target/ppc: Move wait instruction to decodetree
Implement wait instruction using decodetree with proper handling of WC and PL fields across different ISA versions. Since the opcode changed between ISA 2.x and 3.x we have defined 2 different decodetree instructions that are handled by the same helper. The changes have been tested by comparing the tcg generated before and after the change for wait instruction. The test was repeated for 2 types of machines: Power10 - which should use the newer wait implementation e500mc - which should use older PPC_WAIT implementation Both generated the same tcg ops with and without the change. Further, with the changes we were able to boot into Fedora distro as well. Signed-off-by: Ojaswin Mujoo <ojaswin@linux.ibm.com> Reviewed-by: Glenn Miles <milesg@linux.ibm.com> Reviewed-by: Amit Machhiwal <amachhiw@linux.ibm.com> Signed-off-by: Chinmay Rath <rathc@linux.ibm.com> Tested-by: Aniket Sahu <asahu1x@linux.ibm.com> Link: https://lore.kernel.org/qemu-devel/20260827133010.278889-18-rathc@linux.ibm.com Signed-off-by: Harsh Prateek Bora <harshpb@linux.ibm.com>
Ojaswin Mujoo committed
Aug 27, 2026 at 18:59 UTC
c07bff60b8fcae5e305c912591732e1b13f5c274
3 files changed
+114
-91
target/ppc/insn32.decode
+15
@@ -1478,6 +1478,21 @@ ISYNC 010011 ----- ----- ----- 0010010110 -
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@XL_bfa ...... bf:3 .. bfa:3 .. ..... ..... ..... .
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MCRF 010011 ... -- ... -- ----- 00000 00000 - @XL_bfa
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+# Wait Instructions
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+
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+# We can use the same X_wait argument set for both WAIT and older ISA2.x
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+# compliant WAIT_2_x. Depending on the version, we may or may not use the
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+# arguments. For more information, check do_wait() helper.
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+
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+&X_wait wc pl
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+@X_wait ...... ..- wc:2 --- pl:2 ----- .......... - &X_wait
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+
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+# According to ISA v3.1, bit 6 and 7 are implementation dependent and "unless
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+# the intention is to use the implementation-dependent field, these bits must be
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+# coded zero". Hence, we code them to 0.
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+WAIT 011111 00-.. ---.. ----- 0000011110 - @X_wait
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+WAIT_ISA_2_X 011111 ---.. ---.. ----- 0000111110 - @X_wait
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+
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# Branch History Rolling Buffer (BHRB) Instructions
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&XFX_bhrbe rt bhrbe
target/ppc/translate.c
-91
@@ -2727,95 +2727,6 @@ static inline void gen_check_tlb_flush(DisasContext *ctx, bool global)
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static inline void gen_check_tlb_flush(DisasContext *ctx, bool global) { }
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#endif
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-/* wait */
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-static void gen_wait(DisasContext *ctx)
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-{
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- uint32_t wc;
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-
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- if (ctx->insns_flags & PPC_WAIT) {
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- /* v2.03-v2.07 define an older incompatible 'wait' encoding. */
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-
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- if (ctx->insns_flags2 & PPC2_PM_ISA206) {
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- /* v2.06 introduced the WC field. WC > 0 may be treated as no-op. */
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- wc = WC(ctx->opcode);
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- } else {
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- wc = 0;
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- }
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-
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- } else if (ctx->insns_flags2 & PPC2_ISA300) {
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- /* v3.0 defines a new 'wait' encoding. */
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- wc = WC(ctx->opcode);
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- if (ctx->insns_flags2 & PPC2_ISA310) {
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- uint32_t pl = PL(ctx->opcode);
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-
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- /* WC 1,2 may be treated as no-op. WC 3 is reserved. */
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- if (wc == 3) {
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- gen_invalid(ctx);
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- return;
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- }
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-
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- /* PL 1-3 are reserved. If WC=2 then the insn is treated as noop. */
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- if (pl > 0 && wc != 2) {
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- gen_invalid(ctx);
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- return;
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- }
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-
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- } else { /* ISA300 */
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- /* WC 1-3 are reserved */
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- if (wc > 0) {
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- gen_invalid(ctx);
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- return;
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- }
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- }
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-
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- } else {
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- warn_report("wait instruction decoded with wrong ISA flags.");
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- gen_invalid(ctx);
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- return;
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- }
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-
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- /*
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- * wait without WC field or with WC=0 waits for an exception / interrupt
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- * to occur.
