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Peter Anvin" , Hugh Dickins , Jeff Layton , "J . Bruce Fields" , Andrew Morton , Shuah Khan , Mike Rapoport , Steven Price , "Maciej S . Szmigiero" , Vlastimil Babka , Vishal Annapurve , Yu Zhang , "Kirill A . Shutemov" , luto@kernel.org, jun.nakajima@intel.com, dave.hansen@intel.com, ak@linux.intel.com, david@redhat.com, aarcange@redhat.com, ddutile@redhat.com, dhildenb@redhat.com, Quentin Perret , tabba@google.com, Michael Roth , mhocko@suse.com, wei.w.wang@intel.com Subject: Re: [PATCH v10 3/9] KVM: Extend the memslot to support fd-based private memory Message-ID: <20221220074318.GC1724933@chaop.bj.intel.com> Reply-To: Chao Peng References: <20221202061347.1070246-1-chao.p.peng@linux.intel.com> <20221202061347.1070246-4-chao.p.peng@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 84605100003 X-Rspam-User: X-Stat-Signature: hocw33wh1e1qh3em1r7qimg8hgyt6wac X-HE-Tag: 1671522469-723856 X-HE-Meta: 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Mon, Dec 19, 2022 at 03:36:28PM +0100, Borislav Petkov wrote: > On Fri, Dec 02, 2022 at 02:13:41PM +0800, Chao Peng wrote: > > In memory encryption usage, guest memory may be encrypted with special > > key and can be accessed only by the guest itself. We call such memory > > private memory. It's valueless and sometimes can cause problem to allow > > valueless? > > I can't parse that. It's unnecessary and ... > > > userspace to access guest private memory. This new KVM memslot extension > > allows guest private memory being provided through a restrictedmem > > backed file descriptor(fd) and userspace is restricted to access the > > bookmarked memory in the fd. > > bookmarked? userspace is restricted to access the memory content in the fd. > > > This new extension, indicated by the new flag KVM_MEM_PRIVATE, adds two > > additional KVM memslot fields restricted_fd/restricted_offset to allow > > userspace to instruct KVM to provide guest memory through restricted_fd. > > 'guest_phys_addr' is mapped at the restricted_offset of restricted_fd > > and the size is 'memory_size'. > > > > The extended memslot can still have the userspace_addr(hva). When use, a > > "When un use, ..." When both userspace_addr and restricted_fd/offset were used, ... > > ... > > > diff --git a/arch/x86/kvm/Kconfig b/arch/x86/kvm/Kconfig > > index a8e379a3afee..690cb21010e7 100644 > > --- a/arch/x86/kvm/Kconfig > > +++ b/arch/x86/kvm/Kconfig > > @@ -50,6 +50,8 @@ config KVM > > select INTERVAL_TREE > > select HAVE_KVM_PM_NOTIFIER if PM > > select HAVE_KVM_MEMORY_ATTRIBUTES > > + select HAVE_KVM_RESTRICTED_MEM if X86_64 > > + select RESTRICTEDMEM if HAVE_KVM_RESTRICTED_MEM > > Those deps here look weird. > > RESTRICTEDMEM should be selected by TDX_GUEST as it can't live without > it. RESTRICTEDMEM is needed by TDX_HOST, not TDX_GUEST. > > Then you don't have to select HAVE_KVM_RESTRICTED_MEM simply because of > X86_64 - you need that functionality when the respective guest support > is enabled in KVM. Letting the actual feature(e.g. TDX or pKVM) select it or add dependency sounds a viable and clearer solution. Sean, let me know your opinion. > > Then, looking forward into your patchset, I'm not sure you even > need HAVE_KVM_RESTRICTED_MEM - you could make it all depend on > CONFIG_RESTRICTEDMEM. But that's KVM folks call - I'd always aim for > less Kconfig items because we have waay too many. The only reason to add another HAVE_KVM_RESTRICTED_MEM is some code only works for 64bit[*] and CONFIG_RESTRICTEDMEM is not sufficient to enforce that. [*] https://lore.kernel.org/all/YkJLFu98hZOvTSrL@google.com/ Thanks, Chao > > Thx. > > -- > Regards/Gruss, > Boris. > > https://people.kernel.org/tglx/notes-about-netiquette