Linux Virtualization - Oct 2016 - [RESEND PATCH 1/3] x86/vmware: Use tsc_khz value for calibrate_cpu()

I believe our trademark guidelines say we aren't supposed to use VMware as a
noun to mean a product, only to mean the company.  So we can say "running
on
VMware ESXi" or "running in a VMware virtual machine", but
"running on VMware"
is wrong.  There is supposedly some good legal reason for this related to
keeping our trademark.

On Tue, 25 Oct 2016 22:26:00 -0700, Alexey Makhalov <amakhalov at
vmware.com>
wrote:
> Add basic paravirt support:
>  1. set pv_info.name to "VMware" to have proper boot log message
> 	Booting paravirtualized kernel on VMware
>     instead of "... on bare hardware"
>  2. set pv_cpu_ops.io_delay() to empty function - paravirt_nop() to
>     avoid vm-exits on IO delays.
> 
> Signed-off-by: Alexey Makhalov <amakhalov at vmware.com>
> Acked-by: Alok N Kataria <akataria at vmware.com>
> ---
>  arch/x86/kernel/cpu/vmware.c | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
> 
> diff --git a/arch/x86/kernel/cpu/vmware.c b/arch/x86/kernel/cpu/vmware.c
> index 480790f..e3fb320 100644
> --- a/arch/x86/kernel/cpu/vmware.c
> +++ b/arch/x86/kernel/cpu/vmware.c
> @@ -61,6 +61,16 @@ static unsigned long vmware_get_tsc_khz(void)
>  	return vmware_tsc_khz;
>  }
>  
> +#ifdef CONFIG_PARAVIRT
> +static void __init vmware_paravirt_ops_setup(void)
> +{
> +	pv_info.name = "VMware";
> +	pv_cpu_ops.io_delay = paravirt_nop;
> +}
> +#else
> +#define vmware_paravirt_ops_setup() do {} while (0)
> +#endif
> +
>  static void __init vmware_platform_setup(void)
>  {
>  	uint32_t eax, ebx, ecx, edx;
> @@ -94,6 +104,8 @@ static void __init vmware_platform_setup(void)
>  	} else {
>  		pr_warn("Failed to get TSC freq from the hypervisor\n");
>  	}
> +
> +	vmware_paravirt_ops_setup();
>  }
>  
>  /*


-- 
Tim Mann                  | work: mann at vmware.com  home: tim at tim-mann.org
VMware Sr. Staff Engineer | http://www.vmware.com  http://tim-mann.org

On Wed, 26 Oct 2016, Tim Mann wrote:
> I believe our trademark guidelines say we aren't supposed to use VMware
as a
> noun to mean a product, only to mean the company.  So we can say
"running on
> VMware ESXi" or "running in a VMware virtual machine", but
"running on VMware"
> is wrong.  There is supposedly some good legal reason for this related to
> keeping our trademark.
Please sort that out internally and resend the whole lot when this is
resolved.

Thanks,

	tglx

After aa297292d708, there are separate native calibrations for cpu_khz and
tsc_khz. The code sets x86_platform.calibrate_cpu to native_calibrate_cpu()
which looks in cpuid leaf 0x16 or msrs for the cpu frequency. Since we keep
the tsc_khz constant (even after vmotion), the cpu_khz and tsc_khz may
start diverging.

tsc_init() now does

	cpu_khz = x86_platform.calibrate_cpu();
	tsc_khz = x86_platform.calibrate_tsc();
	if (tsc_khz == 0)
		tsc_khz = cpu_khz;
	else if (abs(cpu_khz - tsc_khz) * 10 > tsc_khz)
		cpu_khz = tsc_khz;

We want the cpu_khz and tsc_khz to be sync even if they diverge less then
10%.
This patch resolves this issue by setting x86_platform.calibrate_cpu to
vmware_get_tsc_khz().

Signed-off-by: Alexey Makhalov <amakhalov at vmware.com>
Acked-by: Alok N Kataria <akataria at vmware.com>
---
 arch/x86/kernel/cpu/vmware.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/x86/kernel/cpu/vmware.c b/arch/x86/kernel/cpu/vmware.c
index 4e34da4b..480790f 100644
--- a/arch/x86/kernel/cpu/vmware.c
+++ b/arch/x86/kernel/cpu/vmware.c
@@ -83,6 +83,7 @@ static void __init vmware_platform_setup(void)
 
 		vmware_tsc_khz = tsc_khz;
 		x86_platform.calibrate_tsc = vmware_get_tsc_khz;
+		x86_platform.calibrate_cpu = vmware_get_tsc_khz;
 
 #ifdef CONFIG_X86_LOCAL_APIC
 		/* Skip lapic calibration since we know the bus frequency. */
-- 
2.10.1