[kvm-unit-tests PATCH] x86: Use "-cpu host" for PCID tests

[kvm-unit-tests PATCH] x86: Use "-cpu host" for PCID tests

[Sean Christopherson]

Use the host CPU model for the PCID tests to allow testing the various
combinations of PCID and INVPCID enabled/disabled without having to
manually change the kvm-unit-tests command line.  I.e. give users the
option of changing the command line *OR* running on a (virtual) CPU
with or without PCID and/or INVPCID.

Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
---
 x86/unittests.cfg | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/x86/unittests.cfg b/x86/unittests.cfg
index aae1523..25f4535 100644
--- a/x86/unittests.cfg
+++ b/x86/unittests.cfg
@@ -228,7 +228,7 @@ extra_params = --append "10000000 `date +%s`"
 
 [pcid]
 file = pcid.flat
-extra_params = -cpu qemu64,+pcid
+extra_params = -cpu host
 arch = x86_64
 
 [rdpru]
-- 
2.24.1

Re: [kvm-unit-tests PATCH] x86: Use "-cpu host" for PCID tests

[Vitaly Kuznetsov]

Sean Christopherson <sean.j.christopherson@intel.com> writes:

> Use the host CPU model for the PCID tests to allow testing the various
> combinations of PCID and INVPCID enabled/disabled without having to
> manually change the kvm-unit-tests command line.  I.e. give users the
> option of changing the command line *OR* running on a (virtual) CPU
> with or without PCID and/or INVPCID.
>
> Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
> ---
>  x86/unittests.cfg | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/x86/unittests.cfg b/x86/unittests.cfg
> index aae1523..25f4535 100644
> --- a/x86/unittests.cfg
> +++ b/x86/unittests.cfg
> @@ -228,7 +228,7 @@ extra_params = --append "10000000 `date +%s`"
>  
>  [pcid]
>  file = pcid.flat
> -extra_params = -cpu qemu64,+pcid
> +extra_params = -cpu host
>  arch = x86_64
>  
>  [rdpru]

Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com>

Actually, is there any reason for *not* using '-cpu host' in any of the
tests?

-- 
Vitaly

Re: [kvm-unit-tests PATCH] x86: Use "-cpu host" for PCID tests

[Sean Christopherson]

On Wed, Feb 05, 2020 at 12:37:11PM +0100, Vitaly Kuznetsov wrote:
> Sean Christopherson <sean.j.christopherson@intel.com> writes:
> 
> > Use the host CPU model for the PCID tests to allow testing the various
> > combinations of PCID and INVPCID enabled/disabled without having to
> > manually change the kvm-unit-tests command line.  I.e. give users the
> > option of changing the command line *OR* running on a (virtual) CPU
> > with or without PCID and/or INVPCID.
> >
> > Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
> > ---
> >  x86/unittests.cfg | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/x86/unittests.cfg b/x86/unittests.cfg
> > index aae1523..25f4535 100644
> > --- a/x86/unittests.cfg
> > +++ b/x86/unittests.cfg
> > @@ -228,7 +228,7 @@ extra_params = --append "10000000 `date +%s`"
> >  
> >  [pcid]
> >  file = pcid.flat
> > -extra_params = -cpu qemu64,+pcid
> > +extra_params = -cpu host
> >  arch = x86_64
> >  
> >  [rdpru]
> 
> Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com>
> 
> Actually, is there any reason for *not* using '-cpu host' in any of the
> tests?

Emulation tests, e.g. for UMIP, will want "-cpu <base>,+<feature>", but I
can't think of any reason why <base> shouldn't be host.

Re: [kvm-unit-tests PATCH] x86: Use "-cpu host" for PCID tests

[Paolo Bonzini]

On 04/02/20 20:48, Sean Christopherson wrote:
> Use the host CPU model for the PCID tests to allow testing the various
> combinations of PCID and INVPCID enabled/disabled without having to
> manually change the kvm-unit-tests command line.  I.e. give users the
> option of changing the command line *OR* running on a (virtual) CPU
> with or without PCID and/or INVPCID.

I don't understand. :)

> Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
> ---
>  x86/unittests.cfg | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/x86/unittests.cfg b/x86/unittests.cfg
> index aae1523..25f4535 100644
> --- a/x86/unittests.cfg
> +++ b/x86/unittests.cfg
> @@ -228,7 +228,7 @@ extra_params = --append "10000000 `date +%s`"
>  
>  [pcid]
>  file = pcid.flat
> -extra_params = -cpu qemu64,+pcid
> +extra_params = -cpu host
>  arch = x86_64
>  
>  [rdpru]
> 

The main reason not to use "-cpu host" is that it is not supported by
QEMU TCG (binary translation mode).  But there is no reason not to use
"-cpu max", which works with TCG and is synonym with "-cpu host" on KVM. :)

Paolo

Paolo

Re: [kvm-unit-tests PATCH] x86: Use "-cpu host" for PCID tests

[Sean Christopherson]

On Wed, Feb 05, 2020 at 04:26:40PM +0100, Paolo Bonzini wrote:
> On 04/02/20 20:48, Sean Christopherson wrote:
> > Use the host CPU model for the PCID tests to allow testing the various
> > combinations of PCID and INVPCID enabled/disabled without having to
> > manually change the kvm-unit-tests command line.  I.e. give users the
> > option of changing the command line *OR* running on a (virtual) CPU
> > with or without PCID and/or INVPCID.
> 
> I don't understand. :)

I was trying to test a change in the code that clears INVPCID in guest's
CPUID if PCID isn't supported.  To do that, I ran the PCID unit test in L1,
using L0 Qemu to hide PCID and/or INVPCID from L1 to iterate over the four
combinations of PCID and INVPCID being enabled/disabled.  But the test in
L1 never exercised INVPCID=y because unittest.cfg runs with the test with
"-cpu=qemu64,+pcid".

By using qemu64, the only way to test INVPCID=y is to manually run the test
a different "-cpu..." command.  The idea behind "-cpu=host" is to enable
running different combinations of the test in L1 by hiding features from L1
instead of by running the test with different commands.

In other words, if I create an L1 with PCID=y and INVPCID=y, I expect that
running the as-configured PCID unit tests would actually test PCID=Y and
INVPCID=y.