From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:52364) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZtWrb-0006Z3-1f for qemu-devel@nongnu.org; Tue, 03 Nov 2015 03:22:43 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ZtWrW-00063s-JW for qemu-devel@nongnu.org; Tue, 03 Nov 2015 03:22:43 -0500 References: <1445608598-24485-1-git-send-email-mark.cave-ayland@ilande.co.uk> <1445608598-24485-2-git-send-email-mark.cave-ayland@ilande.co.uk> From: Thomas Huth Message-ID: <56386EC8.4050608@redhat.com> Date: Tue, 3 Nov 2015 09:22:32 +0100 MIME-Version: 1.0 In-Reply-To: <1445608598-24485-2-git-send-email-mark.cave-ayland@ilande.co.uk> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH 01/13] PPC: Allow Rc bit to be set on mtspr List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Mark Cave-Ayland , qemu-devel@nongnu.org, qemu-ppc@nongnu.org, agraf@suse.de, david@gibson.dropbear.id.au, cormac@c-obrien.org On 23/10/15 15:56, Mark Cave-Ayland wrote: > From: Alexander Graf > > According to the ISA setting the Rc bit on mtspr is undefined behavior. > Real 750 hardware simply ignores the bit and doesn't touch cr0 though. According to PowerISA 2.07, chapter 1.1.3: "Reserved fields in instructions are ignored by the pro- cessor." And the lowest bit of the mtspr opcode is marked as reserved. So I think this is not just a hack, but even a proper fix. > Unfortunately, Mac OS 9 relies on this fact and executes a few mtspr > instructions (to set XER for example) with Rc set. > > So let's handle the bit the same way hardware does and ignore it. > > Signed-off-by: Alexander Graf > Signed-off-by: Mark Cave-Ayland > --- > target-ppc/translate.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/target-ppc/translate.c b/target-ppc/translate.c > index c2bc1a7..d1f0f13 100644 > --- a/target-ppc/translate.c > +++ b/target-ppc/translate.c > @@ -9884,7 +9884,7 @@ GEN_HANDLER(mtcrf, 0x1F, 0x10, 0x04, 0x00000801, PPC_MISC), > GEN_HANDLER(mtmsrd, 0x1F, 0x12, 0x05, 0x001EF801, PPC_64B), > #endif > GEN_HANDLER(mtmsr, 0x1F, 0x12, 0x04, 0x001FF801, PPC_MISC), > -GEN_HANDLER(mtspr, 0x1F, 0x13, 0x0E, 0x00000001, PPC_MISC), > +GEN_HANDLER(mtspr, 0x1F, 0x13, 0x0E, 0x00000000, PPC_MISC), > GEN_HANDLER(dcbf, 0x1F, 0x16, 0x02, 0x03C00001, PPC_CACHE), > GEN_HANDLER(dcbi, 0x1F, 0x16, 0x0E, 0x03E00001, PPC_CACHE), > GEN_HANDLER(dcbst, 0x1F, 0x16, 0x01, 0x03E00001, PPC_CACHE), Reviewed-by: Thomas Huth