powerpc: Fix transactional FP/VMX/VSX unavailable handlers

Currently, if a process starts a transaction and then takes an
exception because the FPU, VMX or VSX unit is unavailable to it,
we end up corrupting any FP/VMX/VSX state that was valid before
the interrupt.  For example, if the process starts a transaction
with the FPU available to it but VMX unavailable, and then does
a VMX instruction inside the transaction, the FP state gets
corrupted.

Loading up the desired state generally involves doing a reclaim
and a recheckpoint.  To avoid corrupting already-valid state, we have
to be careful not to reload that state from the thread_struct
between the reclaim and the recheckpoint (since the thread_struct
values are stale by now), and we have to reload that state from
the transact_fp/vr arrays after the recheckpoint to get back the
current transactional values saved there by the reclaim.

Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

1 files changed, 36 insertions, 9 deletions

diff --git a/arch/powerpc/kernel/traps.c b/arch/powerpc/kernel/traps.c
index 26e1358ff0bc..33cd7a0b8e73 100644
--- a/arch/powerpc/kernel/traps.c
+++ b/arch/powerpc/kernel/traps.c
@@ -1416,11 +1416,19 @@ void fp_unavailable_tm(struct pt_regs *regs)
         /* This loads and recheckpoints the FP registers from
          * thread.fpr[].  They will remain in registers after the
          * checkpoint so we don't need to reload them after.
+         * If VMX is in use, the VRs now hold checkpointed values,
+         * so we don't want to load the VRs from the thread_struct.
          */
-        tm_recheckpoint(&current->thread, regs->msr);
+        tm_recheckpoint(&current->thread, MSR_FP);
+
+        /* If VMX is in use, get the transactional values back */
+        if (regs->msr & MSR_VEC) {
+                do_load_up_transact_altivec(&current->thread);
+                /* At this point all the VSX state is loaded, so enable it */
+                regs->msr |= MSR_VSX;
+        }
 }
 
-#ifdef CONFIG_ALTIVEC
 void altivec_unavailable_tm(struct pt_regs *regs)
 {
         /* See the comments in fp_unavailable_tm().  This function operates
@@ -1432,14 +1440,19 @@ void altivec_unavailable_tm(struct pt_regs *regs)
                  regs->nip, regs->msr);
         tm_reclaim_current(TM_CAUSE_FAC_UNAV);
         regs->msr |= MSR_VEC;
-        tm_recheckpoint(&current->thread, regs->msr);
+        tm_recheckpoint(&current->thread, MSR_VEC);
         current->thread.used_vr = 1;
+
+        if (regs->msr & MSR_FP) {
+                do_load_up_transact_fpu(&current->thread);
+                regs->msr |= MSR_VSX;
+        }
 }
-#endif
 
-#ifdef CONFIG_VSX
 void vsx_unavailable_tm(struct pt_regs *regs)
 {
+        unsigned long orig_msr = regs->msr;
+
         /* See the comments in fp_unavailable_tm().  This works similarly,
          * though we're loading both FP and VEC registers in here.
          *
@@ -1451,16 +1464,30 @@ void vsx_unavailable_tm(struct pt_regs *regs)
                  "MSR=%lx\n",
                  regs->nip, regs->msr);
 
+        current->thread.used_vsr = 1;
+
+        /* If FP and VMX are already loaded, we have all the state we need */
+        if ((orig_msr & (MSR_FP | MSR_VEC)) == (MSR_FP | MSR_VEC)) {
+                regs->msr |= MSR_VSX;
+                return;
+        }
+
         /* This reclaims FP and/or VR regs if they're already enabled */
         tm_reclaim_current(TM_CAUSE_FAC_UNAV);
 
         regs->msr |= MSR_VEC | MSR_FP | current->thread.fpexc_mode |
                 MSR_VSX;
-        /* This loads & recheckpoints FP and VRs. */
-        tm_recheckpoint(&current->thread, regs->msr);
-        current->thread.used_vsr = 1;
+
+        /* This loads & recheckpoints FP and VRs; but we have
+         * to be sure not to overwrite previously-valid state.
+         */
+        tm_recheckpoint(&current->thread, regs->msr & ~orig_msr);
+
+        if (orig_msr & MSR_FP)
+                do_load_up_transact_fpu(&current->thread);
+        if (orig_msr & MSR_VEC)
+                do_load_up_transact_altivec(&current->thread);
 }
-#endif
 #endif /* CONFIG_PPC_TRANSACTIONAL_MEM */
 
 void performance_monitor_exception(struct pt_regs *regs)