Re: [PATCH v3 6/7] xen: introduce Kconfig ARCH_PAGING_MEMPOOL

[Oleksii Kurochko <oleksii.kurochko@gmail.com>]

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On 3/17/25 9:07 PM, Luca Fancellu wrote:
> From: Penny Zheng<Penny.Zheng@arm.com>
>
> ARM MPU system doesn't need to use paging memory pool, as MPU memory
> mapping table at most takes only one 4KB page, which is enough to
> manage the maximum 255 MPU memory regions, for all EL2 stage 1
> translation and EL1 stage 2 translation.
>
> Introduce ARCH_PAGING_MEMPOOL Kconfig common symbol, selected for Arm
> MMU systems, x86 and RISC-V.
>
> Wrap the code inside 'construct_domU' that deal with p2m paging
> allocation in a new function 'domain_p2m_set_allocation', protected
> by ARCH_PAGING_MEMPOOL, this is done in this way to prevent polluting
> the former function with #ifdefs and improve readability
>
> Introduce arch_{get,set}_paging_mempool_size stubs for architecture
> with !ARCH_PAGING_MEMPOOL.
>
> Remove 'struct paging_domain' from Arm 'struct arch_domain' when the
> field is not required.
>
> Signed-off-by: Penny Zheng<penny.zheng@arm.com>
> Signed-off-by: Wei Chen<wei.chen@arm.com>
> Signed-off-by: Luca Fancellu<luca.fancellu@arm.com>
> ---
> v3 changes:
>   - Introduced ARCH_PAGING_MEMPOOL instead of HAS_PAGING_MEMPOOL
> v2 changes:
>   - make Kconfig HAS_PAGING_MEMPOOL common
>   - protect also "xen,domain-p2m-mem-mb" reading with HAS_PAGING_MEMPOOL
>   - do not define p2m_teardown{_allocation} in this patch
>   - change commit message
> ---
>   xen/arch/arm/Kconfig              |  1 +
>   xen/arch/arm/dom0less-build.c     | 74 ++++++++++++++++++++-----------
>   xen/arch/arm/include/asm/domain.h |  2 +
>   xen/arch/riscv/Kconfig            |  1 +
>   xen/arch/x86/Kconfig              |  1 +
>   xen/common/Kconfig                |  3 ++
>   xen/include/xen/domain.h          | 17 +++++++
>   7 files changed, 73 insertions(+), 26 deletions(-)

For RISC-V:
  Reviewed-by: Oleksii Kurochko<oleksii.kurochko@gmail.com>

Thanks.

