h"
 
 #include "helper_regs.h"
 
@@ -186,6 +187,15 @@ void ppc_store_msr(CPUPPCState *env, target_ulong value)
     hreg_store_msr(env, value, 0);
 }
 
+void helper_store_pcr(CPUPPCState *env, target_ulong value)
+{
+    if (value != 0) {
+        error_report("Unimplemented PCR value 0x"TARGET_FMT_lx, value);
+        return;
+    }
+    env->spr[SPR_PCR] = value;
+}
+
 /* This code is lifted from MacOnLinux. It is called whenever
  * THRM1,2 or 3 is read an fixes up the values in such a way
  * that will make MacOS not hang. These registers exist on some
diff --git a/target/ppc/translate_init.inc.c b/target/ppc/translate_init.inc.c
index ab782cb32aaa..bebe6ec5333c 100644
--- a/target/ppc/translate_init.inc.c
+++ b/target/ppc/translate_init.inc.c
@@ -456,6 +456,10 @@ static void spr_write_hid0_601(DisasContext *ctx, int sprn, int gprn)
     /* Must stop the translation as endianness may have changed */
     gen_stop_exception(ctx);
 }
+static void spr_write_pcr(DisasContext *ctx, int sprn, int gprn)
+{
+    gen_helper_store_pcr(cpu_env, cpu_gpr[gprn]);
+}
 #endif
 
 /* Unified bats */
@@ -7957,11 +7961,12 @@ static void gen_spr_power6_common(CPUPPCState *env)
 #endif
     /*
      * Register PCR to report POWERPC_EXCP_PRIV_REG instead of
-     * POWERPC_EXCP_INVAL_SPR.
+     * POWERPC_EXCP_INVAL_SPR in userspace. Permit hypervisor access.
      */
-    spr_register(env, SPR_PCR, "PCR",
+    spr_register_hv(env, SPR_PCR, "PCR",
                  SPR_NOACCESS, SPR_NOACCESS,
                  SPR_NOACCESS, SPR_NOACCESS,
+                 &spr_read_generic, &spr_write_pcr,
                  0x00000000);
 }
 
-- 
2.17.0

^ permalink raw reply related	[flat|nested] 9+ messages in thread
end of thread, other threads:[~2018-06-05  6:49 UTC | newest]

Thread overview: 9+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2018-05-30 14:42 [Qemu-devel] [PATCH] target/ppc: Allow privileged access to SPR_PCR Joel Stanley
2018-05-30 15:03 ` no-reply
2018-05-31  7:38 ` Cédric Le Goater
2018-05-31 11:27   ` [Qemu-devel] [Qemu-ppc] " Greg Kurz
2018-05-31 11:58     ` Joel Stanley
2018-05-31 12:13       ` Greg Kurz
2018-05-31 12:22         ` Joel Stanley
2018-06-04  7:59     ` David Gibson
2018-06-05  6:48       ` Greg Kurz

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