From: Paolo Bonzini <pbonzini@redhat.com>
To: "Sean Christopherson" <sean.j.christopherson@intel.com>,
"Radim Krčmář" <rkrcmar@redhat.com>,
"Thomas Gleixner" <tglx@linutronix.de>,
"Ingo Molnar" <mingo@redhat.com>,
"Borislav Petkov" <bp@alien8.de>,
x86@kernel.org, "Josh Poimboeuf" <jpoimboe@redhat.com>,
"Peter Zijlstra" <peterz@infradead.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>,
kvm@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 0/5] KVM: VMX: Optimize VMX instrs error/fault handling
Date: Wed, 25 Sep 2019 15:30:34 +0200 [thread overview]
Message-ID: <bf2d8a9d-0d7b-73da-c62e-ad3713b38e6a@redhat.com> (raw)
In-Reply-To: <20190719204110.18306-1-sean.j.christopherson@intel.com>
On 19/07/19 22:41, Sean Christopherson wrote:
> A recent commit reworked __kvm_handle_fault_on_reboot() to play nice with
> objtool. An unfortunate side effect is that JMP is now inserted after
> most VMX instructions so that the reboot macro can use an actual CALL to
> kvm_spurious_fault() instead of a funky PUSH+JMP facsimile in .fixup.
>
> Rework the low level VMX instruction helpers to handle unexpected faults
> manually instead of relying on the "fault on reboot" macro. By using
> asm-goto, most helpers can branch directly to an in-function call to
> kvm_spurious_fault(), which can then be optimized by compilers to reside
> out-of-line at the end of the function instead of inline as done by
> "fault on reboot".
>
> The net impact relative to the current code base is more or less a nop
> when building with a compiler that supports __GCC_ASM_FLAG_OUTPUTS__.
> A bunch of code that was previously in .fixup gets moved into the slow
> paths of functions, but the fast paths are more basically unchanged.
>
> Without __GCC_ASM_FLAG_OUTPUTS__, manually coding the Jcc is a net
> positive as CC_SET() without compiler support almost always generates a
> SETcc+CMP+Jcc sequence, which is now replaced with a single Jcc.
>
> A small bonus is that the Jcc instrs are hinted to predict that the VMX
> instr will be successful.
>
> v2:
> - Rebased to x86/master, commit eceffd88ca20 ("Merge branch 'x86/urgent'")
> - Reworded changelogs to reference the commit instead lkml link for
> the recent changes to __kvm_handle_fault_on_reboot().
> - Added Paolo's acks for patch 1-4
> - Added patch 5 to do more cleanup, which was made possible by rebasing
> on top of the __kvm_handle_fault_on_reboot() changes.
>
> Sean Christopherson (5):
> objtool: KVM: x86: Check kvm_rebooting in kvm_spurious_fault()
> KVM: VMX: Optimize VMX instruction error and fault handling
> KVM: VMX: Add error handling to VMREAD helper
> KVM: x86: Drop ____kvm_handle_fault_on_reboot()
> KVM: x86: Don't check kvm_rebooting in __kvm_handle_fault_on_reboot()
>
> arch/x86/include/asm/kvm_host.h | 16 ++----
> arch/x86/kvm/vmx/ops.h | 93 ++++++++++++++++++++-------------
> arch/x86/kvm/vmx/vmx.c | 42 +++++++++++++++
> arch/x86/kvm/x86.c | 3 +-
> tools/objtool/check.c | 1 -
> 5 files changed, 104 insertions(+), 51 deletions(-)
>
Queued, thanks.
Paolo
prev parent reply other threads:[~2019-09-25 13:30 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-19 20:41 [PATCH v2 0/5] KVM: VMX: Optimize VMX instrs error/fault handling Sean Christopherson
2019-07-19 20:41 ` [PATCH v2 1/5] objtool: KVM: x86: Check kvm_rebooting in kvm_spurious_fault() Sean Christopherson
2019-07-19 20:41 ` [PATCH v2 2/5] KVM: VMX: Optimize VMX instruction error and fault handling Sean Christopherson
2019-07-19 20:41 ` [PATCH v2 3/5] KVM: VMX: Add error handling to VMREAD helper Sean Christopherson
2019-07-28 19:36 ` Josh Poimboeuf
2019-07-29 9:20 ` Paolo Bonzini
2019-07-19 20:41 ` [PATCH v2 4/5] KVM: x86: Drop ____kvm_handle_fault_on_reboot() Sean Christopherson
2019-07-19 20:41 ` [PATCH v2 5/5] KVM: x86: Don't check kvm_rebooting in __kvm_handle_fault_on_reboot() Sean Christopherson
2019-07-19 21:41 ` Paolo Bonzini
2019-09-24 21:03 ` [PATCH v2 0/5] KVM: VMX: Optimize VMX instrs error/fault handling Sean Christopherson
2019-09-25 13:30 ` Paolo Bonzini [this message]
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