linux-kernel - Re: [PATCH v6 2/4] x86/tests: Add tests for AMD SEV-ES #VC handling Add KUnit based tests to validate Linux's VC handling for instructions cpuid and wbinvd. These tests: 1. install a kretprobe on the #VC handler (sev_es_ghcb_hv_call, to access GHCB before/after the resulting VMGEXIT). 2. trigger an NAE by executing either cpuid or wbinvd. 3. check that the kretprobe was hit with the right exit

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Date:   Wed, 8 Jun 2022 17:45:03 +0200
From:   Vasant Karasulli <vkarasulli@...e.de>
To:     Sean Christopherson <seanjc@...gle.com>
Cc:     linux-kernel@...r.kernel.org, jroedel@...e.de, kvm@...r.kernel.org,
        bp@...en8.de, x86@...nel.org, thomas.lendacky@....com
Subject: Re: [PATCH v6 2/4] x86/tests: Add tests for AMD SEV-ES #VC handling
 Add KUnit based tests to validate Linux's VC handling for instructions cpuid
 and wbinvd. These tests: 1. install a kretprobe on the #VC handler
 (sev_es_ghcb_hv_call, to access GHCB before/after the resulting VMGEXIT). 2.
 trigger an NAE by executing either cpuid or wbinvd. 3. check that the
 kretprobe was hit with the right exit_code available in GHCB.

On Mi 08-06-22 14:35:55, Sean Christopherson wrote:
> On Wed, Jun 08, 2022, Vasant Karasulli wrote:
> > On Mi 06-04-22 01:22:55, Sean Christopherson wrote:
> > > > +	if (ret) {
> > > > +		kunit_info(test, "Could not register kretprobe. Skipping.");
> > > > +		goto out;
> > > > +	}
> > > > +
> > > > +	test->priv = kunit_kzalloc(test, sizeof(u64), GFP_KERNEL);
> > >
> > > Allocating 8 bytes and storing the pointer an 8-byte field is rather pointless :-)
> > >
> >
> > Actually it's necessary to allocate memory to test->priv before using according to
> > https://www.kernel.org/doc/html/latest/dev-tools/kunit/tips.html
>
> If priv points at structure of some form, sure, but you're storing a simple value.

Yes, I agree. The reason it was done this way I guess is that type of priv is a
void pointer and storing a u64 value results in a compiler warning:
cast from pointer to integer of different size [-Wpointer-to-int-cast].

Thanks,
Vasant Karasulli
Kernel generalist
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