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Re: [Qemu-devel] [PATCH v3 06/24] target-ppc: Enable writes to user-priv

From: Alexander Graf
Subject: Re: [Qemu-devel] [PATCH v3 06/24] target-ppc: Enable writes to user-privileged PMU registers
Date: Wed, 28 May 2014 12:47:34 +0200
User-agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.9; rv:24.0) Gecko/20100101 Thunderbird/24.5.0

On 28.05.14 04:28, Alexey Kardashevskiy wrote:
On 05/28/2014 10:03 AM, Alexander Graf wrote:
On 27.05.14 12:37, Alexey Kardashevskiy wrote:
This adds spr_write_ureg() helper and uses it for UPMCx and MMCR0 SPRs.

Signed-off-by: Alexey Kardashevskiy <address@hidden>
   target-ppc/translate_init.c | 25 +++++++++++++++----------
   1 file changed, 15 insertions(+), 10 deletions(-)

diff --git a/target-ppc/translate_init.c b/target-ppc/translate_init.c
index 88acf70..595fd3f 100644
--- a/target-ppc/translate_init.c
+++ b/target-ppc/translate_init.c
@@ -175,6 +175,11 @@ static void spr_read_ureg (void *opaque, int gprn,
int sprn)
       gen_load_spr(cpu_gpr[gprn], sprn + 0x10);
   +static void spr_write_ureg(void *opaque, int gprn, int sprn)
+    gen_store_spr(sprn + 0x10, cpu_gpr[gprn]);
   /* SPR common to all non-embedded PowerPC */
   /* DECR */
   #if !defined(CONFIG_USER_ONLY)
@@ -7379,28 +7384,28 @@ static void gen_spr_book3s_pmu(CPUPPCState *env)
                    &spr_read_generic, SPR_NOACCESS,
       spr_register(env, SPR_POWER_UMMCR0, "UMMCR0",
-                 &spr_read_ureg, SPR_NOACCESS,
-                 &spr_read_ureg, SPR_NOACCESS,
+                 &spr_read_ureg, &spr_write_ureg,
+                 &spr_read_ureg, &spr_write_ureg,
Are you sure about this? The 970MP spec says "Performance Monitor Registers
(For Reading)". In general, I don't think we would ever really have an
spr_write_ureg user.
Uffff. It is worse than that. They were read-only for user space till 2.07,
now they might be write-enabled too because of EBB. Do I really have to
implement exceptions on accessing them as described in "6.2.11 Hypervisor
Facility Status and Control Register" (2.07)? It is getting too much just
to get H_SET_MODE(AIL) accepted, no? :-)

Just treat them as not write enabled and leave the EBB magic for later. Indicate that it's missing and what needs to be done with a comment :).


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