target/loongarch: Fix the CSRRD CPUID instruction on big endian hosts

The test in tests/avocado/machine_loongarch.py is currently failing
on big endian hosts like s390x. By comparing the traces between running
the QEMU_EFI.fd bios on a s390x and on a x86 host, it's quickly obvious
that the CSRRD instruction for the CPUID is behaving differently. And
indeed: The code currently does a long read (i.e. 64 bit) from the
address that points to the CPUState->cpu_index field (with tcg_gen_ld_tl()
in the trans_csrrd() function). But this cpu_index field is only an "int"
(i.e. 32 bit). While this dirty pointer magic works on little endian hosts,
it of course fails on big endian hosts. Fix it by using a proper helper
function instead.

Signed-off-by: Thomas Huth <thuth@redhat.com>
---
 Note: There is another bug preventing tests/avocado/machine_loongarch.py
 from working correctly on big endian hosts (Linux fails to run the shell)
 but that problem is harder to debug since it happens way later in the boot
 process...

 target/loongarch/cpu.h                             | 1 +
 target/loongarch/helper.h                          | 1 +
 target/loongarch/csr_helper.c                      | 9 +++++++++
 target/loongarch/insn_trans/trans_privileged.c.inc | 8 +-------
 4 files changed, 12 insertions(+), 7 deletions(-)

在 2023/7/21 上午1:53, Thomas Huth 写道:
> The test in tests/avocado/machine_loongarch.py is currently failing
> on big endian hosts like s390x. By comparing the traces between running
> the QEMU_EFI.fd bios on a s390x and on a x86 host, it's quickly obvious
> that the CSRRD instruction for the CPUID is behaving differently. And
> indeed: The code currently does a long read (i.e. 64 bit) from the
> address that points to the CPUState->cpu_index field (with tcg_gen_ld_tl()
> in the trans_csrrd() function). But this cpu_index field is only an "int"
> (i.e. 32 bit). While this dirty pointer magic works on little endian hosts,
> it of course fails on big endian hosts. Fix it by using a proper helper
> function instead.
> 
> Signed-off-by: Thomas Huth <thuth@redhat.com>
> ---
>   Note: There is another bug preventing tests/avocado/machine_loongarch.py
>   from working correctly on big endian hosts (Linux fails to run the shell)
>   but that problem is harder to debug since it happens way later in the boot
>   process...
> 
>   target/loongarch/cpu.h                             | 1 +
>   target/loongarch/helper.h                          | 1 +
>   target/loongarch/csr_helper.c                      | 9 +++++++++
>   target/loongarch/insn_trans/trans_privileged.c.inc | 8 +-------
>   4 files changed, 12 insertions(+), 7 deletions(-)
> 

Reviewed-by: Song Gao <gaosong@loongson.cn>

Thanks.
Song Gao

> diff --git a/target/loongarch/cpu.h b/target/loongarch/cpu.h
> index ed04027af1..fa371ca8ba 100644
> --- a/target/loongarch/cpu.h
> +++ b/target/loongarch/cpu.h
> @@ -342,6 +342,7 @@ typedef struct CPUArchState {
>       uint64_t CSR_DBG;
>       uint64_t CSR_DERA;
>       uint64_t CSR_DSAVE;
> +    uint64_t CSR_CPUID;
>   
>   #ifndef CONFIG_USER_ONLY
>       LoongArchTLB  tlb[LOONGARCH_TLB_MAX];
> diff --git a/target/loongarch/helper.h b/target/loongarch/helper.h
> index b9de77d926..ffb1e0b0bf 100644
> --- a/target/loongarch/helper.h
> +++ b/target/loongarch/helper.h
> @@ -98,6 +98,7 @@ DEF_HELPER_1(rdtime_d, i64, env)
>   #ifndef CONFIG_USER_ONLY
>   /* CSRs helper */
>   DEF_HELPER_1(csrrd_pgd, i64, env)
> +DEF_HELPER_1(csrrd_cpuid, i64, env)
>   DEF_HELPER_1(csrrd_tval, i64, env)
>   DEF_HELPER_2(csrwr_estat, i64, env, tl)
>   DEF_HELPER_2(csrwr_asid, i64, env, tl)
> diff --git a/target/loongarch/csr_helper.c b/target/loongarch/csr_helper.c
> index 6526367946..55341551a5 100644
> --- a/target/loongarch/csr_helper.c
> +++ b/target/loongarch/csr_helper.c
> @@ -35,6 +35,15 @@ target_ulong helper_csrrd_pgd(CPULoongArchState *env)
>       return v;
>   }
>   
> +target_ulong helper_csrrd_cpuid(CPULoongArchState *env)
> +{
> +    LoongArchCPU *lac = env_archcpu(env);
> +
> +    env->CSR_CPUID = CPU(lac)->cpu_index;
> +
> +    return env->CSR_CPUID;
> +}
> +
>   target_ulong helper_csrrd_tval(CPULoongArchState *env)
>   {
>       LoongArchCPU *cpu = env_archcpu(env);
> diff --git a/target/loongarch/insn_trans/trans_privileged.c.inc b/target/loongarch/insn_trans/trans_privileged.c.inc
> index 02bca7ca23..9c9de090f0 100644
> --- a/target/loongarch/insn_trans/trans_privileged.c.inc
> +++ b/target/loongarch/insn_trans/trans_privileged.c.inc
> @@ -99,13 +99,7 @@ static const CSRInfo csr_info[] = {
>       CSR_OFF(PWCH),
>       CSR_OFF(STLBPS),
>       CSR_OFF(RVACFG),
> -    [LOONGARCH_CSR_CPUID] = {
> -        .offset = (int)offsetof(CPUState, cpu_index)
> -                  - (int)offsetof(LoongArchCPU, env),
> -        .flags = CSRFL_READONLY,
> -        .readfn = NULL,
> -        .writefn = NULL
> -    },
> +    CSR_OFF_FUNCS(CPUID, CSRFL_READONLY, gen_helper_csrrd_cpuid, NULL),
>       CSR_OFF_FLAGS(PRCFG1, CSRFL_READONLY),
>       CSR_OFF_FLAGS(PRCFG2, CSRFL_READONLY),
>       CSR_OFF_FLAGS(PRCFG3, CSRFL_READONLY),
>