This is a note to let you know that I've just added the patch titled
powerpc: Fix context switch DSCR on POWER8
to the 3.10-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
powerpc-fix-context-switch-dscr-on-power8.patch
and it can be found in the queue-3.10 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 2517617e0de65f8f7cfe75cae745d06b1fa98586 Mon Sep 17 00:00:00 2001
From: Michael Neuling <mikey@xxxxxxxxxxx>
Date: Fri, 9 Aug 2013 17:29:29 +1000
Subject: powerpc: Fix context switch DSCR on POWER8
From: Michael Neuling <mikey@xxxxxxxxxxx>
commit 2517617e0de65f8f7cfe75cae745d06b1fa98586 upstream.
POWER8 allows the DSCR to be accessed directly from userspace via a new SPR
number 0x3 (Rather than 0x11. DSCR SPR number 0x11 is still used on POWER8 but
like POWER7, is only accessible in HV and OS modes). Currently, we allow this
by setting H/FSCR DSCR bit on boot.
Unfortunately this doesn't work, as the kernel needs to see the DSCR change so
that it knows to no longer restore the system wide version of DSCR on context
switch (ie. to set thread.dscr_inherit).
This clears the H/FSCR DSCR bit initially. If a process then accesses the DSCR
(via SPR 0x3), it'll trap into the kernel where we set thread.dscr_inherit in
facility_unavailable_exception().
We also change _switch() so that we set or clear the H/FSCR DSCR bit based on
the thread.dscr_inherit.
Signed-off-by: Michael Neuling <mikey@xxxxxxxxxxx>
Signed-off-by: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/powerpc/kernel/entry_64.S | 27 ++++++++++++++++++-
arch/powerpc/kernel/traps.c | 58 ++++++++++++++++++++++++-----------------
2 files changed, 60 insertions(+), 25 deletions(-)
--- a/arch/powerpc/kernel/entry_64.S
+++ b/arch/powerpc/kernel/entry_64.S
@@ -584,9 +584,34 @@ BEGIN_FTR_SECTION
ld r7,DSCR_DEFAULT@toc(2)
ld r0,THREAD_DSCR(r4)
cmpwi r6,0
+ li r8, FSCR_DSCR
bne 1f
ld r0,0(r7)
-1: cmpd r0,r25
+ b 3f
+1:
+ BEGIN_FTR_SECTION_NESTED(70)
+ mfspr r6, SPRN_FSCR
+ or r6, r6, r8
+ mtspr SPRN_FSCR, r6
+ BEGIN_FTR_SECTION_NESTED(69)
+ mfspr r6, SPRN_HFSCR
+ or r6, r6, r8
+ mtspr SPRN_HFSCR, r6
+ END_FTR_SECTION_NESTED(CPU_FTR_HVMODE, CPU_FTR_HVMODE, 69)
+ b 4f
+ END_FTR_SECTION_NESTED(CPU_FTR_ARCH_207S, CPU_FTR_ARCH_207S, 70)
+3:
+ BEGIN_FTR_SECTION_NESTED(70)
+ mfspr r6, SPRN_FSCR
+ andc r6, r6, r8
+ mtspr SPRN_FSCR, r6
+ BEGIN_FTR_SECTION_NESTED(69)
+ mfspr r6, SPRN_HFSCR
+ andc r6, r6, r8
+ mtspr SPRN_HFSCR, r6
+ END_FTR_SECTION_NESTED(CPU_FTR_HVMODE, CPU_FTR_HVMODE, 69)
+ END_FTR_SECTION_NESTED(CPU_FTR_ARCH_207S, CPU_FTR_ARCH_207S, 70)
+4: cmpd r0,r25
beq 2f
mtspr SPRN_DSCR,r0
2:
--- a/arch/powerpc/kernel/traps.c
+++ b/arch/powerpc/kernel/traps.c
@@ -44,9 +44,7 @@
#include <asm/machdep.h>
#include <asm/rtas.h>
#include <asm/pmc.h>
-#ifdef CONFIG_PPC32
#include <asm/reg.h>
-#endif
#ifdef CONFIG_PMAC_BACKLIGHT
#include <asm/backlight.h>
#endif
@@ -1282,43 +1280,54 @@ void vsx_unavailable_exception(struct pt
die("Unrecoverable VSX Unavailable Exception", regs, SIGABRT);
}
+#ifdef CONFIG_PPC64
void facility_unavailable_exception(struct pt_regs *regs)
{
static char *facility_strings[] = {
- "FPU",
- "VMX/VSX",
- "DSCR",
- "PMU SPRs",
- "BHRB",
- "TM",
- "AT",
- "EBB",
- "TAR",
+ [FSCR_FP_LG] = "FPU",
+ [FSCR_VECVSX_LG] = "VMX/VSX",
+ [FSCR_DSCR_LG] = "DSCR",
+ [FSCR_PM_LG] = "PMU SPRs",
+ [FSCR_BHRB_LG] = "BHRB",
+ [FSCR_TM_LG] = "TM",
+ [FSCR_EBB_LG] = "EBB",
+ [FSCR_TAR_LG] = "TAR",
};
- char *facility, *prefix;
+ char *facility = "unknown";
u64 value;
+ u8 status;
+ bool hv;
- if (regs->trap == 0xf60) {
- value = mfspr(SPRN_FSCR);
- prefix = "";
- } else {
+ hv = (regs->trap == 0xf80);
+ if (hv)
value = mfspr(SPRN_HFSCR);
- prefix = "Hypervisor ";
+ else
+ value = mfspr(SPRN_FSCR);
+
+ status = value >> 56;
+ if (status == FSCR_DSCR_LG) {
+ /* User is acessing the DSCR. Set the inherit bit and allow
+ * the user to set it directly in future by setting via the
+ * H/FSCR DSCR bit.
+ */
+ current->thread.dscr_inherit = 1;
+ if (hv)
+ mtspr(SPRN_HFSCR, value | HFSCR_DSCR);
+ else
+ mtspr(SPRN_FSCR, value | FSCR_DSCR);
+ return;
}
- value = value >> 56;
+ if ((status < ARRAY_SIZE(facility_strings)) &&
+ facility_strings[status])
+ facility = facility_strings[status];
/* We restore the interrupt state now */
if (!arch_irq_disabled_regs(regs))
local_irq_enable();
- if (value < ARRAY_SIZE(facility_strings))
- facility = facility_strings[value];
- else
- facility = "unknown";
-
pr_err("%sFacility '%s' unavailable, exception at 0x%lx, MSR=%lx\n",
- prefix, facility, regs->nip, regs->msr);
+ hv ? "Hypervisor " : "", facility, regs->nip, regs->msr);
if (user_mode(regs)) {
_exception(SIGILL, regs, ILL_ILLOPC, regs->nip);
@@ -1327,6 +1336,7 @@ void facility_unavailable_exception(stru
die("Unexpected facility unavailable exception", regs, SIGABRT);
}
+#endif
#ifdef CONFIG_PPC_TRANSACTIONAL_MEM
Patches currently in stable-queue which might be from mikey@xxxxxxxxxxx are
queue-3.10/powerpc-tm-fix-context-switching-tar-ppr-and-dscr-sprs.patch
queue-3.10/powerpc-fix-hypervisor-facility-unavaliable-vector-number.patch
queue-3.10/powerpc-rework-setting-up-h-fscr-bit-definitions.patch
queue-3.10/powerpc-on-powernv-enable-ppc_denormalisation-by-default.patch
queue-3.10/powerpc-save-the-tar-register-earlier.patch
queue-3.10/powerpc-fix-context-switch-dscr-on-power8.patch
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