~ Oleksii

>
> diff --git a/xen/arch/arm/Kconfig b/xen/arch/arm/Kconfig
> index 5ac6ec0212d2..a4af0b85f158 100644
> --- a/xen/arch/arm/Kconfig
> +++ b/xen/arch/arm/Kconfig
> @@ -75,6 +75,7 @@ choice
>   
>   config MMU
>   	bool "MMU"
> +	select ARCH_PAGING_MEMPOOL
>   	select HAS_LLC_COLORING if !NUMA && ARM_64
>   	select HAS_PMAP
>   	select HAS_VMAP
> diff --git a/xen/arch/arm/dom0less-build.c b/xen/arch/arm/dom0less-build.c
> index 573b0d25ae41..6eef6ba91444 100644
> --- a/xen/arch/arm/dom0less-build.c
> +++ b/xen/arch/arm/dom0less-build.c
> @@ -673,21 +673,6 @@ static int __init prepare_dtb_domU(struct domain *d, struct kernel_info *kinfo)
>       return -EINVAL;
>   }
>   
> -static unsigned long __init domain_p2m_pages(unsigned long maxmem_kb,
> -                                             unsigned int smp_cpus)
> -{
> -    /*
> -     * Keep in sync with libxl__get_required_paging_memory().
> -     * 256 pages (1MB) per vcpu, plus 1 page per MiB of RAM for the P2M map,
> -     * plus 128 pages to cover extended regions.
> -     */
> -    unsigned long memkb = 4 * (256 * smp_cpus + (maxmem_kb / 1024) + 128);
> -
> -    BUILD_BUG_ON(PAGE_SIZE != SZ_4K);
> -
> -    return DIV_ROUND_UP(memkb, 1024) << (20 - PAGE_SHIFT);
> -}
> -
>   static int __init alloc_xenstore_evtchn(struct domain *d)
>   {
>       evtchn_alloc_unbound_t alloc;
> @@ -841,6 +826,53 @@ static void __init domain_vcpu_affinity(struct domain *d,
>       }
>   }
>   
> +#ifdef CONFIG_ARCH_PAGING_MEMPOOL
> +
> +static unsigned long __init domain_p2m_pages(unsigned long maxmem_kb,
> +                                             unsigned int smp_cpus)
> +{
> +    /*
> +     * Keep in sync with libxl__get_required_paging_memory().
> +     * 256 pages (1MB) per vcpu, plus 1 page per MiB of RAM for the P2M map,
> +     * plus 128 pages to cover extended regions.
> +     */
> +    unsigned long memkb = 4 * (256 * smp_cpus + (maxmem_kb / 1024) + 128);
> +
> +    BUILD_BUG_ON(PAGE_SIZE != SZ_4K);
> +
> +    return DIV_ROUND_UP(memkb, 1024) << (20 - PAGE_SHIFT);
> +}
> +
> +static int __init domain_p2m_set_allocation(struct domain *d, uint64_t mem,
> +                                            const struct dt_device_node *node)
> +{
> +    unsigned long p2m_pages;
> +    uint32_t p2m_mem_mb;
> +    int rc;
> +
> +    rc = dt_property_read_u32(node, "xen,domain-p2m-mem-mb", &p2m_mem_mb);
> +    /* If xen,domain-p2m-mem-mb is not specified, use the default value. */
> +    p2m_pages = rc ?
> +                p2m_mem_mb << (20 - PAGE_SHIFT) :
> +                domain_p2m_pages(mem, d->max_vcpus);
> +
> +    spin_lock(&d->arch.paging.lock);
> +    rc = p2m_set_allocation(d, p2m_pages, NULL);
> +    spin_unlock(&d->arch.paging.lock);
> +
> +    return rc;
> +}
> +
> +#else /* !CONFIG_ARCH_PAGING_MEMPOOL */
> +
> +static inline int domain_p2m_set_allocation(struct domain *d, uint64_t mem,
> +                                            const struct dt_device_node *node)
> +{
> +    return 0;
> +}
> +
> +#endif /* CONFIG_ARCH_PAGING_MEMPOOL */
> +
>   static int __init construct_domU(struct domain *d,
>                                    const struct dt_device_node *node)
>   {
> @@ -848,8 +880,6 @@ static int __init construct_domU(struct domain *d,
>       const char *dom0less_enhanced;
>       int rc;
>       u64 mem;
> -    u32 p2m_mem_mb;
> -    unsigned long p2m_pages;
>   
>       rc = dt_property_read_u64(node, "memory", &mem);
>       if ( !rc )
