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[134.134.136.126]) by mx.google.com with ESMTPS id w18si5108pjn.74.2019.06.17.11.07.46 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 17 Jun 2019 11:07:46 -0700 (PDT) Received-SPF: pass (google.com: domain of dave.hansen@intel.com designates 134.134.136.126 as permitted sender) client-ip=134.134.136.126; Authentication-Results: mx.google.com; spf=pass (google.com: domain of dave.hansen@intel.com designates 134.134.136.126 as permitted sender) smtp.mailfrom=dave.hansen@intel.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=intel.com X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga002.jf.intel.com ([10.7.209.21]) by orsmga106.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 17 Jun 2019 11:07:45 -0700 X-ExtLoop1: 1 Received: from ray.jf.intel.com (HELO [10.7.201.126]) ([10.7.201.126]) by orsmga002.jf.intel.com with ESMTP; 17 Jun 2019 11:07:45 -0700 Subject: Re: [RFC 00/10] Process-local memory allocations for hiding KVM secrets To: Nadav Amit , Andy Lutomirski Cc: Alexander Graf , Thomas Gleixner , Marius Hillenbrand , kvm list , LKML , Kernel Hardening , Linux-MM , Alexander Graf , David Woodhouse , the arch/x86 maintainers , Peter Zijlstra References: <20190612170834.14855-1-mhillenb@amazon.de> <58788f05-04c3-e71c-12c3-0123be55012c@amazon.com> <63b1b249-6bc7-ffd9-99db-d36dd3f1a962@intel.com> <698ca264-123d-46ae-c165-ed62ea149896@intel.com> <5AA8BF10-8987-4FCB-870C-667A5228D97B@gmail.com> From: Dave Hansen Openpgp: preference=signencrypt Autocrypt: addr=dave.hansen@intel.com; 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Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.0 MIME-Version: 1.0 In-Reply-To: <5AA8BF10-8987-4FCB-870C-667A5228D97B@gmail.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit 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 6/17/19 9:53 AM, Nadav Amit wrote: >>> For anyone following along at home, I'm going to go off into crazy >>> per-cpu-pgds speculation mode now... Feel free to stop reading now. :) >>> >>> But, I was thinking we could get away with not doing this on _every_ >>> context switch at least. For instance, couldn't 'struct tlb_context' >>> have PGD pointer (or two with PTI) in addition to the TLB info? That >>> way we only do the copying when we change the context. Or does that tie >>> the implementation up too much with PCIDs? >> Hmm, that seems entirely reasonable. I think the nasty bit would be >> figuring out all the interactions with PV TLB flushing. PV TLB >> flushes already don't play so well with PCID tracking, and this will >> make it worse. We probably need to rewrite all that code regardless. > How is PCID (as you implemented) related to TLB flushing of kernel (not > user) PTEs? These kernel PTEs would be global, so they would be invalidated > from all the address-spaces using INVLPG, I presume. No? The idea is that you have a per-cpu address space. Certain kernel virtual addresses would map to different physical address based on where you are running. Each of the physical addresses would be "owned" by a single CPU and would, by convention, never use a PGD that mapped an address unless that CPU that "owned" it. In that case, you never really invalidate those addresses.