linux-kernel - Re: [PATCH v2 1/4] x86/vmware: Update platform detection code for VMCALL/VMMCALL hypercalls

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Date:   Wed, 28 Aug 2019 09:45:19 +0200
From:   Thomas Hellström (VMware) 
        <thomas_os@...pmail.org>
To:     Borislav Petkov <bp@...en8.de>
Cc:     linux-kernel@...r.kernel.org, pv-drivers@...are.com,
        linux-graphics-maintainer@...are.com,
        Thomas Hellstrom <thellstrom@...are.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        dri-devel@...ts.freedekstop.org, Doug Covelli <dcovelli@...are.com>
Subject: Re: [PATCH v2 1/4] x86/vmware: Update platform detection code for
 VMCALL/VMMCALL hypercalls

On 8/27/19 2:56 PM, Borislav Petkov wrote:
>
> Also, you could restructure that function something like this to save yourself
> an indentation level or two and make it more easily readable:
>
> static uint32_t __init vmware_platform(void)
> {
>          unsigned int hyper_vendor_id[3];
>          unsigned int eax;
>
>          if (!boot_cpu_has(X86_FEATURE_HYPERVISOR)) {
>                  if (dmi_available && dmi_name_in_serial("VMware") && __vmware_platform())
>                          return 1;


Hmm, we're missing a return 0; here. The number of return points and the 
moved up variable declarations worries me a little. I'll see if I can 
clean this up a bit, but would prefer to make a follow-up patch in that 
case.

/Thomas


>          }
>
>          cpuid(CPUID_VMWARE_INFO_LEAF, &eax, &hyper_vendor_id[0],
>                &hyper_vendor_id[1], &hyper_vendor_id[2]);
>
>          if (!memcmp(hyper_vendor_id, "VMwareVMware", 12)) {
>                  if (eax >= CPUID_VMWARE_FEATURES_LEAF)
>                          vmware_hypercall_mode = vmware_select_hypercall();
>
>                  pr_info("hypercall mode: 0x%02x\n", (unsigned int) vmware_hypercall_mode);
>
>                  return CPUID_VMWARE_INFO_LEAF;
>          }
>          return 0;
> }
>