> @@ -859,15 +889,7 @@ static int __init construct_domU(struct domain *d,
>       }
>       kinfo.unassigned_mem = (paddr_t)mem * SZ_1K;
>   
> -    rc = dt_property_read_u32(node, "xen,domain-p2m-mem-mb", &p2m_mem_mb);
> -    /* If xen,domain-p2m-mem-mb is not specified, use the default value. */
> -    p2m_pages = rc ?
> -                p2m_mem_mb << (20 - PAGE_SHIFT) :
> -                domain_p2m_pages(mem, d->max_vcpus);
> -
> -    spin_lock(&d->arch.paging.lock);
> -    rc = p2m_set_allocation(d, p2m_pages, NULL);
> -    spin_unlock(&d->arch.paging.lock);
> +    rc = domain_p2m_set_allocation(d, mem, node);
>       if ( rc != 0 )
>           return rc;
>   
> diff --git a/xen/arch/arm/include/asm/domain.h b/xen/arch/arm/include/asm/domain.h
> index 50b6a4b00982..a3487ca71303 100644
> --- a/xen/arch/arm/include/asm/domain.h
> +++ b/xen/arch/arm/include/asm/domain.h
> @@ -75,7 +75,9 @@ struct arch_domain
>   
>       struct hvm_domain hvm;
>   
> +#ifdef CONFIG_ARCH_PAGING_MEMPOOL
>       struct paging_domain paging;
> +#endif
>   
>       struct vmmio vmmio;
>   
> diff --git a/xen/arch/riscv/Kconfig b/xen/arch/riscv/Kconfig
> index d882e0a0598d..1bd8ae16dc65 100644
> --- a/xen/arch/riscv/Kconfig
> +++ b/xen/arch/riscv/Kconfig
> @@ -1,5 +1,6 @@
>   config RISCV
>   	def_bool y
> +	select ARCH_PAGING_MEMPOOL
>   	select FUNCTION_ALIGNMENT_16B
>   	select GENERIC_BUG_FRAME
>   	select HAS_DEVICE_TREE
> diff --git a/xen/arch/x86/Kconfig b/xen/arch/x86/Kconfig
> index f08679959440..f6aa892661b4 100644
> --- a/xen/arch/x86/Kconfig
> +++ b/xen/arch/x86/Kconfig
> @@ -9,6 +9,7 @@ config X86
>   	select ACPI_NUMA
>   	select ALTERNATIVE_CALL
>   	select ARCH_MAP_DOMAIN_PAGE
> +	select ARCH_PAGING_MEMPOOL
>   	select ARCH_SUPPORTS_INT128
>   	imply CORE_PARKING
>   	select FUNCTION_ALIGNMENT_16B
> diff --git a/xen/common/Kconfig b/xen/common/Kconfig
> index a6aa2c5c1456..218357d593b7 100644
> --- a/xen/common/Kconfig
> +++ b/xen/common/Kconfig
> @@ -44,6 +44,9 @@ config ALTERNATIVE_CALL
>   config ARCH_MAP_DOMAIN_PAGE
>   	bool
>   
> +config ARCH_PAGING_MEMPOOL
> +	bool
> +
>   config GENERIC_BUG_FRAME
>   	bool
>   
> diff --git a/xen/include/xen/domain.h b/xen/include/xen/domain.h
> index 83069de50118..a34daa7d10ab 100644
> --- a/xen/include/xen/domain.h
> +++ b/xen/include/xen/domain.h
> @@ -2,6 +2,7 @@
>   #ifndef __XEN_DOMAIN_H__
>   #define __XEN_DOMAIN_H__
>   
> +#include <xen/errno.h>
>   #include <xen/numa.h>
>   #include <xen/types.h>
>   
> @@ -114,9 +115,25 @@ void arch_get_info_guest(struct vcpu *v, vcpu_guest_context_u c);
>   int arch_initialise_vcpu(struct vcpu *v, XEN_GUEST_HANDLE_PARAM(void) arg);
>   int default_initialise_vcpu(struct vcpu *v, XEN_GUEST_HANDLE_PARAM(void) arg);
>   
> +#ifdef CONFIG_ARCH_PAGING_MEMPOOL
> +
>   int arch_get_paging_mempool_size(struct domain *d, uint64_t *size /* bytes */);
>   int arch_set_paging_mempool_size(struct domain *d, uint64_t size /* bytes */);
>   
> +#else /* !CONFIG_ARCH_PAGING_MEMPOOL */
> +
> +static inline int arch_get_paging_mempool_size(struct domain *d, uint64_t *size)
> +{
> +    return -EOPNOTSUPP;
> +}
> +
> +static inline int arch_set_paging_mempool_size(struct domain *d, uint64_t size)
> +{
> +    return -EOPNOTSUPP;
> +}
> +
> +#endif /* CONFIG_ARCH_PAGING_MEMPOOL */
> +
>   bool update_runstate_area(struct vcpu *v);
>   
>   int domain_relinquish_resources(struct domain *d);

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