From: "Nicholas Piggin" <npiggin@gmail.com>
To: "BALATON Zoltan" <balaton@eik.bme.hu>
Cc: <qemu-devel@nongnu.org>, <qemu-ppc@nongnu.org>, <clg@kaod.org>,
"Greg Kurz" <groug@kaod.org>,
"Daniel Henrique Barboza" <danielhb413@gmail.com>
Subject: Re: [PATCH v3 09/14] target/ppc: Move patching nip from exception handler to helper_scv
Date: Wed, 28 Jun 2023 11:03:55 +1000 [thread overview]
Message-ID: <CTNVNQVXBXXU.L2P609T3RN13@wheely> (raw)
In-Reply-To: <434967dc-b631-f1d2-0267-93695c1e806b@eik.bme.hu>
On Wed Jun 28, 2023 at 3:40 AM AEST, BALATON Zoltan wrote:
> On Mon, 26 Jun 2023, Nicholas Piggin wrote:
> > On Tue Jun 20, 2023 at 8:47 PM AEST, BALATON Zoltan wrote:
> >> On Tue, 20 Jun 2023, Nicholas Piggin wrote:
> >>> On Fri Jun 16, 2023 at 9:03 AM AEST, BALATON Zoltan wrote:
> >>>> From: Nicholas Piggin <npiggin@gmail.com>
> >>>>
> >>>> Unlike sc, for scv a facility unavailable interrupt must be generated
> >>>> if FSCR[SCV]=0 so we can't raise the exception with nip set to next
> >>>> instruction but we can move advancing nip if the FSCR check passes to
> >>>> helper_scv so the exception handler does not need to change it.
> >>>>
> >>>> [balaton: added commit message]
> >>>> Signed-off-by: BALATON Zoltan <balaton@eik.bme.hu>
> >>>
> >>> Ah you sent it, fine, thank you. But actually now I look again,
> >>> now we're off by one in the other direction for the dumps.
> >>
> >> This is mentioned in the commit message for the patch changing sc. I think
> >> we should not patch nip in the dump so we actually dump what the CPU
> >> should have and match the ISA docs.
> >>
> >>> So... probably your way is still better because it matches the
> >>> interrupt semantics of the ISA when executing the instruction,
> >>> but it needs this patch:
> >>
> >> OK so then I'm confused why we need nip - 4 in dumps?
> >
> > Sorry I missed your reply here. We want nip - 4 in dumps so the
> > address of the syscall is the sc instruction itself, not the
> > random one after it.
>
> Although that's how it was in QEMU before
Current upstream QEMU dumps syscall address of sc instruction. After
patch 8 and 9, it will dump the address of the instruction after it.
> that's not how it is on real
> hardware so I don't think we should keep this and just log what a real CPU
> would have and people should know how to interpret that after consulting
> the ISA docs.
I did get the feeling it was nicer your way, OTOH there really is not
anything in the ISA that requires a particular implementation. QEMU is
a real implementation of the ISA anyway. You could argue it's more
consistent for QEMU to keep env->nip as the address of instruction that
caused the interrupt, and then the sc fixup is restricted to setting
SRR0. I'm on the fence about it now.
Thanks,
Nick
next prev parent reply other threads:[~2023-06-28 1:05 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-06-15 23:03 [PATCH v3 00/14] Misc clean ups to target/ppc exception handling BALATON Zoltan
2023-06-15 23:03 ` [PATCH v3 01/14] target/ppc: Remove some superfluous parentheses BALATON Zoltan
2023-06-15 23:03 ` [PATCH v3 02/14] target/ppc: Remove unneeded parameter from powerpc_reset_wakeup() BALATON Zoltan
2023-06-15 23:03 ` [PATCH v3 03/14] target/ppc: Move common check in exception handlers to a function BALATON Zoltan
2023-06-15 23:03 ` [PATCH v3 04/14] target/ppc: Use env_cpu for cpu_abort in excp_helper BALATON Zoltan
2023-06-20 4:54 ` Nicholas Piggin
2023-06-20 10:50 ` BALATON Zoltan
2023-06-15 23:03 ` [PATCH v3 05/14] target/ppc: Remove some more local CPUState variables only used once BALATON Zoltan
2023-06-20 5:01 ` Nicholas Piggin
2023-06-15 23:03 ` [PATCH v3 06/14] target/ppc: Readability improvements in exception handlers BALATON Zoltan
2023-06-15 23:03 ` [PATCH v3 07/14] target/ppd: Remove unused define BALATON Zoltan
2023-06-18 12:48 ` Bernhard Beschow
2023-06-15 23:03 ` [PATCH v3 08/14] target/ppc: Fix gen_sc to use correct nip BALATON Zoltan
2023-06-20 4:03 ` Nicholas Piggin
2023-06-15 23:03 ` [PATCH v3 09/14] target/ppc: Move patching nip from exception handler to helper_scv BALATON Zoltan
2023-06-20 4:09 ` Nicholas Piggin
2023-06-20 10:47 ` BALATON Zoltan
2023-06-26 11:25 ` Nicholas Piggin
2023-06-27 17:40 ` BALATON Zoltan
2023-06-28 1:03 ` Nicholas Piggin [this message]
2023-06-26 11:28 ` Nicholas Piggin
2023-06-15 23:03 ` [PATCH v3 10/14] target/ppc: Simplify syscall exception handlers BALATON Zoltan
2023-06-20 5:05 ` Nicholas Piggin
2023-06-15 23:03 ` [PATCH v3 11/14] target/ppc: Get CPUState in one step BALATON Zoltan
2023-06-15 23:03 ` [PATCH v3 12/14] target/ppc: Clean up ifdefs in excp_helper.c, part 1 BALATON Zoltan
2023-06-20 5:07 ` Nicholas Piggin
2023-06-20 10:52 ` BALATON Zoltan
2023-06-15 23:03 ` [PATCH v3 13/14] target/ppc: Clean up ifdefs in excp_helper.c, part 2 BALATON Zoltan
2023-06-15 23:03 ` [PATCH v3 14/14] target/ppc: Clean up ifdefs in excp_helper.c, part 3 BALATON Zoltan
2023-06-30 19:52 ` [PATCH v3 00/14] Misc clean ups to target/ppc exception handling Daniel Henrique Barboza
2023-06-30 22:57 ` BALATON Zoltan
2023-07-01 6:39 ` Daniel Henrique Barboza
2023-07-01 9:39 ` BALATON Zoltan
2023-07-01 9:59 ` Daniel Henrique Barboza
2023-07-02 12:36 ` BALATON Zoltan
2023-07-03 10:09 ` Daniel Henrique Barboza
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=CTNVNQVXBXXU.L2P609T3RN13@wheely \
--to=npiggin@gmail.com \
--cc=balaton@eik.bme.hu \
--cc=clg@kaod.org \
--cc=danielhb413@gmail.com \
--cc=groug@kaod.org \
--cc=qemu-devel@nongnu.org \
--cc=qemu-ppc@nongnu.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).