Thread (11 messages) 11 messages, 3 authors, 2024-02-13

Re: [PATCH] powerpc: Add gpr1 and fpu save/restore functions

From: Timothy Pearson <tpearson@raptorengineering.com>
Date: 2024-02-12 18:32:06


----- Original Message -----
From: "Segher Boessenkool" <redacted>
To: "Timothy Pearson" <tpearson@raptorengineering.com>
Cc: "linuxppc-dev" <redacted>
Sent: Monday, February 12, 2024 12:23:22 PM
Subject: Re: [PATCH] powerpc: Add gpr1 and fpu save/restore functions
quoted hunk ↗ jump to hunk
On Mon, Feb 12, 2024 at 12:07:03PM -0600, Timothy Pearson wrote:
quoted
quoted
I have done it for *all* architectures some ten years ago.  Never found
any problem.
That makes sense, what I mean by invasive is that we'd need buy-in from the
other
maintainers across all of the affected architectures.  Is that likely to occur?
I don't know.  Here is my PowerPC-specific patch, it's a bit older, it
might not apply cleanly anymore, the changes needed should be obvious
though:


=== 8< ===
commit f16dfa5257eb14549ce22243fb2b465615085134
Author: Segher Boessenkool [off-list ref]
Date:   Sat May 3 03:48:06 2008 +0200

   powerpc: Link vmlinux against libgcc.a
diff --git a/arch/powerpc/Makefile b/arch/powerpc/Makefile
index b7212b619c52..0a2fac6ffc1c 100644
--- a/arch/powerpc/Makefile
+++ b/arch/powerpc/Makefile
@@ -158,6 +158,9 @@ core-y                              += arch/powerpc/kernel/
core-$(CONFIG_XMON)            += arch/powerpc/xmon/
core-$(CONFIG_KVM)             += arch/powerpc/kvm/

+LIBGCC := $(shell $(CC) $(KBUILD_CFLAGS) -print-libgcc-file-name)
+libs-y += $(LIBGCC)
+
drivers-$(CONFIG_OPROFILE)     += arch/powerpc/oprofile/

# Default to zImage, override when needed
=== 8< ===
OK.  PowerPC maintainers, how would you prefer to handle this?
quoted
quoted
There are better options than -Os, fwiw.  Some --param's give smaller
*and* faster kernels.  What exactly is best is heavily arch-dependent
though (as well as dependent on the application code, the kernel code in
this case) :-(
I've been through this a few times, and -Os is the only option that makes
things (just barely) fit unfortunately.
-O2 with appropriate inlining tuning beats -Os every day of the week,
in my experience.
On 6.6 it's 24MiB vs 40MiB, O2 vs. Os. :(
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