On 17.09.19 17:14, Paolo Bonzini wrote:
On 27/08/19 23:40, Sean Christopherson wrote:
Rework the emulator and its users to handle failure scenarios entirely
within the emulator.
{x86,kvm}_emulate_instruction() currently returns a tri-state value to
indicate success/continue, userspace exit needed, and failure. The
intent of returning EMULATE_FAIL is to let the caller handle failure in
a manner that is appropriate for the current context. In practice,
the emulator has ended up with a mixture of failure handling, i.e.
whether or not the emulator takes action on failure is dependent on the
specific flavor of emulation.
The mixed handling has proven to be rather fragile, e.g. many flows
incorrectly assume their specific flavor of emulation cannot fail or
that the emulator sets state to report the failure back to userspace.
Move everything inside the emulator, piece by piece, so that the
emulation routines can return '0' for exit to userspace and '1' for
resume the guest, just like every other VM-Exit handler.
Patch 13/14 is a tangentially related bug fix that conflicts heavily with
this series, so I tacked it on here.
Patch 14/14 documents the emulation types. I added it as a separate
patch at the very end so that the comments could reference the final
state of the code base, e.g. incorporate the rule change for using
EMULTYPE_SKIP that is introduced in patch 13/14.
v1:
- https://patchwork.kernel.org/cover/11110331/
v2:
- Collect reviews. [Vitaly and Liran]
- Squash VMware emultype changes into a single patch. [Liran]
- Add comments in VMX/SVM for VMware #GP handling. [Vitaly]
- Tack on the EPT misconfig bug fix.
- Add a patch to comment/document the emultypes. [Liran]
Sean Christopherson (14):
KVM: x86: Relocate MMIO exit stats counting
KVM: x86: Clean up handle_emulation_failure()
KVM: x86: Refactor kvm_vcpu_do_singlestep() to remove out param
KVM: x86: Don't attempt VMWare emulation on #GP with non-zero error
code
KVM: x86: Move #GP injection for VMware into x86_emulate_instruction()
KVM: x86: Add explicit flag for forced emulation on #UD
KVM: x86: Move #UD injection for failed emulation into emulation code
KVM: x86: Exit to userspace on emulation skip failure
KVM: x86: Handle emulation failure directly in kvm_task_switch()
KVM: x86: Move triple fault request into RM int injection
KVM: VMX: Remove EMULATE_FAIL handling in handle_invalid_guest_state()
KVM: x86: Remove emulation_result enums, EMULATE_{DONE,FAIL,USER_EXIT}
KVM: VMX: Handle single-step #DB for EMULTYPE_SKIP on EPT misconfig
KVM: x86: Add comments to document various emulation types
arch/x86/include/asm/kvm_host.h | 40 +++++++--
arch/x86/kvm/mmu.c | 16 +---
arch/x86/kvm/svm.c | 62 ++++++--------
arch/x86/kvm/vmx/vmx.c | 147 +++++++++++++-------------------
arch/x86/kvm/x86.c | 133 ++++++++++++++++-------------
arch/x86/kvm/x86.h | 2 +-
6 files changed, 195 insertions(+), 205 deletions(-)
Queued, thanks (a couple conflicts had to be sorted out, but nothing
requiring a respin).
Ugh, I just stumbled over this commit. Is this really the right
direction to move towards?
I appreciate the move to reduce the emulator logic from the many-fold
enum into a simple binary "worked" or "needs a user space exit". But are
"0" and "1" really the right names for that? I find the readability of
the current intercept handlers bad enough, trickling that into even more
code sounds like a situation that will decrease readability even more.
Why can't we just use names throughout? Something like
enum kvm_return {
KVM_RET_USER_EXIT = 0,
KVM_RET_GUEST = 1,
};
and then consistently use them as return values? That way anyone who has
not worked on kvm before can still make sense of the code.
Alex
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