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Date: Fri, 16 Sep 2022 17:53:42 +0800
From: Chao Peng <chao.p.peng@...ux.intel.com>
To: Bagas Sanjaya <bagasdotme@...il.com>
Cc: kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-mm@...ck.org, linux-fsdevel@...r.kernel.org,
linux-api@...r.kernel.org, linux-doc@...r.kernel.org,
qemu-devel@...gnu.org, Paolo Bonzini <pbonzini@...hat.com>,
Jonathan Corbet <corbet@....net>,
Sean Christopherson <seanjc@...gle.com>,
Vitaly Kuznetsov <vkuznets@...hat.com>,
Wanpeng Li <wanpengli@...cent.com>,
Jim Mattson <jmattson@...gle.com>,
Joerg Roedel <joro@...tes.org>,
Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
x86@...nel.org, "H . Peter Anvin" <hpa@...or.com>,
Hugh Dickins <hughd@...gle.com>,
Jeff Layton <jlayton@...nel.org>,
"J . Bruce Fields" <bfields@...ldses.org>,
Andrew Morton <akpm@...ux-foundation.org>,
Shuah Khan <shuah@...nel.org>, Mike Rapoport <rppt@...nel.org>,
Steven Price <steven.price@....com>,
"Maciej S . Szmigiero" <mail@...iej.szmigiero.name>,
Vlastimil Babka <vbabka@...e.cz>,
Vishal Annapurve <vannapurve@...gle.com>,
Yu Zhang <yu.c.zhang@...ux.intel.com>,
"Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
luto@...nel.org, jun.nakajima@...el.com, dave.hansen@...el.com,
ak@...ux.intel.com, david@...hat.com, aarcange@...hat.com,
ddutile@...hat.com, dhildenb@...hat.com,
Quentin Perret <qperret@...gle.com>,
Michael Roth <michael.roth@....com>, mhocko@...e.com,
Muchun Song <songmuchun@...edance.com>, wei.w.wang@...el.com
Subject: Re: [PATCH v8 2/8] KVM: Extend the memslot to support fd-based
private memory
On Fri, Sep 16, 2022 at 04:14:29PM +0700, Bagas Sanjaya wrote:
> 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
> >
> > ::
> > @@ -1332,9 +1332,18 @@ yet and must be cleared on entry.
> > __u64 userspace_addr; /* start of the userspace allocated memory */
> > };
> >
> > + 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)
> >
> > 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.
> >
> > -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 how to
> > -use it. The latter 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 be
> > -posted to userspace as KVM_EXIT_MMIO exits.
> > +kvm_userspace_memory_region_ext includes all the kvm_userspace_memory_region
> > +fields. It also includes additional fields for some specific features. See
> > +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 writes to
> > + memory within the slot. See KVM_GET_DIRTY_LOG ioctl to know how to use 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 be 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 backed by
> > + a file descirptor(fd) and the content of the private memory is invisible to
> > + userspace. In this case, userspace should use private_fd/private_offset in
> > + kvm_userspace_memory_region_ext to instruct KVM to provide private memory to
> > + guest. Userspace should guarantee not to map the same pfn indicated by
> > + private_fd/private_offset to different gfns with multiple memslots. Failed to
> > + do this may result undefined behavior.
> >
>
> For the lists above,
> s/can be set/
It all looks good, thanks!
>
> Thanks.
>
> --
> An old man doll... just what I always wanted! - Clara
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