Re: [kvm-unit-tests PATCH V2 4/4] powerpc/tm: Add a test for H_CEDE while tm suspended

From: Thomas Huth <thuth@redhat.com>
To: Suraj Jitindar Singh <sjitindarsingh@gmail.com>, kvm@vger.kernel.org
Cc: pbonzini@redhat.com, rkrcmar@redhat.com, kvm-ppc@vger.kernel.org,
	lvivier@redhat.com, drjones@redhat.com
Subject: Re: [kvm-unit-tests PATCH V2 4/4] powerpc/tm: Add a test for H_CEDE while tm suspended
Date: Wed, 10 Aug 2016 13:33:34 +0200	[thread overview]
Message-ID: <283e64dd-54f0-e1c1-0b63-385b51d7dd10@redhat.com> (raw)
In-Reply-To: <1470794377-14427-4-git-send-email-sjitindarsingh@gmail.com>

On 10.08.2016 03:59, Suraj Jitindar Singh wrote:
> On Power machines if a guest cedes while a tm transaction is in the
> suspended state then the checkpointed state of the vcpu may be lost and we
> lose the cpu in the host.
> 
> Add a file for tm tests "powerpc/tm.c" and add a test to check if the fix
> has been applied to the host kernel. If this fix hasn't been applied then
> the test will never complete and the cpu will be lost. Otherwise the test
> should succeed. Since this has the ability to mess things up in the host
> mark this test as don't run by default.
> 
> Based on initial work done by: Cyril Bur <cyril.bur@au1.ibm.com>
> 
> Signed-off-by: Suraj Jitindar Singh <sjitindarsingh@gmail.com>
> ---
[...]
> +	/*
> +	 * Begin a transaction and guarantee we are in the suspend state
> +	 * before continuing
> +	 */
> +	asm volatile (	"1: tbegin.\n\t"
> +			"beq 2f\n\t"
> +			"tsuspend.\n\t"
> +			"2: tcheck cr0\n\t"
> +			"bf 2,1b"		:
> +						:
> +						: "cr0"
> +		     );

I now also tried to compile your patches, and looks like my standard GCC
cross-compiler does not know about these mnemonics yet:

/tmp/ccGEtgIa.s: Assembler messages:
/tmp/ccGEtgIa.s:96: Error: unrecognized opcode: `tbegin.'
/tmp/ccGEtgIa.s:98: Error: unrecognized opcode: `tsuspend.'
/tmp/ccGEtgIa.s:99: Error: unrecognized opcode: `tcheck'

That's happening with the standard cross-compiler which is shipping with
RHEL 7.2 (GCC 4.8.1 20130717). Could you please use ".long 0x..."
statements with the corresponding opcode values here instead, so that it
also compiles with such older versions of GCC?

 Thanks,
  Thomas