Re: [Qemu-devel] [RFC 4/4] Relevant changes to enable KVM to TCG migration

[Peter Maydell]

On 25 February 2014 16:52, Alvise Rigo <address@hidden> wrote:
> CPUARMState:
> * added adfsr cp register.
> * added aifsr cp register.
> These registers have been added because they are migrated by KVM. This 
> prevents
> the migration from failing when trying to copy their values.

This should be done in a separate patch.

> ARMCPRegInfo:
> * added a pointer to the parent that generated the register (if any).
> * a flag to inform that we have already copied the value of the register:
>   this prevents the register from being overwritten by the parent register
>   value, which could be not set.
>
> helper.c:
> * added mechanism to track the cp register "parent".
> * compare_cpreg_array(): compare the incoming cp registers with the
>   cpreg_list keeping a list of the registers that do not succeeded the
>   match.
> * handle_cpreg_kvm2tcg_migration(): try to solve the mismatch of
>   cp registers coming from KVM; without this additional step the
>   migration would fail even if it's feasible.
>
> Signed-off-by: Alvise Rigo <address@hidden>
> ---
>  target-arm/cpu.h     |  43 +++++++++++++
>  target-arm/helper.c  | 167 
> +++++++++++++++++++++++++++++++++++++++++++++++++--
>  target-arm/machine.c |  46 ++++++++++----
>  3 files changed, 238 insertions(+), 18 deletions(-)
>
> diff --git a/target-arm/cpu.h b/target-arm/cpu.h
> index 3c8a2db..a97246d 100644
> --- a/target-arm/cpu.h
> +++ b/target-arm/cpu.h
> @@ -184,6 +184,8 @@ typedef struct CPUARMState {
>                          MPU write buffer control.  */
>          uint32_t c5_insn; /* Fault status registers.  */
>          uint32_t c5_data;
> +        uint32_t c5_adfsr;
> +        uint32_t c5_aifsr;
>          uint32_t c6_region[8]; /* MPU base/size registers.  */
>          uint32_t c6_insn; /* Fault address registers.  */
>          uint32_t c6_data;
> @@ -197,6 +199,7 @@ typedef struct CPUARMState {
>          uint32_t c9_pmxevtyper; /* perf monitor event type */
>          uint32_t c9_pmuserenr; /* perf monitor user enable */
>          uint32_t c9_pminten; /* perf monitor interrupt enables */
> +        uint32_t c9_l2ctlr; /* L2 Control Register */
>          uint32_t c12_vbar; /* vector base address register */
>          uint32_t c13_fcse; /* FCSE PID.  */
>          uint32_t c13_context; /* Context ID.  */
> @@ -867,6 +870,15 @@ struct ARMCPRegInfo {
>      uint8_t opc0;
>      uint8_t opc1;
>      uint8_t opc2;
> +    /* When migrating this flag tells if the register's value has already
> +     * been copied. This is used in some unlikely cases where KVM migrates
> +     * a register that in TCG is generated by a wildcarded or
> +     * ARM_CP_STATE_BOTH parent (hence a not migratable register);
> +     * in those cases, we will set the field "parent" to point to the
> +     * generating register. Most of the time this field can stay false.
> +     * */
> +    bool skip_cpreglist;

This reads to me like it's papering over a problem rather
than fixing it.

thanks
-- PMM