Re: [PATCH v2 03/18] tcg: move qemu_tcg_configure to accel/tcg/tcg-all.c

["Philippe Mathieu-Daudé" <philmd@redhat.com>]

On 12/9/19 4:01 PM, Paolo Bonzini wrote:
> Move everything related to mttcg_enabled in accel/tcg/tcg-all.c,
> which will make even more sense when "thread" becomes a QOM property.
> 
> For now, initializing mttcg_enabled in the instance_init function
> prepares for the next patch, which will only invoke qemu_tcg_configure
> when the command line includes a -accel option.
> 
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>

> ---
>   accel/tcg/tcg-all.c | 85 +++++++++++++++++++++++++++++++++++++++++++++++++++++
>   cpus.c              | 72 ---------------------------------------------
>   2 files changed, 85 insertions(+), 72 deletions(-)
> 
> diff --git a/accel/tcg/tcg-all.c b/accel/tcg/tcg-all.c
> index c59d5b0..78a0ab5 100644
> --- a/accel/tcg/tcg-all.c
> +++ b/accel/tcg/tcg-all.c
> @@ -30,6 +30,11 @@
>   #include "cpu.h"
>   #include "sysemu/cpus.h"
>   #include "qemu/main-loop.h"
> +#include "tcg/tcg.h"
> +#include "include/qapi/error.h"
> +#include "include/qemu/error-report.h"
> +#include "include/hw/boards.h"
> +#include "qemu/option.h"
>   
>   unsigned long tcg_tb_size;
>   
> @@ -58,6 +63,55 @@ static void tcg_handle_interrupt(CPUState *cpu, int mask)
>       }
>   }
>   
> +/*
> + * We default to false if we know other options have been enabled
> + * which are currently incompatible with MTTCG. Otherwise when each
> + * guest (target) has been updated to support:
> + *   - atomic instructions
> + *   - memory ordering primitives (barriers)
> + * they can set the appropriate CONFIG flags in ${target}-softmmu.mak
> + *
> + * Once a guest architecture has been converted to the new primitives
> + * there are two remaining limitations to check.
> + *
> + * - The guest can't be oversized (e.g. 64 bit guest on 32 bit host)
> + * - The host must have a stronger memory order than the guest
> + *
> + * It may be possible in future to support strong guests on weak hosts
> + * but that will require tagging all load/stores in a guest with their
> + * implicit memory order requirements which would likely slow things
> + * down a lot.
> + */
> +
> +static bool check_tcg_memory_orders_compatible(void)
> +{
> +#if defined(TCG_GUEST_DEFAULT_MO) && defined(TCG_TARGET_DEFAULT_MO)
> +    return (TCG_GUEST_DEFAULT_MO & ~TCG_TARGET_DEFAULT_MO) == 0;
> +#else
> +    return false;
> +#endif
> +}
> +
> +static bool default_mttcg_enabled(void)
> +{
> +    if (use_icount || TCG_OVERSIZED_GUEST) {
> +        return false;
> +    } else {
> +#ifdef TARGET_SUPPORTS_MTTCG
> +        return check_tcg_memory_orders_compatible();
> +#else
> +        return false;
> +#endif
> +    }
> +}
> +
> +static void tcg_accel_instance_init(Object *obj)
> +{
> +    TCGState *s = TCG_STATE(obj);
> +
> +    mttcg_enabled = default_mttcg_enabled();
> +}
> +
>   static int tcg_init(MachineState *ms)
>   {
>       tcg_exec_init(tcg_tb_size * 1024 * 1024);
> @@ -65,6 +119,36 @@ static int tcg_init(MachineState *ms)
>       return 0;
>   }
>   
> +void qemu_tcg_configure(QemuOpts *opts, Error **errp)
> +{
> +    const char *t = qemu_opt_get(opts, "thread");
> +    if (!t) {
> +        return;
> +    }
> +    if (strcmp(t, "multi") == 0) {
> +        if (TCG_OVERSIZED_GUEST) {
> +            error_setg(errp, "No MTTCG when guest word size > hosts");
> +        } else if (use_icount) {
> +            error_setg(errp, "No MTTCG when icount is enabled");
> +        } else {
> +#ifndef TARGET_SUPPORTS_MTTCG
> +            warn_report("Guest not yet converted to MTTCG - "
> +                        "you may get unexpected results");
> +#endif
> +            if (!check_tcg_memory_orders_compatible()) {
> +                warn_report("Guest expects a stronger memory ordering "
