* [PATCH] target/riscv: Do not hide Sstc CSRs from gdbstub
@ 2026-05-25 2:42 Zephyr Li
2026-05-25 4:29 ` Chao Liu
` (2 more replies)
0 siblings, 3 replies; 4+ messages in thread
From: Zephyr Li @ 2026-05-25 2:42 UTC (permalink / raw)
To: qemu-devel
Cc: qemu-riscv, palmer, alistair.francis, liwei1518, zhiwei_liu,
chao.liu.zevorn, daniel.barboza
The Sstc predicate currently checks both ext_sstc and rdtime_fn. This
causes the gdbstub CSR XML generation to skip Sstc CSRs when rdtime_fn
has not been initialized yet, even if the CPU supports Sstc.
As a result, GDB reports $stimecmp as void with a CPU that exposes the
sstc extension.
Only use ext_sstc for the early existence check, and keep the rdtime_fn
check for non-debugger accesses.
Resolves: https://gitlab.com/qemu-project/qemu/-/work_items/3496
Signed-off-by: Zephyr Li <fritchleybohrer@gmail.com>
---
Testing:
Start QEMU with:
qemu-system-riscv64 -M virt,aclint=on -cpu max,sstc=true -s -S -nographic
Before:
(gdb) p $stimecmp
$1 = void
After:
(gdb) p $stimecmp
$1 = 0
target/riscv/csr.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/target/riscv/csr.c b/target/riscv/csr.c
index da366cf562..c17df147f7 100644
--- a/target/riscv/csr.c
+++ b/target/riscv/csr.c
@@ -586,7 +586,7 @@ static RISCVException sstc(CPURISCVState *env, int csrno)
{
bool hmode_check = false;
- if (!riscv_cpu_cfg(env)->ext_sstc || !env->rdtime_fn) {
+ if (!riscv_cpu_cfg(env)->ext_sstc) {
return RISCV_EXCP_ILLEGAL_INST;
}
@@ -603,6 +603,10 @@ static RISCVException sstc(CPURISCVState *env, int csrno)
return RISCV_EXCP_NONE;
}
+ if (!env->rdtime_fn) {
+ return RISCV_EXCP_ILLEGAL_INST;
+ }
+
if (env->priv == PRV_M) {
return RISCV_EXCP_NONE;
}
--
2.43.0
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH] target/riscv: Do not hide Sstc CSRs from gdbstub
2026-05-25 2:42 [PATCH] target/riscv: Do not hide Sstc CSRs from gdbstub Zephyr Li
@ 2026-05-25 4:29 ` Chao Liu
2026-05-27 0:05 ` Alistair Francis
2026-05-27 0:09 ` Alistair Francis
2 siblings, 0 replies; 4+ messages in thread
From: Chao Liu @ 2026-05-25 4:29 UTC (permalink / raw)
To: Zephyr Li
Cc: qemu-devel, qemu-riscv, palmer, alistair.francis, liwei1518,
zhiwei_liu, daniel.barboza
On Mon, May 25, 2026 at 10:42:20AM +0800, Zephyr Li wrote:
> The Sstc predicate currently checks both ext_sstc and rdtime_fn. This
> causes the gdbstub CSR XML generation to skip Sstc CSRs when rdtime_fn
> has not been initialized yet, even if the CPU supports Sstc.
>
> As a result, GDB reports $stimecmp as void with a CPU that exposes the
> sstc extension.
>
> Only use ext_sstc for the early existence check, and keep the rdtime_fn
> check for non-debugger accesses.
>
> Resolves: https://gitlab.com/qemu-project/qemu/-/work_items/3496
> Signed-off-by: Zephyr Li <fritchleybohrer@gmail.com>
Reviewed-by: Chao Liu <chao.liu.zevorn@gmail.com>
> ---
>
> Testing:
> Start QEMU with:
> qemu-system-riscv64 -M virt,aclint=on -cpu max,sstc=true -s -S -nographic
>
> Before:
> (gdb) p $stimecmp
> $1 = void
>
> After:
> (gdb) p $stimecmp
> $1 = 0
>
> target/riscv/csr.c | 6 +++++-
> 1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/target/riscv/csr.c b/target/riscv/csr.c
> index da366cf562..c17df147f7 100644
> --- a/target/riscv/csr.c
> +++ b/target/riscv/csr.c
> @@ -586,7 +586,7 @@ static RISCVException sstc(CPURISCVState *env, int csrno)
> {
> bool hmode_check = false;
>
> - if (!riscv_cpu_cfg(env)->ext_sstc || !env->rdtime_fn) {
> + if (!riscv_cpu_cfg(env)->ext_sstc) {
> return RISCV_EXCP_ILLEGAL_INST;
> }
>
> @@ -603,6 +603,10 @@ static RISCVException sstc(CPURISCVState *env, int csrno)
> return RISCV_EXCP_NONE;
> }
>
> + if (!env->rdtime_fn) {
> + return RISCV_EXCP_ILLEGAL_INST;
> + }
> +
> if (env->priv == PRV_M) {
> return RISCV_EXCP_NONE;
> }
> --
> 2.43.0
>
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] target/riscv: Do not hide Sstc CSRs from gdbstub
2026-05-25 2:42 [PATCH] target/riscv: Do not hide Sstc CSRs from gdbstub Zephyr Li
2026-05-25 4:29 ` Chao Liu
@ 2026-05-27 0:05 ` Alistair Francis
2026-05-27 0:09 ` Alistair Francis
2 siblings, 0 replies; 4+ messages in thread
From: Alistair Francis @ 2026-05-27 0:05 UTC (permalink / raw)
To: fritchleybohrer@gmail.com, qemu-devel@nongnu.org
Cc: qemu-riscv@nongnu.org, palmer@dabbelt.com,
daniel.barboza@oss.qualcomm.com, chao.liu.zevorn@gmail.com,
liwei1518@gmail.com, zhiwei_liu@linux.alibaba.com
On Mon, 2026-05-25 at 10:42 +0800, Zephyr Li wrote:
> The Sstc predicate currently checks both ext_sstc and rdtime_fn. This
> causes the gdbstub CSR XML generation to skip Sstc CSRs when
> rdtime_fn
> has not been initialized yet, even if the CPU supports Sstc.
