Re: [PATCH for-5.0] hw/ppc: Take QEMU lock when calling ppc_dcr_read/write()

[David Gibson]

On Sun, Mar 22, 2020 at 07:22:58PM +0000, Peter Maydell wrote:
> The ppc_dcr_read() and ppc_dcr_write() functions call into callbacks
> in device code, so we need to hold the QEMU iothread lock while
> calling them.  This is the case already for the callsites in
> kvmppc_handle_dcr_read/write(), but we must also take the lock when
> calling the helpers from TCG.
> 
> This fixes a bug where attempting to initialise the PPC405EP
> SDRAM will cause an assertion when sdram_map_bcr() attempts
> to remap memory regions.
> 
> Reported-by: Amit Lazar <address@hidden>
> Signed-off-by: Peter Maydell <address@hidden>

Applied to ppc-for-5.0.

> ---
> Amit reported this bug via IRC.
> 
>  target/ppc/timebase_helper.c | 40 +++++++++++++++++++++++-------------
>  1 file changed, 26 insertions(+), 14 deletions(-)
> 
> diff --git a/target/ppc/timebase_helper.c b/target/ppc/timebase_helper.c
> index 703bd9ed18b..d16360ab667 100644
> --- a/target/ppc/timebase_helper.c
> +++ b/target/ppc/timebase_helper.c
> @@ -21,6 +21,7 @@
>  #include "exec/helper-proto.h"
>  #include "exec/exec-all.h"
>  #include "qemu/log.h"
> +#include "qemu/main-loop.h"
>  
>  
> /*****************************************************************************/
>  /* SPR accesses */
> @@ -167,13 +168,19 @@ target_ulong helper_load_dcr(CPUPPCState *env, 
> target_ulong dcrn)
>          raise_exception_err_ra(env, POWERPC_EXCP_PROGRAM,
>                                 POWERPC_EXCP_INVAL |
>                                 POWERPC_EXCP_INVAL_INVAL, GETPC());
> -    } else if (unlikely(ppc_dcr_read(env->dcr_env,
> -                                     (uint32_t)dcrn, &val) != 0)) {
> -        qemu_log_mask(LOG_GUEST_ERROR, "DCR read error %d %03x\n",
> -                      (uint32_t)dcrn, (uint32_t)dcrn);
> -        raise_exception_err_ra(env, POWERPC_EXCP_PROGRAM,
> -                               POWERPC_EXCP_INVAL |
> -                               POWERPC_EXCP_PRIV_REG, GETPC());
> +    } else {
> +        int ret;
> +
> +        qemu_mutex_lock_iothread();
> +        ret = ppc_dcr_read(env->dcr_env, (uint32_t)dcrn, &val);
> +        qemu_mutex_unlock_iothread();
> +        if (unlikely(ret != 0)) {
> +            qemu_log_mask(LOG_GUEST_ERROR, "DCR read error %d %03x\n",
> +                          (uint32_t)dcrn, (uint32_t)dcrn);
> +            raise_exception_err_ra(env, POWERPC_EXCP_PROGRAM,
> +                                   POWERPC_EXCP_INVAL |
> +                                   POWERPC_EXCP_PRIV_REG, GETPC());
> +        }
>      }
>      return val;
>  }
> @@ -185,12 +192,17 @@ void helper_store_dcr(CPUPPCState *env, target_ulong 
> dcrn, target_ulong val)
>          raise_exception_err_ra(env, POWERPC_EXCP_PROGRAM,
>                                 POWERPC_EXCP_INVAL |
>                                 POWERPC_EXCP_INVAL_INVAL, GETPC());
> -    } else if (unlikely(ppc_dcr_write(env->dcr_env, (uint32_t)dcrn,
> -                                      (uint32_t)val) != 0)) {
> -        qemu_log_mask(LOG_GUEST_ERROR, "DCR write error %d %03x\n",
> -                      (uint32_t)dcrn, (uint32_t)dcrn);
> -        raise_exception_err_ra(env, POWERPC_EXCP_PROGRAM,
> -                               POWERPC_EXCP_INVAL |
> -                               POWERPC_EXCP_PRIV_REG, GETPC());
> +    } else {
> +        int ret;
> +        qemu_mutex_lock_iothread();
> +        ret = ppc_dcr_write(env->dcr_env, (uint32_t)dcrn, (uint32_t)val);
> +        qemu_mutex_unlock_iothread();
> +        if (unlikely(ret != 0)) {
> +            qemu_log_mask(LOG_GUEST_ERROR, "DCR write error %d %03x\n",
> +                          (uint32_t)dcrn, (uint32_t)dcrn);
> +            raise_exception_err_ra(env, POWERPC_EXCP_PROGRAM,
> +                                   POWERPC_EXCP_INVAL |
> +                                   POWERPC_EXCP_PRIV_REG, GETPC());
> +        }
>      }
>  }

-- 
David Gibson                    | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au  | minimalist, thank you.  NOT _the_ _other_
                                | _way_ _around_!
http://www.ozlabs.org/~dgibson

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