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authorMichael Neuling <mikey@neuling.org>2013-08-09 17:29:29 +1000
committerBenjamin Herrenschmidt <benh@kernel.crashing.org>2013-08-09 18:07:05 +1000
commit2517617e0de65f8f7cfe75cae745d06b1fa98586 (patch)
treee0350aa1f8260dc0b25ab7adf3b83d7ab0b46060
parent74e400cee6c0266ba2d940ed78d981f1e24a8167 (diff)
powerpc: Fix context switch DSCR on POWER8
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@neuling.org> Cc: <stable@vger.kernel.org> [v3.10] Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
-rw-r--r--arch/powerpc/kernel/entry_64.S27
-rw-r--r--arch/powerpc/kernel/traps.c58
2 files changed, 60 insertions, 25 deletions
diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S
index ab15b8d057a..4674fe647ad 100644
--- 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:
diff --git a/arch/powerpc/kernel/traps.c b/arch/powerpc/kernel/traps.c
index bf33c22e38a..e435bc089ea 100644
--- 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
@@ -1296,43 +1294,54 @@ void vsx_unavailable_exception(struct pt_regs *regs)
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);
@@ -1341,6 +1350,7 @@ void facility_unavailable_exception(struct pt_regs *regs)
die("Unexpected facility unavailable exception", regs, SIGABRT);
}
+#endif
#ifdef CONFIG_PPC_TRANSACTIONAL_MEM