Re: [PATCH 0/12] KVM: SVM: Add support for VMCB state caching

Joerg Roedel
2010-12-07T08:26:23Z

On Mon, Dec 06, 2010 at 05:49:55PM -0200, Marcelo Tosatti wrote:
> On Fri, Dec 03, 2010 at 11:45:47AM +0100, Joerg Roedel wrote:
> > Hi Avi, Hi Marcelo,
> >
> > here is a patch-set which adds support for VMCB state caching to KVM.
> > This is a new CPU feature where software can mark certain parts of the
> > VMCB as unchanged since the last vmexit and the hardware can then avoid
> > reloading these parts from memory.
> >
> > The feature is implemented downwards-compatible in hardware, so a 0-bit
> > means the state has changed and needs to be reloaded. This makes it
> > possible to implement the bits without checking for the feature, as done
> > in this patch-set (another reason is that the check is as expensive as
> > clearing the bit). Processors which do not implement VMCB state
> > caching just ignore these bits.
> >
> > These patches were tested with multiple guests (Windows, Linux, also in
> > parallel) and also with nested-svm.
> >
> > The patches apply on-top of the intercept mask wrapping patch-set I sent
> > earlier this week. Your feedback is appreciated.
> >
> > Regards,
> > Joerg
> >
> > arch/x86/include/asm/svm.h | 6 +++-
> > arch/x86/kvm/svm.c | 70 ++++++++++++++++++++++++++++++++++++++++++++
> > 2 files changed, 75 insertions(+), 1 deletions(-)
> >
> > Joerg Roedel (12):
> > KVM: SVM: Add clean-bits infrastructure code
> > KVM: SVM: Add clean-bit for intercetps, tsc-offset and pause filter count
> > KVM: SVM: Add clean-bit for IOPM_BASE and MSRPM_BASE
> > KVM: SVM: Add clean-bit for the ASID
> > KVM: SVM: Add clean-bit for interrupt state
> > KVM: SVM: Add clean-bit for NPT state
> > KVM: SVM: Add clean-bit for control registers
> > KVM: SVM: Add clean-bit for DR6 and DR7
> > KVM: SVM: Add clean-bit for GDT and IDT
> > KVM: SVM: Add clean-bit for Segements and CPL
> > KVM: SVM: Add clean-bit for CR2 register
> > KVM: SVM: Add clean-bit for LBR state
>
> Wouldnt it be good to wrap assignment of field & dirty bit update
> in wrappers, for long term maintainability?

Right. I did that for the intercept masks already. Most other stuff is
also already wrapped. But there is certainly still room for improvement.

Joerg