Re: [PATCH v2 11/35] xen/domain: enable max_init_domid for all architectures

["Roger Pau Monné" <roger.pau@citrix.com>]

On Thu, Dec 05, 2024 at 08:41:41PM -0800, Denis Mukhin via B4 Relay wrote:
> From: Denis Mukhin <dmukhin@ford.com>
> 
> Move max_init_domid to a public API and enable for all architectures.
> That is pre-requisite change for console focus switch logic cleanup.
> 
> max_init_domid is updated in domain_create().
> 
> Signed-off-by: Denis Mukhin <dmukhin@ford.com>
> ---
>  xen/arch/arm/include/asm/setup.h   | 2 --
>  xen/arch/arm/setup.c               | 2 --
>  xen/arch/ppc/include/asm/setup.h   | 2 --
>  xen/arch/riscv/include/asm/setup.h | 2 --
>  xen/arch/x86/include/asm/setup.h   | 2 --
>  xen/common/domain.c                | 9 +++++++++
>  xen/include/xen/domain.h           | 2 ++
>  7 files changed, 11 insertions(+), 10 deletions(-)
> 
> diff --git a/xen/arch/arm/include/asm/setup.h b/xen/arch/arm/include/asm/setup.h
> index 64c227d171fc7b92e5b62d9fd42e5662871bd12b..d4e1670cd69cdd4475b2a5eb316d2c0601090ed7 100644
> --- a/xen/arch/arm/include/asm/setup.h
> +++ b/xen/arch/arm/include/asm/setup.h
> @@ -19,8 +19,6 @@ struct map_range_data
>      struct rangeset *irq_ranges;
>  };
>  
> -extern domid_t max_init_domid;
> -
>  void copy_from_paddr(void *dst, paddr_t paddr, unsigned long len);
>  
>  size_t estimate_efi_size(unsigned int mem_nr_banks);
> diff --git a/xen/arch/arm/setup.c b/xen/arch/arm/setup.c
> index 2e27af4560a504bf57daef572d4a768bd886145b..cb218fe3eb36f2cdda47cfa092fa99ee1ca4a14c 100644
> --- a/xen/arch/arm/setup.c
> +++ b/xen/arch/arm/setup.c
> @@ -58,8 +58,6 @@ struct cpuinfo_arm __read_mostly system_cpuinfo;
>  bool __read_mostly acpi_disabled;
>  #endif
>  
> -domid_t __read_mostly max_init_domid;
> -
>  static __used void init_done(void)
>  {
>      int rc;
> diff --git a/xen/arch/ppc/include/asm/setup.h b/xen/arch/ppc/include/asm/setup.h
> index e4f64879b68ca5aac24bd9544255143e6ef693f3..956fa6985adb23375bd41d3e5d34d9d5f0712bd5 100644
> --- a/xen/arch/ppc/include/asm/setup.h
> +++ b/xen/arch/ppc/include/asm/setup.h
> @@ -1,6 +1,4 @@
>  #ifndef __ASM_PPC_SETUP_H__
>  #define __ASM_PPC_SETUP_H__
>  
> -#define max_init_domid (0)
> -
>  #endif /* __ASM_PPC_SETUP_H__ */
> diff --git a/xen/arch/riscv/include/asm/setup.h b/xen/arch/riscv/include/asm/setup.h
> index 844a2f0ef1d762b3a9bc90b61a336a23f1693cc9..978cad71d3df484e80ba19acc0e37b9278e941f0 100644
> --- a/xen/arch/riscv/include/asm/setup.h
> +++ b/xen/arch/riscv/include/asm/setup.h
> @@ -3,8 +3,6 @@
>  #ifndef ASM__RISCV__SETUP_H
>  #define ASM__RISCV__SETUP_H
>  
> -#define max_init_domid (0)
> -
>  void setup_mm(void);
>  
>  #endif /* ASM__RISCV__SETUP_H */
> diff --git a/xen/arch/x86/include/asm/setup.h b/xen/arch/x86/include/asm/setup.h
> index 5c2391a8684b66efdf4b092409ed33935db6b40c..296348655b9d146c73acc305cc9edd5fd46f7d47 100644
> --- a/xen/arch/x86/include/asm/setup.h
> +++ b/xen/arch/x86/include/asm/setup.h
> @@ -69,6 +69,4 @@ extern bool opt_dom0_verbose;
>  extern bool opt_dom0_cpuid_faulting;
>  extern bool opt_dom0_msr_relaxed;
>  
> -#define max_init_domid (0)
> -
>  #endif
> diff --git a/xen/common/domain.c b/xen/common/domain.c
> index 2f67aa06ed50e69c27cedc8d7f6eb0b469fe81cd..9e57dd4122a726e2fb42efe9c029e775202be0e6 100644
> --- a/xen/common/domain.c
> +++ b/xen/common/domain.c
> @@ -65,6 +65,9 @@ DEFINE_RCU_READ_LOCK(domlist_read_lock);
>  static struct domain *domain_hash[DOMAIN_HASH_SIZE];
>  struct domain *domain_list;
>  
> +/* Last known non-system domain ID. */
> +domid_t __read_mostly max_init_domid;

The comment (and implementation below) seems to differ from what Arm
dom0less code currently uses the variable for.

> +
>  /*
>   * Insert a domain into the domlist/hash.  This allows the domain to be looked
>   * up by domid, and therefore to be the subject of hypercalls/etc.
> @@ -815,6 +818,12 @@ struct domain *domain_create(domid_t domid,
>  
>      memcpy(d->handle, config->handle, sizeof(d->handle));
>  
> +    /*
> +     * Housekeeping for physical console forwarding to the domain.
> +     */
> +    if ( !is_system_domain(d) && max_init_domid < domid )
> +        max_init_domid = domid;

Don't you need to adjust the ARM dom0-less logic that deal with
increasing max_init_domid in create_domUs().

Also max_init_domid likely only wants to be updated for domains
created before the control domain is started, and hence could be
__ro_after_init instead of __read_mostly?

Thanks, Roger.