* [PATCH] KVM: kvmclock: Fix vCPUs > 64 can't be online/hotpluged
@ 2021-01-14 11:27 Wanpeng Li
2021-01-14 13:45 ` Vitaly Kuznetsov
0 siblings, 1 reply; 5+ messages in thread
From: Wanpeng Li @ 2021-01-14 11:27 UTC (permalink / raw)
To: linux-kernel, kvm
Cc: Paolo Bonzini, Sean Christopherson, Vitaly Kuznetsov, Wanpeng Li,
Jim Mattson, Joerg Roedel, Brijesh Singh
From: Wanpeng Li <wanpengli@tencent.com>
The per-cpu vsyscall pvclock data pointer assigns either an element of the
static array hv_clock_boot (#vCPU <= 64) or dynamically allocated memory
hvclock_mem (vCPU > 64), the dynamically memory will not be allocated if
kvmclock vsyscall is disabled, this can result in cpu hotpluged fails in
kvmclock_setup_percpu() which returns -ENOMEM. This patch fixes it by not
assigning vsyscall pvclock data pointer if kvmclock vdso_clock_mode is not
VDSO_CLOCKMODE_PVCLOCK.
Fixes: 6a1cac56f4 ("x86/kvm: Use __bss_decrypted attribute in shared variables")
Reported-by: Zelin Deng <zelin.deng@linux.alibaba.com>
Tested-by: Haiwei Li <lihaiwei@tencent.com>
Cc: Brijesh Singh <brijesh.singh@amd.com>
Cc: stable@vger.kernel.org#v4.19-rc5+
Signed-off-by: Wanpeng Li <wanpengli@tencent.com>
---
arch/x86/kernel/kvmclock.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/arch/x86/kernel/kvmclock.c b/arch/x86/kernel/kvmclock.c
index aa59374..0624290 100644
--- a/arch/x86/kernel/kvmclock.c
+++ b/arch/x86/kernel/kvmclock.c
@@ -296,7 +296,8 @@ static int kvmclock_setup_percpu(unsigned int cpu)
* pointers. So carefully check. CPU0 has been set up in init
* already.
*/
- if (!cpu || (p && p != per_cpu(hv_clock_per_cpu, 0)))
+ if (!cpu || (p && p != per_cpu(hv_clock_per_cpu, 0)) ||
+ (kvm_clock.vdso_clock_mode != VDSO_CLOCKMODE_PVCLOCK))
return 0;
/* Use the static page for the first CPUs, allocate otherwise */
--
2.7.4
^ permalink raw reply related [flat|nested] 5+ messages in thread
* Re: [PATCH] KVM: kvmclock: Fix vCPUs > 64 can't be online/hotpluged
2021-01-14 11:27 [PATCH] KVM: kvmclock: Fix vCPUs > 64 can't be online/hotpluged Wanpeng Li
@ 2021-01-14 13:45 ` Vitaly Kuznetsov
2021-01-15 1:15 ` Wanpeng Li
0 siblings, 1 reply; 5+ messages in thread
From: Vitaly Kuznetsov @ 2021-01-14 13:45 UTC (permalink / raw)
To: Wanpeng Li
Cc: Paolo Bonzini, Sean Christopherson, Wanpeng Li, Jim Mattson,
Joerg Roedel, Brijesh Singh, linux-kernel, kvm
Wanpeng Li <kernellwp@gmail.com> writes:
> From: Wanpeng Li <wanpengli@tencent.com>
>
> The per-cpu vsyscall pvclock data pointer assigns either an element of the
> static array hv_clock_boot (#vCPU <= 64) or dynamically allocated memory
> hvclock_mem (vCPU > 64), the dynamically memory will not be allocated if
> kvmclock vsyscall is disabled, this can result in cpu hotpluged fails in
> kvmclock_setup_percpu() which returns -ENOMEM. This patch fixes it by not
> assigning vsyscall pvclock data pointer if kvmclock vdso_clock_mode is not
> VDSO_CLOCKMODE_PVCLOCK.
>
> Fixes: 6a1cac56f4 ("x86/kvm: Use __bss_decrypted attribute in shared variables")
> Reported-by: Zelin Deng <zelin.deng@linux.alibaba.com>
> Tested-by: Haiwei Li <lihaiwei@tencent.com>
> Cc: Brijesh Singh <brijesh.singh@amd.com>
> Cc: stable@vger.kernel.org#v4.19-rc5+
> Signed-off-by: Wanpeng Li <wanpengli@tencent.com>
> ---
> arch/x86/kernel/kvmclock.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/arch/x86/kernel/kvmclock.c b/arch/x86/kernel/kvmclock.c
> index aa59374..0624290 100644
> --- a/arch/x86/kernel/kvmclock.c
> +++ b/arch/x86/kernel/kvmclock.c
> @@ -296,7 +296,8 @@ static int kvmclock_setup_percpu(unsigned int cpu)
> * pointers. So carefully check. CPU0 has been set up in init
> * already.