>
> As a result, GDB reports $stimecmp as void with a CPU that exposes
> the
> sstc extension.
>
> Only use ext_sstc for the early existence check, and keep the
> rdtime_fn
> check for non-debugger accesses.
>
> Resolves: https://gitlab.com/qemu-project/qemu/-/work_items/3496
> Signed-off-by: Zephyr Li <fritchleybohrer@gmail.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Alistair
> ---
>
> Testing:
> Start QEMU with:
> qemu-system-riscv64 -M virt,aclint=on -cpu max,sstc=true -s -
> S -nographic
>
> Before:
> (gdb) p $stimecmp
> $1 = void
>
> After:
> (gdb) p $stimecmp
> $1 = 0
>
> target/riscv/csr.c | 6 +++++-
> 1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/target/riscv/csr.c b/target/riscv/csr.c
> index da366cf562..c17df147f7 100644
> --- a/target/riscv/csr.c
> +++ b/target/riscv/csr.c
> @@ -586,7 +586,7 @@ static RISCVException sstc(CPURISCVState *env,
> int csrno)
> {
> bool hmode_check = false;
>
> - if (!riscv_cpu_cfg(env)->ext_sstc || !env->rdtime_fn) {
> + if (!riscv_cpu_cfg(env)->ext_sstc) {
> return RISCV_EXCP_ILLEGAL_INST;
> }
>
> @@ -603,6 +603,10 @@ static RISCVException sstc(CPURISCVState *env,
> int csrno)
> return RISCV_EXCP_NONE;
> }
>
> + if (!env->rdtime_fn) {
> + return RISCV_EXCP_ILLEGAL_INST;
> + }
> +
> if (env->priv == PRV_M) {
> return RISCV_EXCP_NONE;
> }
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] target/riscv: Do not hide Sstc CSRs from gdbstub
2026-05-25 2:42 [PATCH] target/riscv: Do not hide Sstc CSRs from gdbstub Zephyr Li
2026-05-25 4:29 ` Chao Liu
2026-05-27 0:05 ` Alistair Francis
@ 2026-05-27 0:09 ` Alistair Francis
2 siblings, 0 replies; 4+ messages in thread
From: Alistair Francis @ 2026-05-27 0:09 UTC (permalink / raw)
To: fritchleybohrer@gmail.com, qemu-devel@nongnu.org
Cc: qemu-riscv@nongnu.org, palmer@dabbelt.com,
daniel.barboza@oss.qualcomm.com, chao.liu.zevorn@gmail.com,
liwei1518@gmail.com, zhiwei_liu@linux.alibaba.com
On Mon, 2026-05-25 at 10:42 +0800, Zephyr Li wrote:
> The Sstc predicate currently checks both ext_sstc and rdtime_fn. This
> causes the gdbstub CSR XML generation to skip Sstc CSRs when
> rdtime_fn
> has not been initialized yet, even if the CPU supports Sstc.
>
> As a result, GDB reports $stimecmp as void with a CPU that exposes
> the
> sstc extension.
>
> Only use ext_sstc for the early existence check, and keep the
> rdtime_fn
> check for non-debugger accesses.
>
> Resolves: https://gitlab.com/qemu-project/qemu/-/work_items/3496
> Signed-off-by: Zephyr Li <fritchleybohrer@gmail.com>
Thanks!
Applied to riscv-to-apply.next
Alistair
> ---
>
> Testing:
> Start QEMU with:
> qemu-system-riscv64 -M virt,aclint=on -cpu max,sstc=true -s -
> S -nographic
>
> Before:
> (gdb) p $stimecmp
> $1 = void
>
> After:
> (gdb) p $stimecmp
> $1 = 0
>
> target/riscv/csr.c | 6 +++++-
> 1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/target/riscv/csr.c b/target/riscv/csr.c
> index da366cf562..c17df147f7 100644
> --- a/target/riscv/csr.c
> +++ b/target/riscv/csr.c
> @@ -586,7 +586,7 @@ static RISCVException sstc(CPURISCVState *env,
> int csrno)
> {
> bool hmode_check = false;
>
> - if (!riscv_cpu_cfg(env)->ext_sstc || !env->rdtime_fn) {
> + if (!riscv_cpu_cfg(env)->ext_sstc) {
> return RISCV_EXCP_ILLEGAL_INST;
> }
>
> @@ -603,6 +603,10 @@ static RISCVException sstc(CPURISCVState *env,
> int csrno)
> return RISCV_EXCP_NONE;
> }
>
> + if (!env->rdtime_fn) {
> + return RISCV_EXCP_ILLEGAL_INST;
> + }
> +
> if (env->priv == PRV_M) {
> return RISCV_EXCP_NONE;
> }
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2026-05-27 0:09 UTC | newest]
Thread overview: 4+ messages (download: mbox.gz follow: Atom feed
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2026-05-25 2:42 [PATCH] target/riscv: Do not hide Sstc CSRs from gdbstub Zephyr Li
2026-05-25 4:29 ` Chao Liu
2026-05-27 0:05 ` Alistair Francis
2026-05-27 0:09 ` Alistair Francis
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