> +                            "than the host provides");
> +                error_printf("This may cause strange/hard to debug errors\n");
> +            }
> +            mttcg_enabled = true;
> +        }
> +    } else if (strcmp(t, "single") == 0) {
> +        mttcg_enabled = false;
> +    } else {
> +        error_setg(errp, "Invalid 'thread' setting %s", t);
> +    }
> +}
> +
>   static void tcg_accel_class_init(ObjectClass *oc, void *data)
>   {
>       AccelClass *ac = ACCEL_CLASS(oc);
> @@ -78,6 +162,7 @@ static void tcg_accel_class_init(ObjectClass *oc, void *data)
>   static const TypeInfo tcg_accel_type = {
>       .name = TYPE_TCG_ACCEL,
>       .parent = TYPE_ACCEL,
> +    .instance_init = tcg_accel_instance_init,
>       .class_init = tcg_accel_class_init,
>   };
>   
> diff --git a/cpus.c b/cpus.c
> index 63bda15..b472378 100644
> --- a/cpus.c
> +++ b/cpus.c
> @@ -166,78 +166,6 @@ typedef struct TimersState {
>   static TimersState timers_state;
>   bool mttcg_enabled;
>   
> -/*
> - * We default to false if we know other options have been enabled
> - * which are currently incompatible with MTTCG. Otherwise when each
> - * guest (target) has been updated to support:
> - *   - atomic instructions
> - *   - memory ordering primitives (barriers)
> - * they can set the appropriate CONFIG flags in ${target}-softmmu.mak
> - *
> - * Once a guest architecture has been converted to the new primitives
> - * there are two remaining limitations to check.
> - *
> - * - The guest can't be oversized (e.g. 64 bit guest on 32 bit host)
> - * - The host must have a stronger memory order than the guest
> - *
> - * It may be possible in future to support strong guests on weak hosts
> - * but that will require tagging all load/stores in a guest with their
> - * implicit memory order requirements which would likely slow things
> - * down a lot.
> - */
> -
> -static bool check_tcg_memory_orders_compatible(void)
> -{
> -#if defined(TCG_GUEST_DEFAULT_MO) && defined(TCG_TARGET_DEFAULT_MO)
> -    return (TCG_GUEST_DEFAULT_MO & ~TCG_TARGET_DEFAULT_MO) == 0;
> -#else
> -    return false;
> -#endif
> -}
> -
> -static bool default_mttcg_enabled(void)
> -{
> -    if (use_icount || TCG_OVERSIZED_GUEST) {
> -        return false;
> -    } else {
> -#ifdef TARGET_SUPPORTS_MTTCG
> -        return check_tcg_memory_orders_compatible();
> -#else
> -        return false;
> -#endif
> -    }
> -}
> -
> -void qemu_tcg_configure(QemuOpts *opts, Error **errp)
> -{
> -    const char *t = qemu_opt_get(opts, "thread");
> -    if (t) {
> -        if (strcmp(t, "multi") == 0) {
> -            if (TCG_OVERSIZED_GUEST) {
> -                error_setg(errp, "No MTTCG when guest word size > hosts");
> -            } else if (use_icount) {
> -                error_setg(errp, "No MTTCG when icount is enabled");
> -            } else {
> -#ifndef TARGET_SUPPORTS_MTTCG
> -                warn_report("Guest not yet converted to MTTCG - "
> -                            "you may get unexpected results");
> -#endif
> -                if (!check_tcg_memory_orders_compatible()) {
> -                    warn_report("Guest expects a stronger memory ordering "
> -                                "than the host provides");
> -                    error_printf("This may cause strange/hard to debug errors\n");
> -                }
> -                mttcg_enabled = true;
> -            }
> -        } else if (strcmp(t, "single") == 0) {
> -            mttcg_enabled = false;
> -        } else {
> -            error_setg(errp, "Invalid 'thread' setting %s", t);
> -        }
> -    } else {
> -        mttcg_enabled = default_mttcg_enabled();
> -    }
> -}
>   
>   /* The current number of executed instructions is based on what we
>    * originally budgeted minus the current state of the decrementing
>