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- */
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- if (wc == 0) {
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- TCGv_i32 t0 = tcg_constant_i32(1);
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- tcg_gen_st_i32(t0, tcg_env,
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- -offsetof(PowerPCCPU, env) + offsetof(CPUState, halted));
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- /* Stop translation, as the CPU is supposed to sleep from now */
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- gen_exception_nip(ctx, EXCP_HLT, ctx->base.pc_next);
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- }
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-
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- /*
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- * Other wait types must not just wait until an exception occurs because
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- * ignoring their other wake-up conditions could cause a hang.
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- *
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- * For v2.06 and 2.07, wc=1,2,3 are architected but may be implemented as
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- * no-ops.
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- *
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- * wc=1 and wc=3 explicitly allow the instruction to be treated as a no-op.
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- *
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- * wc=2 waits for an implementation-specific condition, such could be
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- * always true, so it can be implemented as a no-op.
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- *
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- * For v3.1, wc=1,2 are architected but may be implemented as no-ops.
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- *
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- * wc=1 (waitrsv) waits for an exception or a reservation to be lost.
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- * Reservation-loss may have implementation-specific conditions, so it
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- * can be implemented as a no-op.
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- *
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- * wc=2 waits for an exception or an amount of time to pass. This
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- * amount is implementation-specific so it can be implemented as a
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- * no-op.
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- *
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- * ISA v3.1 allows for execution to resume "in the rare case of
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- * an implementation-dependent event", so in any case software must
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- * not depend on the architected resumption condition to become
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- * true, so no-op implementations should be architecturally correct
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- * (if suboptimal).
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- */
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-}
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-
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#if defined(TARGET_PPC64)
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static void gen_doze(DisasContext *ctx)
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{
@@ -5184,8 +5095,6 @@ GEN_HANDLER(lswx, 0x1F, 0x15, 0x10, 0x00000001, PPC_STRING),
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GEN_HANDLER(stswi, 0x1F, 0x15, 0x16, 0x00000001, PPC_STRING),
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GEN_HANDLER(stswx, 0x1F, 0x15, 0x14, 0x00000001, PPC_STRING),
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/* ISA v3.0 changed the extended opcode from 62 to 30 */
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-GEN_HANDLER(wait, 0x1F, 0x1E, 0x01, 0x039FF801, PPC_WAIT),
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-GEN_HANDLER_E(wait, 0x1F, 0x1E, 0x00, 0x039CF801, PPC_NONE, PPC2_ISA300),
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GEN_HANDLER(rfi, 0x13, 0x12, 0x01, 0x03FF8001, PPC_FLOW),
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#if defined(TARGET_PPC64)
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GEN_HANDLER(rfid, 0x13, 0x12, 0x00, 0x03FF8001, PPC_64B),
target/ppc/translate/storage-ctrl-impl.c.inc
+99
@@ -270,3 +270,102 @@ static bool do_tlbie(DisasContext *ctx, arg_X_tlbie *a, bool local)
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TRANS_FLAGS(MEM_TLBIE, TLBIE, do_tlbie, false)
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TRANS_FLAGS(MEM_TLBIE, TLBIEL, do_tlbie, true)
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+
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+/*
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+ * Decodetree populates a->wc and a->pl based on ISA v3.1, however they may
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+ * or may not be used based on the ISA:
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+ * For ISA < 2.06 - both wc and pl are ignored
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+ * For ISA == 2.06, 2.07, 3.0 - wc is used and pl is ignored
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+ * For ISA 3.1 - both wc and pl are used
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+ */
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+static bool do_wait(DisasContext *ctx, arg_X_wait *a)
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+{
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+ uint32_t wc;
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+
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+ if (ctx->insns_flags & PPC_WAIT) {
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+ /* v2.03-v2.07 define an older incompatible 'wait' encoding. */
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+
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+ if (ctx->insns_flags2 & PPC2_PM_ISA206) {
