linux-kernel - Re: [PATCH 2/2] x86/cpu/vmware: Fix platform detection VMWARE

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Date:   Fri, 18 Oct 2019 09:38:27 -0700
From:   Sean Christopherson <sean.j.christopherson@...el.com>
To:     Thomas Hellström (VMware) 
        <thomas_os@...pmail.org>
Cc:     linux-kernel@...r.kernel.org,
        Thomas Hellstrom <thellstrom@...are.com>,
        "H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>, x86-ml <x86@...nel.org>,
        Borislav Petkov <bp@...e.de>
Subject: Re: [PATCH 2/2] x86/cpu/vmware: Fix platform detection VMWARE_PORT
 macro

On Fri, Oct 18, 2019 at 03:40:52PM +0200, Thomas Hellström (VMware) wrote:
> From: Thomas Hellstrom <thellstrom@...are.com>
> 
> The platform detection VMWARE_PORT macro uses the VMWARE_HYPERVISOR_PORT
> definition, but expects it to be an integer. However, when it was moved
> to the new vmware.h include file, it was changed to be a string to better
> fit into the VMWARE_HYPERCALL set of macros. This obviously breaks the
> platform detection VMWARE_PORT functionality.
> 
> Change the VMWARE_HYPERVISOR_PORT and VMWARE_HYPERVISOR_PORT_HB
> definitions to be integers, and use __stringify() for their stringified
> form when needed.
> 
> Fixes: b4dd4f6e3648 ("Add a header file for hypercall definitions")
> Signed-off-by: Thomas Hellstrom <thellstrom@...are.com>
> Cc: "H. Peter Anvin" <hpa@...or.com>
> Cc: Ingo Molnar <mingo@...hat.com>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: x86-ml <x86@...nel.org>
> Cc: Borislav Petkov <bp@...e.de>
> ---
>  arch/x86/include/asm/vmware.h | 13 ++++++++-----
>  1 file changed, 8 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/x86/include/asm/vmware.h b/arch/x86/include/asm/vmware.h
> index f5fbe3778aef..d20eda0c6ed8 100644
> --- a/arch/x86/include/asm/vmware.h
> +++ b/arch/x86/include/asm/vmware.h
> @@ -4,6 +4,7 @@
>  
>  #include <asm/cpufeatures.h>
>  #include <asm/alternative.h>
> +#include <linux/stringify.h>
>  
>  /*
>   * The hypercall definitions differ in the low word of the %edx argument
> @@ -20,8 +21,8 @@
>   */
>  
>  /* Old port-based version */
> -#define VMWARE_HYPERVISOR_PORT    "0x5658"
> -#define VMWARE_HYPERVISOR_PORT_HB "0x5659"
> +#define VMWARE_HYPERVISOR_PORT    0x5658
> +#define VMWARE_HYPERVISOR_PORT_HB 0x5659
>  
>  /* Current vmcall / vmmcall version */
>  #define VMWARE_HYPERVISOR_HB   BIT(0)
> @@ -29,7 +30,7 @@
>  
>  /* The low bandwidth call. The low word of edx is presumed clear. */
>  #define VMWARE_HYPERCALL						\
> -	ALTERNATIVE_2("movw $" VMWARE_HYPERVISOR_PORT			\
> +	ALTERNATIVE_2("movw $" __stringify(VMWARE_HYPERVISOR_PORT)	\
>  		      ", %%dx; inl (%%dx), %%eax",			\
>  		      "vmcall", X86_FEATURE_VMCALL,			\
>  		      "vmmcall", X86_FEATURE_VMW_VMMCALL)
> @@ -39,7 +40,8 @@
>   * HB and OUT bits set.
>   */
>  #define VMWARE_HYPERCALL_HB_OUT						\
> -	ALTERNATIVE_2("movw $" VMWARE_HYPERVISOR_PORT_HB ", %%dx; rep outsb", \
> +	ALTERNATIVE_2("movw $" __stringify(VMWARE_HYPERVISOR_PORT_HB)	\
> +		      ", %%dx; rep outsb",				\
>  		      "vmcall", X86_FEATURE_VMCALL,			\
>  		      "vmmcall", X86_FEATURE_VMW_VMMCALL)
>  
> @@ -48,7 +50,8 @@
>   * HB bit set.
>   */
>  #define VMWARE_HYPERCALL_HB_IN						\
> -	ALTERNATIVE_2("movw $" VMWARE_HYPERVISOR_PORT_HB ", %%dx; rep insb", \
> +	ALTERNATIVE_2("movw $" __stringify(VMWARE_HYPERVISOR_PORT_HB)	\
> +		      ", %%dx; rep insb",				\

Same comment on wrapping in the middle of an instruction.  Wrapping after
movw will stick out, but only by a char or two.

>  		      "vmcall", X86_FEATURE_VMCALL,			\
>  		      "vmmcall", X86_FEATURE_VMW_VMMCALL)
>  #endif
> -- 
> 2.21.0
>