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From: Sean Christopherson <sean.j.christopherson@intel.com>
To: Nadav Amit <nadav.amit@gmail.com>
Cc: "Paolo Bonzini" <pbonzini@redhat.com>,
	"Radim Krčmář" <rkrcmar@redhat.com>,
	kvm@vger.kernel.org
Subject: Re: [kvm-unit-tests PATCH] x86: Fix wrong test for 5-level page-table
Date: Thu, 11 Apr 2019 06:41:05 -0700	[thread overview]
Message-ID: <20190411134104.GA29427@linux.intel.com> (raw)
In-Reply-To: <20190410211334.13391-1-nadav.amit@gmail.com>

On Wed, Apr 10, 2019 at 02:13:34PM -0700, Nadav Amit wrote:
> Untested, but clearly bit 12 is the one that needs to be tested.
> 
> Signed-off-by: Nadav Amit <nadav.amit@gmail.com>
> ---
>  x86/cstart64.S | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/x86/cstart64.S b/x86/cstart64.S
> index 21db10f..8626f02 100644
> --- a/x86/cstart64.S
> +++ b/x86/cstart64.S
> @@ -243,7 +243,7 @@ start64:
>  setup_5level_page_table:
>  	/* Check if 5-level paging has already enabled */
>  	mov %cr4, %rax
> -	test $12, %eax
> +	bt $12, %eax
>  	jnz lvl5

Unfortunately BT doesn't affect RFLAGS.ZF, so 'jnz' needs to be changed
to 'jc'.  Or alternatively, do 'test $1000, %eax'.

>  
>  	pushq $32
> -- 
> 2.17.1
> 

  reply	other threads:[~2019-04-11 13:41 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-04-10 21:13 [kvm-unit-tests PATCH] x86: Fix wrong test for 5-level page-table Nadav Amit
2019-04-11 13:41 ` Sean Christopherson [this message]
2019-04-11 13:44   ` Sean Christopherson
2019-04-11 16:47   ` Nadav Amit

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