On 21/06/2018 17:06, Radim Krčmář wrote:
>> Signed-off-by: Andreas Steinmetz <ast@xxxxxxxx>
>> ---
>> arch/x86/kernel/kvmclock.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/arch/x86/kernel/kvmclock.c b/arch/x86/kernel/kvmclock.c
>> index bf8d1eb7fca3..6aee5c6265b3 100644
>> --- a/arch/x86/kernel/kvmclock.c
>> +++ b/arch/x86/kernel/kvmclock.c
>> @@ -350,7 +350,7 @@ void __init kvmclock_init(void)
>>
>> int __init kvm_setup_vsyscall_timeinfo(void)
>> {
>> -#ifdef CONFIG_X86_64
>> +#ifdef CONFIG_X86_64 || defined(CONFIG_X86_32)
>
> The code should actually read "#if defined(...", or be omitted as we
> have only these two x86 variants. The correct variant might cause
> unexpected bugs by enabling the vsyscall on 32 bit kernels.
>
> Please check that the following patch fixes your problem as well,
>
> thanks.
Thanks Radim, I queued your patch.
Paolo
> ---8<---
> pvti_cpu0_va is the address of shared kvmclock data structure.
>
> pvti_cpu0_va is currently kept unset (1) on 32 bit systems, (2) when
> kvmclock vsyscall is disabled, and (3) if kvmclock is not stable.
> This poses a problem, because kvm_ptp needs pvti_cpu0_va, but (1) can
> work on 32 bit, (2) has little relation to the vsyscall, and (3) does
> not need stable kvmclock (although kvmclock won't be used for system
> clock if it's not stable, so kvm_ptp is pointless in that case).
>
> Expose pvti_cpu0_va whenever kvmclock is enabled to allow all users to
> work with it.
>
> This fixes a regression found on Gentoo: https://bugs.gentoo.org/658544.
>
> Fixes: 9f08890ab906 ("x86/pvclock: add setter for pvclock_pvti_cpu0_va")
> Reported-by: Andreas Steinmetz <ast@xxxxxxxx>
> Signed-off-by: Radim Krčmář <rkrcmar@xxxxxxxxxx>
> ---
> arch/x86/kernel/kvmclock.c | 11 +++++------
> 1 file changed, 5 insertions(+), 6 deletions(-)
>
> diff --git a/arch/x86/kernel/kvmclock.c b/arch/x86/kernel/kvmclock.c
> index bf8d1eb7fca3..46ffa8327563 100644
> --- a/arch/x86/kernel/kvmclock.c
> +++ b/arch/x86/kernel/kvmclock.c
> @@ -319,6 +319,8 @@ void __init kvmclock_init(void)
> printk(KERN_INFO "kvm-clock: Using msrs %x and %x",
> msr_kvm_system_time, msr_kvm_wall_clock);
>
> + pvclock_set_pvti_cpu0_va(hv_clock);
> +
> if (kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE_STABLE_BIT))
> pvclock_set_flags(PVCLOCK_TSC_STABLE_BIT);
>
> @@ -366,14 +368,11 @@ int __init kvm_setup_vsyscall_timeinfo(void)
> vcpu_time = &hv_clock[cpu].pvti;
> flags = pvclock_read_flags(vcpu_time);
>
> - if (!(flags & PVCLOCK_TSC_STABLE_BIT)) {
> - put_cpu();
> - return 1;
> - }
> -
> - pvclock_set_pvti_cpu0_va(hv_clock);
> put_cpu();
>
> + if (!(flags & PVCLOCK_TSC_STABLE_BIT))
> + return 1;
> +
> kvm_clock.archdata.vclock_mode = VCLOCK_PVCLOCK;
> #endif
> return 0;
>
