Messages in this thread | | | From | Andy Lutomirski <> | Date | Tue, 20 Mar 2018 15:05:26 +0000 | Subject | Re: [PATCH 00/15] x86: Enable FSGSBASE instructions |
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On Mon, Mar 19, 2018 at 5:49 PM, Chang S. Bae <chang.seok.bae@intel.com> wrote: > FSGSBASE is 64-bit instruction set to allow read/write > FS/GS base from any privilege. As introduced from > Ivybridge, enabling effort has been revolving quite long > [2,3,4] for various reasons. After extended discussions [1], > this patchset is proposed to introduce new ABIs of > customizing FS/GS base (separate from its selector). > > FSGSBASE-enabled VM can be located on hosts with > either HW virtualization or SW emulation. KVM advertises > FSGSBASE when physical CPU has and emulation is > supported in QEMU/TCG [5]. In a pool of mixed systems, VMM > may disable FSGSBASE for seamless VM migrations [6]. > > A couple of major benefits are expected. Kernel will have > performance improvement in context switch by skipping MSR > write for GS base. User-level programs (such as JAVA-based) > benefit from avoiding system calls to edit FS/GS base.
Can you describe what changed since the last submission? It looks like a lot has changed and this series is much more complicated and much more fragile than it used to be. Why?
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