linux-kernel - Re: [RFC PATCH 10/13] softmmu/physmem: Add private memory address space

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Message-ID: <0ea887e9-1fd4-1962-cbaa-92b648b28b53@amsat.org>
Date:   Tue, 18 Jan 2022 10:41:16 +0100
From:   Philippe Mathieu-Daudé <f4bug@...at.org>
To:     Chao Peng <chao.p.peng@...ux.intel.com>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        linux-fsdevel@...r.kernel.org, qemu-devel@...gnu.org
Cc:     Wanpeng Li <wanpengli@...cent.com>, jun.nakajima@...el.com,
        david@...hat.com, "J . Bruce Fields" <bfields@...ldses.org>,
        dave.hansen@...el.com, "H . Peter Anvin" <hpa@...or.com>,
        ak@...ux.intel.com, Jonathan Corbet <corbet@....net>,
        Joerg Roedel <joro@...tes.org>, x86@...nel.org,
        Hugh Dickins <hughd@...gle.com>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        luto@...nel.org, Thomas Gleixner <tglx@...utronix.de>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Jim Mattson <jmattson@...gle.com>,
        Sean Christopherson <seanjc@...gle.com>, susie.li@...el.com,
        Jeff Layton <jlayton@...nel.org>, john.ji@...el.com,
        Yu Zhang <yu.c.zhang@...ux.intel.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>
Subject: Re: [RFC PATCH 10/13] softmmu/physmem: Add private memory address
 space

Hi,

On 11/11/21 15:13, Chao Peng wrote:
> Signed-off-by: Chao Peng <chao.p.peng@...ux.intel.com>
> ---
>  include/exec/address-spaces.h |  2 ++
>  softmmu/physmem.c             | 13 +++++++++++++
>  2 files changed, 15 insertions(+)
> 
> diff --git a/include/exec/address-spaces.h b/include/exec/address-spaces.h
> index db8bfa9a92..b3f45001c0 100644
> --- a/include/exec/address-spaces.h
> +++ b/include/exec/address-spaces.h
> @@ -27,6 +27,7 @@
>   * until a proper bus interface is available.
>   */
>  MemoryRegion *get_system_memory(void);
> +MemoryRegion *get_system_private_memory(void);
>  
>  /* Get the root I/O port region.  This interface should only be used
>   * temporarily until a proper bus interface is available.
> @@ -34,6 +35,7 @@ MemoryRegion *get_system_memory(void);
>  MemoryRegion *get_system_io(void);
>  
>  extern AddressSpace address_space_memory;
> +extern AddressSpace address_space_private_memory;
>  extern AddressSpace address_space_io;
>  
>  #endif
> diff --git a/softmmu/physmem.c b/softmmu/physmem.c
> index f4d6eeaa17..a2d339fd88 100644
> --- a/softmmu/physmem.c
> +++ b/softmmu/physmem.c
> @@ -85,10 +85,13 @@
>  RAMList ram_list = { .blocks = QLIST_HEAD_INITIALIZER(ram_list.blocks) };
>  
>  static MemoryRegion *system_memory;
> +static MemoryRegion *system_private_memory;
>  static MemoryRegion *system_io;
>  
>  AddressSpace address_space_io;
>  AddressSpace address_space_memory;
> +AddressSpace address_space_private_memory;
> +
>  
>  static MemoryRegion io_mem_unassigned;
>  
> @@ -2669,6 +2672,11 @@ static void memory_map_init(void)
>      memory_region_init(system_memory, NULL, "system", UINT64_MAX);
>      address_space_init(&address_space_memory, system_memory, "memory");
>  
> +    system_private_memory = g_malloc(sizeof(*system_private_memory));
> +
> +    memory_region_init(system_private_memory, NULL, "system-private", UINT64_MAX);
> +    address_space_init(&address_space_private_memory, system_private_memory, "private-memory");

Since the description is quite scarce, I don't understand why we need to
add this KVM specific "system-private" MR/AS to all machines on all
architectures.

>      system_io = g_malloc(sizeof(*system_io));
>      memory_region_init_io(system_io, NULL, &unassigned_io_ops, NULL, "io",
>                            65536);

(We already want to get ride of the "io" MR/AS which is specific to
x86 or machines).

> @@ -2680,6 +2688,11 @@ MemoryRegion *get_system_memory(void)
>      return system_memory;
>  }
>  
> +MemoryRegion *get_system_private_memory(void)
> +{
> +    return system_private_memory;
> +}
> +
>  MemoryRegion *get_system_io(void)
>  {
>      return system_io;