linux-kernel - Re: [PATCH 3/6] x86/kvm/emulate: Avoid RET for fastops

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Message-ID: <aBDcr49ez9B8u9qa@google.com>
Date: Tue, 29 Apr 2025 07:05:35 -0700
From: Sean Christopherson <seanjc@...gle.com>
To: Peter Zijlstra <peterz@...radead.org>
Cc: Josh Poimboeuf <jpoimboe@...nel.org>, x86@...nel.org, kys@...rosoft.com, 
	haiyangz@...rosoft.com, wei.liu@...nel.org, decui@...rosoft.com, 
	tglx@...utronix.de, mingo@...hat.com, bp@...en8.de, 
	dave.hansen@...ux.intel.com, hpa@...or.com, pawan.kumar.gupta@...ux.intel.com, 
	pbonzini@...hat.com, ardb@...nel.org, kees@...nel.org, 
	Arnd Bergmann <arnd@...db.de>, gregkh@...uxfoundation.org, linux-hyperv@...r.kernel.org, 
	linux-kernel@...r.kernel.org, kvm@...r.kernel.org, linux-efi@...r.kernel.org, 
	samitolvanen@...gle.com, ojeda@...nel.org
Subject: Re: [PATCH 3/6] x86/kvm/emulate: Avoid RET for fastops

On Tue, Apr 29, 2025, Peter Zijlstra wrote:
> On Mon, Apr 28, 2025 at 10:13:31AM -0700, Sean Christopherson wrote:
> > On Sat, Apr 26, 2025, Peter Zijlstra wrote:
> > > On Wed, Apr 16, 2025 at 10:38:59AM +0200, Peter Zijlstra wrote:
> > > 
> > > > Yeah, I finally got there. I'll go cook up something else.
> > > 
> > > Sean, Paolo, can I once again ask how best to test this fastop crud?
> > 
> > Apply the below, build KVM selftests, 
> 
> Patch applied, my own hackery applied, host kernel built and booted,
> foce_emulation_prefix set, but now I'm stuck at this seemingly simple
> step..
> 
> $ cd tools/testing/selftests/kvm/
> $ make
> ... metric ton of fail ...
> 
> Clearly I'm doing something wrong :/

Did you install headers in the top level directory?  I.e. make headers_install.
The selftests build system was change a while back to require users to manually
install headers (I forget why, but it is indeed annoying).