RE: [Xen-devel] [PATCH] fix the time issue on x86_64

["Ian Pratt" <m+Ian.Pratt@xxxxxxxxxxxx>]

 > For x86_64, we must have a RTC driver compiled in kernel.
> I compiled a native x86_64 Linux kernel without any RTC 
> driver support, and the native Linux kernel also has the same 
> time issue.
> If we run hwclock, we get
>       Cannot access the Hardware Clock via any known method.
>       Use the --debug option to see the details of our search 
> for an access method.
> If this command fails, /etc/rc.d/rc.sysinit can not set 
> kernel time (by calling syscall settimeofday()) correctly.
> 
> And after adding CONFIG_RTC to xeno64 default config file, 
> the time issue is gone.
> But for i386, this is not a must, for it has some other way 
> to get the RTC time.

This will only work for privileged guests -- unprivileged guests can not
and should not be able to access the RTC directly.

The options are to either have our own /dev/rtc driver, or to emulate
reading the rtc in Xen for unprivilged guests (which is dead easy).

Ian

 
> Following is the patch:
> 
> # This is a BitKeeper generated diff -Nru style patch.
> #
> # ChangeSet
> #   2005/06/08 23:59:01-07:00 xin@xxxxxxxxxxxxxxxxxxxxxx
> #   fix time issue bug on x86_64
> #   Signed-off-by: Li B Xin <li.b.xin@xxxxxxxxx>
> #   Signed-off-by: Jun Nakajima <jun.nakajima@xxxxxxxxx>
> #
> # linux-2.6.11-xen-sparse/arch/xen/configs/xen0_defconfig_x86_64
> #   2005/06/08 23:59:00-07:00 xin@xxxxxxxxxxxxxxxxxxxxxx +1 -1
> #   fix time issue bug by adding RTC driver support.
> #   x86_64 must have a RTC driver support, or we can not run hwclock
> successfully, so we can not set a correct time to kernel.
> #   Signed-off-by: Li B Xin <li.b.xin@xxxxxxxxx>
> #   Signed-off-by: Jun Nakajima <jun.nakajima@xxxxxxxxx>
> #
> diff -Nru
> a/linux-2.6.11-xen-sparse/arch/xen/configs/xen0_defconfig_x86_64
> b/linux-2.6.11-xen-sparse/arch/xen/configs/xen0_defconfig_x86_64
> --- a/linux-2.6.11-xen-sparse/arch/xen/configs/xen0_defconfig_x86_64
> 2005-06-09 00:02:32 -07:00
> +++ b/linux-2.6.11-xen-sparse/arch/xen/configs/xen0_defconfig_x86_64
> 2005-06-09 00:02:32 -07:00
> @@ -701,7 +701,7 @@
>  # CONFIG_WATCHDOG is not set
>  # CONFIG_HW_RANDOM is not set
>  # CONFIG_NVRAM is not set
> -# CONFIG_RTC is not set
> +CONFIG_RTC=y
>  # CONFIG_GEN_RTC is not set
>  # CONFIG_DTLK is not set
>  # CONFIG_R3964 is not set
> 
> 
> thanks
> -Xin
> 
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> 

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