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+ /* v2.06 introduced the WC field. WC > 0 may be treated as no-op. */
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+ wc = a->wc;
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+ } else {
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+ wc = 0;
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+ }
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+
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+ } else if (ctx->insns_flags2 & PPC2_ISA300) {
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+ /* v3.0 defines a new 'wait' encoding. */
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+ wc = a->wc;
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+ if (ctx->insns_flags2 & PPC2_ISA310) {
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+ uint32_t pl = a->pl;
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+
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+ /* WC 1,2 may be treated as no-op. WC 3 is reserved. */
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+ if (wc == 3) {
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+ gen_invalid(ctx);
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+ return true;
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+ }
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+
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+ /* PL 1-3 are reserved. If WC=2 then the insn is treated as noop. */
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+ if (pl > 0 && wc != 2) {
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+ gen_invalid(ctx);
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+ return true;
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+ }
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+
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+ } else { /* ISA300 */
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+ /* WC 1-3 are reserved */
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+ if (wc > 0) {
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+ gen_invalid(ctx);
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+ return true;
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+ }
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+ }
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+
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+ } else {
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+ warn_report("wait instruction decoded with wrong ISA flags.");
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+ gen_invalid(ctx);
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+ return true;
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+ }
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+
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+ /*
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+ * wait without WC field or with WC=0 waits for an exception / interrupt
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+ * to occur.
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+ */
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+ if (wc == 0) {
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+ TCGv_i32 t0 = tcg_constant_i32(1);
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+ tcg_gen_st_i32(t0, tcg_env,
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+ -offsetof(PowerPCCPU, env) + offsetof(CPUState, halted));
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+ /* Stop translation, as the CPU is supposed to sleep from now */
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+ gen_exception_nip(ctx, EXCP_HLT, ctx->base.pc_next);
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+ }
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+
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+ /*
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+ * Other wait types must not just wait until an exception occurs because
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+ * ignoring their other wake-up conditions could cause a hang.
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+ *
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+ * For v2.06 and 2.07, wc=1,2,3 are architected but may be implemented as
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+ * no-ops.
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+ *
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+ * wc=1 and wc=3 explicitly allow the instruction to be treated as a no-op.
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+ *
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+ * wc=2 waits for an implementation-specific condition, such could be
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+ * always true, so it can be implemented as a no-op.
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+ *
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+ * For v3.1, wc=1,2 are architected but may be implemented as no-ops.
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+ *
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+ * wc=1 (waitrsv) waits for an exception or a reservation to be lost.
354
+ * Reservation-loss may have implementation-specific conditions, so it
355
+ * can be implemented as a no-op.
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+ *
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+ * wc=2 waits for an exception or an amount of time to pass. This
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+ * amount is implementation-specific so it can be implemented as a
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+ * no-op.
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+ *
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+ * ISA v3.1 allows for execution to resume "in the rare case of
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+ * an implementation-dependent event", so in any case software must
363
+ * not depend on the architected resumption condition to become
364
+ * true, so no-op implementations should be architecturally correct
365
+ * (if suboptimal).
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+ */
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+ return true;
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+}
369
+
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+TRANS_FLAGS(WAIT, WAIT_ISA_2_X, do_wait)
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+TRANS_FLAGS2(ISA300, WAIT, do_wait)