From: Isaku Yamahata <isaku.yamahata@linux.intel.com>
To: "Huang, Kai" <kai.huang@intel.com>
Cc: "kvm@vger.kernel.org" <kvm@vger.kernel.org>,
"Yamahata, Isaku" <isaku.yamahata@intel.com>,
"federico.parola@polito.it" <federico.parola@polito.it>,
"pbonzini@redhat.com" <pbonzini@redhat.com>,
"dmatlack@google.com" <dmatlack@google.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"isaku.yamahata@gmail.com" <isaku.yamahata@gmail.com>,
"michael.roth@amd.com" <michael.roth@amd.com>,
"seanjc@google.com" <seanjc@google.com>,
isaku.yamahata@linux.intel.com
Subject: Re: [RFC PATCH 1/8] KVM: Document KVM_MAP_MEMORY ioctl
Date: Thu, 7 Mar 2024 12:33:40 -0800 [thread overview]
Message-ID: <20240307203340.GI368614@ls.amr.corp.intel.com> (raw)
In-Reply-To: <9f8d8e3b707de3cd879e992a30d646475c608678.camel@intel.com>
On Thu, Mar 07, 2024 at 12:30:04PM +0000,
"Huang, Kai" <kai.huang@intel.com> wrote:
> On Fri, 2024-03-01 at 09:28 -0800, isaku.yamahata@intel.com wrote:
> > From: Isaku Yamahata <isaku.yamahata@intel.com>
> >
> > Adds documentation of KVM_MAP_MEMORY ioctl.
> >
> > It pre-populates guest memory. And potentially do initialized memory
> > contents with encryption and measurement depending on underlying
> > technology.
> >
> > Suggested-by: Sean Christopherson <seanjc@google.com>
> > Signed-off-by: Isaku Yamahata <isaku.yamahata@intel.com>
> > ---
> > Documentation/virt/kvm/api.rst | 36 ++++++++++++++++++++++++++++++++++
> > 1 file changed, 36 insertions(+)
> >
> > diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
> > index 0b5a33ee71ee..33d2b63f7dbf 100644
> > --- a/Documentation/virt/kvm/api.rst
> > +++ b/Documentation/virt/kvm/api.rst
> > @@ -6352,6 +6352,42 @@ a single guest_memfd file, but the bound ranges must not overlap).
> >
> > See KVM_SET_USER_MEMORY_REGION2 for additional details.
> >
> > +4.143 KVM_MAP_MEMORY
> > +------------------------
> > +
> > +:Capability: KVM_CAP_MAP_MEMORY
> > +:Architectures: none
> > +:Type: vcpu ioctl
>
> I think "vcpu ioctl" means theoretically it can be called on multiple vcpus.
>
> What happens in that case?
Each vcpu can handle the ioctl simaltaneously. If we assume tdp_mmu, each vcpu
calls the kvm fault handler simultaneously with read spinlock.
If gfn ranges overlap, vcpu will get 0 (success) or EAGAIN.
> > +:Parameters: struct kvm_memory_mapping(in/out)
> > +:Returns: 0 on success, <0 on error
> > +
> > +KVM_MAP_MEMORY populates guest memory without running vcpu.
> > +
> > +::
> > +
> > + struct kvm_memory_mapping {
> > + __u64 base_gfn;
> > + __u64 nr_pages;
> > + __u64 flags;
> > + __u64 source;
> > + };
> > +
> > + /* For kvm_memory_mapping:: flags */
> > + #define KVM_MEMORY_MAPPING_FLAG_WRITE _BITULL(0)
> > + #define KVM_MEMORY_MAPPING_FLAG_EXEC _BITULL(1)
> > + #define KVM_MEMORY_MAPPING_FLAG_USER _BITULL(2)
>
> I am not sure what's the good of having "FLAG_USER"?
>
> This ioctl is called from userspace, thus I think we can just treat this always
> as user-fault?
The point is how to emulate kvm page fault as if vcpu caused the kvm page
fault. Not we call the ioctl as user context.
