starred/qemu
1
0
Fork 0
mirror of https://github.com/qemu/qemu.git synced 2026-07-08 17:46:10 +00:00
Code Issues 380 Packages Projects Releases Wiki Activity

target/ppc: Expose the TB offset of the guest in QEMU monitor

Browse Source 
When debugging issues in KVM guests, it is sometimes helpful to have a
unified trace log of both guest and host to see where things are going
wrong. Expose the TB (timebase) offset through QEMU monitor to enable
capturing of unified log.

The below steps can be then used for KVM guests to get a unified log:
1. In host
trace-cmd record -e kvm_hv:kvm_guest_enter -e kvm_hv:kvm_guest_exit \
    -C ppc-tb -o trace_host.dat

2. In guest
trace-cmd record -e powerpc:hcall_entry -e powerpc:hcall_exit -C ppc-tb \
    --ts-offset <TB offset from QEMU monitor> -o trace_guest.dat

  NOTE: The TB offset would be reported as a negative number in QEMU
  monitor. For this step, the minus sign must be ignored.

3. Transfer the guest logs to the host with scp/rsync

4. Unify the logs
trace-cmd report -i trace_host.dat -i trace_guest.dat > combined_log

In case of TCG guests, the TB offset would be
reported as 0 since the offset logic is not applicable in this case.

Tested-by: Amit Machhiwal <amachhiw@linux.ibm.com>
Reviewed-by: Amit Machhiwal <amachhiw@linux.ibm.com>
Reviewed-by: Vaibhav Jain <vaibhav@linux.ibm.com>
Signed-off-by: Gautam Menghani <gautam@linux.ibm.com>
Tested-by: Sneh Shikha Yadav <syadav@linux.ibm.com>
Link: https://lore.kernel.org/qemu-devel/20260629052602.78276-1-gautam@linux.ibm.com
Signed-off-by: Harsh Prateek Bora <harshpb@linux.ibm.com>
This commit is contained in:
Gautam Menghani
2026-06-29 10:56:01 +05:30
committed by Harsh Prateek Bora
parent ea87cc5e3c
commit feeef57ca0
3 changed files with 9 additions and 2 deletions
Download Patch File Download Diff File Expand all files Collapse all files

5
hw/ppc/ppc.c
View File

@@ -515,6 +515,11 @@ uint64_t cpu_ppc_get_tb(ppc_tb_t *tb_env, uint64_t vmclk, int64_t tb_offset)
return ns_to_tb(tb_env->tb_freq, vmclk) + tb_offset;
}
int64_t cpu_ppc_load_tb_offset(CPUPPCState *env)
{
return env->tb_env->tb_offset;
}
uint64_t cpu_ppc_load_tbl (CPUPPCState *env)
{
ppc_tb_t *tb_env = env->tb_env;

1
target/ppc/cpu.h
View File

@@ -1693,6 +1693,7 @@ void cpu_ppc_store_hdecr(CPUPPCState *env, target_ulong value);
void cpu_ppc_store_tbu40(CPUPPCState *env, uint64_t value);
uint64_t cpu_ppc_load_purr(CPUPPCState *env);
void cpu_ppc_store_purr(CPUPPCState *env, uint64_t value);
int64_t cpu_ppc_load_tb_offset(CPUPPCState *env);
#if !defined(CONFIG_USER_ONLY)
target_ulong load_40x_pit(CPUPPCState *env);
void store_40x_pit(CPUPPCState *env, target_ulong val);

5
target/ppc/cpu_init.c
View File

@@ -7620,8 +7620,9 @@ void ppc_cpu_dump_state(CPUState *cs, FILE *f, int flags)
#if !defined(CONFIG_USER_ONLY)
if (env->tb_env) {
qemu_fprintf(f, "TB %08" PRIu32 " %08" PRIu64
" DECR " TARGET_FMT_lu "\n", cpu_ppc_load_tbu(env),
cpu_ppc_load_tbl(env), cpu_ppc_load_decr(env));
" DECR " TARGET_FMT_lu " TB_OFFSET %016" PRId64 "\n",
cpu_ppc_load_tbu(env), cpu_ppc_load_tbl(env),
cpu_ppc_load_decr(env), cpu_ppc_load_tb_offset(env));
}
#else
qemu_fprintf(f, "TB %08" PRIu32 " %08" PRIu64 "\n", cpu_ppc_load_tbu(env),