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Date:   Fri, 16 Sep 2022 16:14:29 +0700
From:   Bagas Sanjaya <bagasdotme@gmail.com>
To:     Chao Peng <chao.p.peng@linux.intel.com>
Cc:     kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-mm@kvack.org, linux-fsdevel@vger.kernel.org,
        linux-api@vger.kernel.org, linux-doc@vger.kernel.org,
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        Jonathan Corbet <corbet@lwn.net>,
        Sean Christopherson <seanjc@google.com>,
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        Wanpeng Li <wanpengli@tencent.com>,
        Jim Mattson <jmattson@google.com>,
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        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        x86@kernel.org, "H . Peter Anvin" <hpa@zytor.com>,
        Hugh Dickins <hughd@google.com>,
        Jeff Layton <jlayton@kernel.org>,
        "J . Bruce Fields" <bfields@fieldses.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Shuah Khan <shuah@kernel.org>, Mike Rapoport <rppt@kernel.org>,
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        "Maciej S . Szmigiero" <mail@maciej.szmigiero.name>,
        Vlastimil Babka <vbabka@suse.cz>,
        Vishal Annapurve <vannapurve@google.com>,
        Yu Zhang <yu.c.zhang@linux.intel.com>,
        "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>,
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        Quentin Perret <qperret@google.com>,
        Michael Roth <michael.roth@amd.com>, mhocko@suse.com,
        Muchun Song <songmuchun@bytedance.com>, wei.w.wang@intel.com
Subject: Re: [PATCH v8 2/8] KVM: Extend the memslot to support fd-based
 private memory
Message-ID: <YyQ+dQT9/V5e62/u@debian.me>
References: <20220915142913.2213336-1-chao.p.peng@linux.intel.com>
 <20220915142913.2213336-3-chao.p.peng@linux.intel.com>
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On Thu, Sep 15, 2022 at 10:29:07PM +0800, Chao Peng wrote:
> diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.=
rst
> index abd7c32126ce..c1fac1e9f820 100644
> --- a/Documentation/virt/kvm/api.rst
> +++ b/Documentation/virt/kvm/api.rst
> @@ -1319,7 +1319,7 @@ yet and must be cleared on entry.
>  :Capability: KVM_CAP_USER_MEMORY
>  :Architectures: all
>  :Type: vm ioctl
> -:Parameters: struct kvm_userspace_memory_region (in)
> +:Parameters: struct kvm_userspace_memory_region(_ext) (in)
>  :Returns: 0 on success, -1 on error
> =20
>  ::
> @@ -1332,9 +1332,18 @@ yet and must be cleared on entry.
>  	__u64 userspace_addr; /* start of the userspace allocated memory */
>    };
> =20
> +  struct kvm_userspace_memory_region_ext {
> +	struct kvm_userspace_memory_region region;
> +	__u64 private_offset;
> +	__u32 private_fd;
> +	__u32 pad1;
> +	__u64 pad2[14];
> +  };
> +
>    /* for kvm_memory_region::flags */
>    #define KVM_MEM_LOG_DIRTY_PAGES	(1UL << 0)
>    #define KVM_MEM_READONLY	(1UL << 1)
> +  #define KVM_MEM_PRIVATE		(1UL << 2)
> =20
>  This ioctl allows the user to create, modify or delete a guest physical
>  memory slot.  Bits 0-15 of "slot" specify the slot id and this value
> @@ -1365,12 +1374,27 @@ It is recommended that the lower 21 bits of guest=
_phys_addr and userspace_addr
>  be identical.  This allows large pages in the guest to be backed by large
>  pages in the host.
> =20
> -The flags field supports two flags: KVM_MEM_LOG_DIRTY_PAGES and
> -KVM_MEM_READONLY.  The former can be set to instruct KVM to keep track of
> -writes to memory within the slot.  See KVM_GET_DIRTY_LOG ioctl to know h=
ow to
> -use it.  The latter can be set, if KVM_CAP_READONLY_MEM capability allow=
s it,
> -to make a new slot read-only.  In this case, writes to this memory will =
be
> -posted to userspace as KVM_EXIT_MMIO exits.
> +kvm_userspace_memory_region_ext includes all the kvm_userspace_memory_re=
gion
> +fields. It also includes additional fields for some specific features. S=
ee
> +below description of flags field for more information. It's recommended =
to use
> +kvm_userspace_memory_region_ext in new userspace code.

Better say "kvm_userspace_memory_region_ext includes all fields of
kvm_userspace_memory_region struct, while also adds additional fields ..."

> +
> +The flags field supports below flags:

s/below/following/

> +
> +- KVM_MEM_LOG_DIRTY_PAGES can be set to instruct KVM to keep track of wr=
ites to
> +  memory within the slot.  See KVM_GET_DIRTY_LOG ioctl to know how to us=
e it.
> +

Better say "... For more details, see KVM_GET_DIRTY_LOG."

> +- KVM_MEM_READONLY can be set, if KVM_CAP_READONLY_MEM capability allows=
 it, to
> +  make a new slot read-only.  In this case, writes to this memory will b=
e posted
> +  to userspace as KVM_EXIT_MMIO exits.
> +

Better say "if KVM_CAP_READONLY_MEM allows, KVM_MEM_READONLY makes a new
slot read-only ..."

> +- KVM_MEM_PRIVATE can be set to indicate a new slot has private memory b=
acked by
> +  a file descirptor(fd) and the content of the private memory is invisib=
le to
> +  userspace. In this case, userspace should use private_fd/private_offse=
t in
> +  kvm_userspace_memory_region_ext to instruct KVM to provide private mem=
ory to
> +  guest. Userspace should guarantee not to map the same pfn indicated by
> +  private_fd/private_offset to different gfns with multiple memslots. Fa=
iled to
> +  do this may result undefined behavior.
> =20

For the lists above,
s/can be set/

Thanks.=20

--=20
An old man doll... just what I always wanted! - Clara

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