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Re: [PATCH v2] target/ppc: Fix BookE debug interrupt generation

From: Lucas Mateus Martins Araujo e Castro
Subject: Re: [PATCH v2] target/ppc: Fix BookE debug interrupt generation
Date: Mon, 25 Apr 2022 11:16:01 -0300
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.7.0

On 20/04/2022 22:17, Bin Meng wrote:
From: Bin Meng <bin.meng@windriver.com>

Per E500 core reference manual [1], chapter 8.4.4 "Branch Taken Debug
Event" and chapter 8.4.5 "Instruction Complete Debug Event":

  "A branch taken debug event occurs if both MSR[DE] and DBCR0[BRT]
  are set ... Branch taken debug events are not recognized if MSR[DE]
  is cleared when the branch instruction executes."

  "An instruction complete debug event occurs when any instruction
  completes execution so long as MSR[DE] and DBCR0[ICMP] are both
  set ... Instruction complete debug events are not recognized if
  MSR[DE] is cleared at the time of the instruction execution."

Current codes do not check MSR.DE bit before setting HFLAGS_SE and
HFLAGS_BE flag, which would cause the immediate debug interrupt to
be generated, e.g.: when DBCR0.ICMP bit is set by guest software
and MSR.DE is not set.

[1] https://www.nxp.com/docs/en/reference-manual/E500CORERM.pdf

Signed-off-by: Bin Meng <bin.meng@windriver.com>

Changes in v2:
- update commit message to use E500CORERM instead of PowerISA 2.07

 target/ppc/helper_regs.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/target/ppc/helper_regs.c b/target/ppc/helper_regs.c
index 9a691d6833..77bc57415c 100644
--- a/target/ppc/helper_regs.c
+++ b/target/ppc/helper_regs.c
@@ -63,10 +63,10 @@ static uint32_t hreg_compute_hflags_value(CPUPPCState *env)

     if (ppc_flags & POWERPC_FLAG_DE) {
         target_ulong dbcr0 = env->spr[SPR_BOOKE_DBCR0];
-        if (dbcr0 & DBCR0_ICMP) {
+        if ((dbcr0 & DBCR0_ICMP) && msr_de) {
There was a discussion some time ago that was better to avoid hidden uses of *env, so it may be better to change msr_de to ((env->msr >> MSR_DE) & 1) or to (env->msr & BIT_ULL(MSR_DE))
             hflags |= 1 << HFLAGS_SE;
-        if (dbcr0 & DBCR0_BRT) {
+        if ((dbcr0 & DBCR0_BRT) && msr_de) {
Here as well
             hflags |= 1 << HFLAGS_BE;
     } else {

Apart from that,
Reviewed-by: Lucas Mateus Castro <lucas.araujo@eldorado.org.br>
Lucas Mateus M. Araujo e Castro
Instituto de Pesquisas ELDORADO
Departamento Computação Embarcada
Analista de Software Trainee
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