linux/arch/x86
Sean Christopherson 678e315e78 KVM: vmx: add dedicated utility to access guest's kernel_gs_base
When lazy save/restore of MSR_KERNEL_GS_BASE was introduced[1], the
MSR was intercepted in all modes and was only restored for the host
when the guest is in 64-bit mode.  So at the time, going through the
full host restore prior to accessing MSR_KERNEL_GS_BASE was necessary
to load host state and was not a significant waste of cycles.

Later, MSR_KERNEL_GS_BASE interception was disabled for a 64-bit
guest[2], and then unconditionally saved/restored for the host[3].
As a result, loading full host state is overkill for accesses to
MSR_KERNEL_GS_BASE, and completely unnecessary when the guest is
not in 64-bit mode.

Add a dedicated utility to read/write the guest's MSR_KERNEL_GS_BASE
(outside of the save/restore flow) to minimize the overhead incurred
when accessing the MSR.  When setting EFER, only decache the MSR if
the new EFER will disable long mode.

Removing out-of-band usage of vmx_load_host_state() also eliminates,
or at least reduces, potential corner cases in its usage, which in
turn will (hopefuly) make it easier to reason about future changes
to the save/restore flow, e.g. optimization of saving host state.

[1] commit 44ea2b1758 ("KVM: VMX: Move MSR_KERNEL_GS_BASE out of the vmx
                                    autoload msr area")
[2] commit 5897297bc2 ("KVM: VMX: Don't intercept MSR_KERNEL_GS_BASE")
[3] commit c8770e7ba6 ("KVM: VMX: Fix host userspace gsbase corruption")

Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2018-08-06 17:59:12 +02:00
..
boot efi/x86: Fix mixed mode reboot loop by removing pointless call to PciIo->Attributes() 2018-07-11 13:15:21 +02:00
configs x86/unwind: Rename unwinder config options to 'CONFIG_UNWINDER_*' 2017-10-14 10:12:12 +02:00
crypto crypto: x86 - Add missing RETs 2018-07-01 23:33:20 +08:00
entry x86/entry/64/compat: Fix "x86/entry/64/compat: Preserve r8-r11 in int $0x80" 2018-06-27 09:35:40 +02:00
events x86/events/intel/ds: Fix bts_interrupt_threshold alignment 2018-07-15 11:38:44 +02:00
hyperv X86/Hyper-V: Add hyperv_nested_flush_guest_mapping ftrace support 2018-08-06 17:59:05 +02:00
ia32 syscalls/x86: auto-create compat_sys_*() prototypes 2018-04-02 20:16:18 +02:00
include KVM: x86: Add tlb remote flush callback in kvm_x86_ops. 2018-08-06 17:59:06 +02:00
kernel x86/kvm: Don't use pvqspinlock code if only 1 vCPU 2018-08-06 17:59:04 +02:00
kvm KVM: vmx: add dedicated utility to access guest's kernel_gs_base 2018-08-06 17:59:12 +02:00
lib libnvdimm for 4.18 2018-06-08 17:21:52 -07:00
math-emu License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
mm x86/mm: Clean up the printk()s in show_fault_oops() 2018-06-27 14:08:11 +02:00
net treewide: kmalloc() -> kmalloc_array() 2018-06-12 16:19:22 -07:00
oprofile x86/oprofile: Fix bogus GCC-8 warning in nmi_setup() 2018-02-21 09:54:17 +01:00
pci treewide: kzalloc() -> kcalloc() 2018-06-12 16:19:22 -07:00
platform x86/efi: Fix efi_call_phys_epilog() with CONFIG_X86_5LEVEL=y 2018-06-27 09:52:52 +02:00
power x86/mm: Stop pretending pgtable_l5_enabled is a variable 2018-05-19 11:56:57 +02:00
purgatory x86/purgatory: add missing FORCE to Makefile target 2018-07-14 11:11:09 -07:00
ras License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
realmode x86-64/realmode: Add instruction suffix 2018-02-20 09:33:41 +01:00
tools x86: Treat R_X86_64_PLT32 as R_X86_64_PC32 2018-02-22 09:01:10 -08:00
um Kconfig updates for v4.18 2018-06-06 11:31:45 -07:00
video
xen xen: fixes for 4.18-rc5 2018-07-14 12:30:13 -07:00
.gitignore x86/build: Add arch/x86/tools/insn_decoder_test to .gitignore 2018-02-13 14:10:29 +01:00
Kbuild Merge branch 'x86-platform-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2017-09-07 09:25:15 -07:00
Kconfig x86/asm/memcpy_mcsafe: Fix copy_to_user_mcsafe() exception handling 2018-07-16 00:05:05 +02:00
Kconfig.cpu Merge branch 'x86-pti-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2018-03-25 07:36:02 -10:00
Kconfig.debug x86, nfit_test: Add unit test for memcpy_mcsafe() 2018-05-22 23:18:31 -07:00
Makefile Merge branch 'linus' into x86/urgent 2018-06-22 21:20:35 +02:00
Makefile_32.cpu License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
Makefile.um License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00