[PATCH v2 0/7] KVM TSS cleanups and speedups

From: Andy Lutomirski
Date: Tue Feb 21 2017 - 14:14:23 EST

The first four patches here are intended to be straightforward
cleanups and to make a better base for Thomas' GDT series. They may
be a slight speedup, too, because they remove an STR instruction
from the VMX entry path.

The last two patches are a reasonably large speedup but need careful

FWIW, I can see lots of additional easy-ish speedups here. For example:

- The GDT reload on VM exit isn't really needed at all. Instead let's
just change the kernel limit to 0xFFFF. Doing that naively would
waste memory, but doing it carefully on top of Thomas' series would
be straightforward and almost free.

- RDMSR from MSR_GS_BASE is totally pointless.

- Once I or someone finishes the FSGSBASE series, we get a big speedup

- The LDT reload code should be split up and optimized better, I think.

Changes from v1:
- Fix some changelog typos.
- Fix the bug that Paolo found.
- Rename the helpers to make their usage more obvious.
- Move clearing __tss_limit_invalid into force_reload_TR() as a tiny
- Add a test case. It doesn't test all the machinations, but at least
it checks basic functionality.

Andy Lutomirski (7):
x86/asm: Define the kernel TSS limit in a macro
x86/kvm/vmx: Don't fetch the TSS base from the GDT
x86/kvm/vmx: Get rid of segment_base() on 64-bit kernels
x86/kvm/vmx: Simplify segment_base()
x86/asm/64: Drop __cacheline_aligned from struct x86_hw_tss
x86/kvm/vmx: Defer TR reload after VM exit
selftests/x86: Add a basic selftest for ioperm

arch/x86/include/asm/desc.h | 62 +++++++++++--
arch/x86/include/asm/processor.h | 12 ++-
arch/x86/kernel/ioport.c | 11 +++
arch/x86/kernel/process.c | 10 ++
arch/x86/kvm/vmx.c | 63 ++++++-------
tools/testing/selftests/x86/Makefile | 2 +-
tools/testing/selftests/x86/ioperm.c | 171 +++++++++++++++++++++++++++++++++++
7 files changed, 284 insertions(+), 47 deletions(-)
create mode 100644 tools/testing/selftests/x86/ioperm.c