[PATCH v7 05/10] target/ppc: Move patching nip from exception handler to helper_scv

From: BALATON Zoltan <balaton@eik.bme.hu>
To: qemu-devel@nongnu.org, qemu-ppc@nongnu.org
Cc: Nicholas Piggin <npiggin@gmail.com>,
	Daniel Henrique Barboza <danielhb413@gmail.com>,
	clg@kaod.org
Subject: [PATCH v7 05/10] target/ppc: Move patching nip from exception handler to helper_scv
Date: Tue, 27 Feb 2024 16:08:05 +0100 (CET)	[thread overview]
Message-ID: <4c813b27498fac293b1284f78bdbb6b94286f3c3.1709045654.git.balaton@eik.bme.hu> (raw)
In-Reply-To: <cover.1709045654.git.balaton@eik.bme.hu>

From: Nicholas Piggin <npiggin@gmail.com>

Unlike sc, for scv a facility unavailable interrupt must be generated
if FSCR[SCV]=0 so we can't raise the exception with nip set to next
instruction but we can move advancing nip if the FSCR check passes to
helper_scv so the exception handler does not need to change it.

[balaton: added commit message]
Signed-off-by: BALATON Zoltan <balaton@eik.bme.hu>
---
 target/ppc/excp_helper.c | 2 +-
 target/ppc/translate.c   | 6 +++++-
 2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/target/ppc/excp_helper.c b/target/ppc/excp_helper.c
index f1e62d9878..6cf4542e7e 100644
--- a/target/ppc/excp_helper.c
+++ b/target/ppc/excp_helper.c
@@ -1414,7 +1414,6 @@ static void powerpc_excp_books(PowerPCCPU *cpu, int excp)
     case POWERPC_EXCP_SYSCALL_VECTORED: /* scv exception                     */
         lev = env->error_code;
         dump_syscall(env);
-        env->nip += 4;
         new_msr |= env->msr & ((target_ulong)1 << MSR_EE);
         new_msr |= env->msr & ((target_ulong)1 << MSR_RI);
 
@@ -2537,6 +2536,7 @@ void helper_ppc_maybe_interrupt(CPUPPCState *env)
 void helper_scv(CPUPPCState *env, uint32_t lev)
 {
     if (env->spr[SPR_FSCR] & (1ull << FSCR_SCV)) {
+        env->nip += 4;
         raise_exception_err(env, POWERPC_EXCP_SYSCALL_VECTORED, lev);
     } else {
         raise_exception_err(env, POWERPC_EXCP_FU, FSCR_IC_SCV);
diff --git a/target/ppc/translate.c b/target/ppc/translate.c
index a3ac8c3d0e..1d69283c80 100644
--- a/target/ppc/translate.c
+++ b/target/ppc/translate.c
@@ -4590,7 +4590,11 @@ static void gen_scv(DisasContext *ctx)
 {
     uint32_t lev = (ctx->opcode >> 5) & 0x7F;
 
-    /* Set the PC back to the faulting instruction. */
+    /*
+     * Set the PC back to the scv instruction (unlike sc), because a facility
+     * unavailable interrupt must be generated if FSCR[SCV]=0. The helper
+     * advances nip if the FSCR check passes.
+     */
     gen_update_nip(ctx, ctx->cia);
     gen_helper_scv(tcg_env, tcg_constant_i32(lev));
 
-- 
2.30.9


