| Message ID | 20181220202518.21442-1-sean.j.christopherson@intel.com (mailing list archive) |
|---|---|
| Headers | show |
| Series | KVM: VMX: Clean up VM-Enter/VM-Exit asm code | expand |
Despite all but one patch being KVM cleanup, that one outlier is the
true catalyst for this series. The outlier, patch 3/11, removes an
optimization tweak from the __noclone macro that was added by commit
95272c29378e ("compiler-gcc: disable -ftracer for __noclone functions")
to workaround a compiler error in KVM's esoteric VMX assembly code.
Unbeknownst at the time, using the __optimize__ attribute causes GCC
to reset to -O2 optimization defaults, which has several unintended
side effects including dropping -fno-omit-frame-pointer and preventing
GCC from properly inlining function calls due to the functions having
incompatible optimization attributes.
Patches 1/11 and 2/11 fix the offending KVM code and eliminate its
usage of __noclone, allowing patch 3/11 to remove "no-tracer" from the
__noclone macro.
Patches 4/11 and beyond are a mix of cleanup, fixes and optimizations
for a variety of low hanging fruit that were (unsurprisingly) revealed
when revisiting KVM's inline assembly blob.
FYI, I cc'd everyone involved for all patches up until the -ftracer
revert, after that I limited the cc/to list to KVM folks.
Sean Christopherson (11):
KVM: VMX: Explicitly reference RCX as the vmx_vcpu pointer in asm
blobs
KVM: VMX: Move VM-Enter + VM-Exit handling to non-inline sub-routines
Revert "compiler-gcc: disable -ftracer for __noclone functions"
KVM: VMX: Modify only RSP when creating a placeholder for guest's RCX
KVM: VMX: Save RSI to an unused output in vmx_vcpu_run() asm blob
KVM: VMX: Manually load RDX in vmx_vcpu_run() asm blob
KVM: VMX: Let the compiler save/load RDX around VM-Enter
KVM: nVMX: Cache host_rsp on a per-VMCS basis
KVM: nVMX: Add eVMCS support to nested_vmx_check_vmentry_hw()
KVM: VMX: Add macros to handle HOST_RSP updates at VM-Enter
KVM: nVMX: Remove a rogue "rax" clobber from
nested_vmx_check_vmentry_hw()
arch/x86/kvm/Makefile | 2 +-
arch/x86/kvm/vmx/nested.c | 57 ++++---------
arch/x86/kvm/vmx/vmcs.h | 1 +
arch/x86/kvm/vmx/vmenter.S | 57 +++++++++++++
arch/x86/kvm/vmx/vmx.c | 127 +++++++++++++---------------
arch/x86/kvm/vmx/vmx.h | 30 ++++++-
include/linux/compiler_attributes.h | 8 +-
7 files changed, 164 insertions(+), 118 deletions(-)
create mode 100644 arch/x86/kvm/vmx/vmenter.S
Please ignore this duplicate, had a typo in my send script. Sorry for the noise.
On Thu, Dec 20, 2018 at 12:25:15PM -0800, Sean Christopherson wrote: > Despite all but one patch being KVM cleanup, that one outlier is the > true catalyst for this series. The outlier, patch 3/11, removes an > optimization tweak from the __noclone macro that was added by commit > 95272c29378e ("compiler-gcc: disable -ftracer for __noclone functions") > to workaround a compiler error in KVM's esoteric VMX assembly code. Patches look good to me. Reviewed-by: Andi Kleen <ak@linux.intel.com> -Andi
On 20/12/18 21:25, Sean Christopherson wrote: > Despite all but one patch being KVM cleanup, that one outlier is the > true catalyst for this series. The outlier, patch 3/11, removes an > optimization tweak from the __noclone macro that was added by commit > 95272c29378e ("compiler-gcc: disable -ftracer for __noclone functions") > to workaround a compiler error in KVM's esoteric VMX assembly code. > > Unbeknownst at the time, using the __optimize__ attribute causes GCC > to reset to -O2 optimization defaults, which has several unintended > side effects including dropping -fno-omit-frame-pointer and preventing > GCC from properly inlining function calls due to the functions having > incompatible optimization attributes. > > Patches 1/11 and 2/11 fix the offending KVM code and eliminate its > usage of __noclone, allowing patch 3/11 to remove "no-tracer" from the > __noclone macro. Very nice! I'm applying 1-3 right away, while the rest should wait for 4.22. Paolo
Despite all but one patch being KVM cleanup, that one outlier is the true catalyst for this series. The outlier, patch 3/11, removes an optimization tweak from the __noclone macro that was added by commit 95272c29378e ("compiler-gcc: disable -ftracer for __noclone functions") to workaround a compiler error in KVM's esoteric VMX assembly code. Unbeknownst at the time, using the __optimize__ attribute causes GCC to reset to -O2 optimization defaults, which has several unintended side effects including dropping -fno-omit-frame-pointer and preventing GCC from properly inlining function calls due to the functions having incompatible optimization attributes. Patches 1/11 and 2/11 fix the offending KVM code and eliminate its usage of __noclone, allowing patch 3/11 to remove "no-tracer" from the __noclone macro. Patches 4/11 and beyond are a mix of cleanup, fixes and optimizations for a variety of low hanging fruit that were (unsurprisingly) revealed when revisiting KVM's inline assembly blob. FYI, I cc'd everyone involved for all patches up until the -ftracer revert, after that I limited the cc/to list to KVM folks. Sean Christopherson (11): KVM: VMX: Explicitly reference RCX as the vmx_vcpu pointer in asm blobs KVM: VMX: Move VM-Enter + VM-Exit handling to non-inline sub-routines Revert "compiler-gcc: disable -ftracer for __noclone functions" KVM: VMX: Modify only RSP when creating a placeholder for guest's RCX KVM: VMX: Save RSI to an unused output in vmx_vcpu_run() asm blob KVM: VMX: Manually load RDX in vmx_vcpu_run() asm blob KVM: VMX: Let the compiler save/load RDX around VM-Enter KVM: nVMX: Cache host_rsp on a per-VMCS basis KVM: nVMX: Add eVMCS support to nested_vmx_check_vmentry_hw() KVM: VMX: Add macros to handle HOST_RSP updates at VM-Enter KVM: nVMX: Remove a rogue "rax" clobber from nested_vmx_check_vmentry_hw() arch/x86/kvm/Makefile | 2 +- arch/x86/kvm/vmx/nested.c | 57 ++++--------- arch/x86/kvm/vmx/vmcs.h | 1 + arch/x86/kvm/vmx/vmenter.S | 57 +++++++++++++ arch/x86/kvm/vmx/vmx.c | 127 +++++++++++++--------------- arch/x86/kvm/vmx/vmx.h | 30 ++++++- include/linux/compiler_attributes.h | 8 +- 7 files changed, 164 insertions(+), 118 deletions(-) create mode 100644 arch/x86/kvm/vmx/vmenter.S