--
Isaku Yamahata <isaku.yamahata@linux.intel.com>
next prev parent reply other threads:[~2024-03-07 20:33 UTC|newest]
Thread overview: 54+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-03-01 17:28 [RFC PATCH 0/8] KVM: Prepopulate guest memory API isaku.yamahata
2024-03-01 17:28 ` [RFC PATCH 1/8] KVM: Document KVM_MAP_MEMORY ioctl isaku.yamahata
2024-03-07 0:43 ` David Matlack
2024-03-07 1:29 ` Isaku Yamahata
2024-03-07 12:30 ` Huang, Kai
2024-03-07 20:33 ` Isaku Yamahata [this message]
2024-03-08 0:20 ` Huang, Kai
2024-03-08 0:56 ` David Matlack
2024-03-08 1:28 ` Sean Christopherson
2024-03-08 2:19 ` Isaku Yamahata
2024-03-10 23:12 ` Michael Roth
2024-03-11 1:05 ` Huang, Kai
2024-03-11 1:08 ` Huang, Kai
2024-03-12 1:34 ` Isaku Yamahata
2024-03-01 17:28 ` [RFC PATCH 2/8] KVM: Add KVM_MAP_MEMORY vcpu ioctl to pre-populate guest memory isaku.yamahata
2024-03-07 0:49 ` David Matlack
2024-03-07 2:52 ` Isaku Yamahata
2024-03-07 12:45 ` Huang, Kai
2024-03-07 20:41 ` Isaku Yamahata
2024-03-11 17:23 ` Sean Christopherson
2024-03-11 22:19 ` Isaku Yamahata
2024-03-01 17:28 ` [RFC PATCH 3/8] KVM: x86/mmu: Introduce initialier macro for struct kvm_page_fault isaku.yamahata
2024-03-11 17:24 ` Sean Christopherson
2024-03-11 22:56 ` Isaku Yamahata
2024-03-01 17:28 ` [RFC PATCH 4/8] KVM: x86/mmu: Factor out kvm_mmu_do_page_fault() isaku.yamahata
2024-03-01 17:28 ` [RFC PATCH 5/8] KVM: x86/mmu: Introduce kvm_mmu_map_page() for prepopulating guest memory isaku.yamahata
2024-03-07 0:38 ` David Matlack
2024-03-19 15:53 ` Isaku Yamahata
2024-03-11 17:29 ` Sean Christopherson
2024-03-11 22:57 ` Isaku Yamahata
2024-03-01 17:28 ` [RFC PATCH 6/8] KVM: x86: Implement kvm_arch_{, pre_}vcpu_map_memory() isaku.yamahata
2024-03-07 0:30 ` David Matlack
2024-03-07 0:36 ` David Matlack
2024-03-07 1:51 ` Isaku Yamahata
2024-03-19 16:26 ` Isaku Yamahata
2024-04-03 23:15 ` Sean Christopherson
2024-03-07 1:34 ` Isaku Yamahata
2024-03-11 23:26 ` Sean Christopherson
2024-03-12 12:38 ` Huang, Kai
2024-03-12 14:20 ` Sean Christopherson
2024-03-12 21:41 ` Huang, Kai
2024-03-12 21:46 ` Huang, Kai
2024-03-12 23:03 ` Sean Christopherson
2024-03-01 17:28 ` [RFC PATCH 7/8] KVM: x86: Add hooks in kvm_arch_vcpu_map_memory() isaku.yamahata
2024-03-01 17:28 ` [RFC PATCH 8/8] KVM: selftests: x86: Add test for KVM_MAP_MEMORY isaku.yamahata
2024-03-07 0:53 ` [RFC PATCH 0/8] KVM: Prepopulate guest memory API David Matlack
2024-03-07 2:09 ` Isaku Yamahata
2024-03-19 16:33 ` Isaku Yamahata
2024-04-03 18:30 ` Sean Christopherson
2024-04-03 22:00 ` Isaku Yamahata
2024-04-03 22:42 ` Sean Christopherson
2024-03-11 3:20 ` Michael Roth
2024-03-11 23:44 ` Sean Christopherson
2024-03-12 1:32 ` Isaku Yamahata
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