> */
> - if (!cpu || (p && p != per_cpu(hv_clock_per_cpu, 0)))
> + if (!cpu || (p && p != per_cpu(hv_clock_per_cpu, 0)) ||
> + (kvm_clock.vdso_clock_mode != VDSO_CLOCKMODE_PVCLOCK))
> return 0;
The comment above should probably be updated as it is not clear why we
check kvm_clock.vdso_clock_mode here. Actually, I would even suggest we
introduce a 'kvmclock_tsc_stable' global instead to avoid this indirect
check.
>
> /* Use the static page for the first CPUs, allocate otherwise */
Also, would it be better if we just avoid cpuhp_setup_state() call in
this case? E.g. both these ideas combined (completely untested):
diff --git a/arch/x86/kernel/kvmclock.c b/arch/x86/kernel/kvmclock.c
index aa593743acf6..0827aef3ccb8 100644
--- a/arch/x86/kernel/kvmclock.c
+++ b/arch/x86/kernel/kvmclock.c
@@ -25,6 +25,7 @@
static int kvmclock __initdata = 1;
static int kvmclock_vsyscall __initdata = 1;
+static bool kvmclock_tsc_stable __ro_after_init = true;
static int msr_kvm_system_time __ro_after_init = MSR_KVM_SYSTEM_TIME;
static int msr_kvm_wall_clock __ro_after_init = MSR_KVM_WALL_CLOCK;
static u64 kvm_sched_clock_offset __ro_after_init;
@@ -275,8 +276,10 @@ static int __init kvm_setup_vsyscall_timeinfo(void)
return 0;
flags = pvclock_read_flags(&hv_clock_boot[0].pvti);
- if (!(flags & PVCLOCK_TSC_STABLE_BIT))
+ if (!(flags & PVCLOCK_TSC_STABLE_BIT)) {
+ kvmclock_tsc_stable = false;
return 0;
+ }
kvm_clock.vdso_clock_mode = VDSO_CLOCKMODE_PVCLOCK;
#endif
@@ -325,7 +328,8 @@ void __init kvmclock_init(void)
return;
}
- if (cpuhp_setup_state(CPUHP_BP_PREPARE_DYN, "kvmclock:setup_percpu",
+ if (kvmclock_tsc_stable &&
+ cpuhp_setup_state(CPUHP_BP_PREPARE_DYN, "kvmclock:setup_percpu",
kvmclock_setup_percpu, NULL) < 0) {
return;
}
--
Vitaly
^ permalink raw reply related [flat|nested] 5+ messages in thread
* Re: [PATCH] KVM: kvmclock: Fix vCPUs > 64 can't be online/hotpluged
2021-01-14 13:45 ` Vitaly Kuznetsov
@ 2021-01-15 1:15 ` Wanpeng Li
2021-01-18 18:26 ` Paolo Bonzini
0 siblings, 1 reply; 5+ messages in thread
From: Wanpeng Li @ 2021-01-15 1:15 UTC (permalink / raw)
To: Vitaly Kuznetsov
Cc: Paolo Bonzini, Sean Christopherson, Wanpeng Li, Jim Mattson,
Joerg Roedel, Brijesh Singh, LKML, kvm
On Thu, 14 Jan 2021 at 21:45, Vitaly Kuznetsov <vkuznets@redhat.com> wrote:
>
> Wanpeng Li <kernellwp@gmail.com> writes:
>
> > From: Wanpeng Li <wanpengli@tencent.com>
> >
> > The per-cpu vsyscall pvclock data pointer assigns either an element of the
> > static array hv_clock_boot (#vCPU <= 64) or dynamically allocated memory
> > hvclock_mem (vCPU > 64), the dynamically memory will not be allocated if
> > kvmclock vsyscall is disabled, this can result in cpu hotpluged fails in
> > kvmclock_setup_percpu() which returns -ENOMEM. This patch fixes it by not
> > assigning vsyscall pvclock data pointer if kvmclock vdso_clock_mode is not
> > VDSO_CLOCKMODE_PVCLOCK.
> >
> > Fixes: 6a1cac56f4 ("x86/kvm: Use __bss_decrypted attribute in shared variables")
> > Reported-by: Zelin Deng <zelin.deng@linux.alibaba.com>
> > Tested-by: Haiwei Li <lihaiwei@tencent.com>
> > Cc: Brijesh Singh <brijesh.singh@amd.com>
> > Cc: stable@vger.kernel.org#v4.19-rc5+
> > Signed-off-by: Wanpeng Li <wanpengli@tencent.com>
> > ---
> > arch/x86/kernel/kvmclock.c | 3 ++-
> > 1 file changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/arch/x86/kernel/kvmclock.c b/arch/x86/kernel/kvmclock.c
> > index aa59374..0624290 100644
> > --- a/arch/x86/kernel/kvmclock.c
> > +++ b/arch/x86/kernel/kvmclock.c
> > @@ -296,7 +296,8 @@ static int kvmclock_setup_percpu(unsigned int cpu)
> > * pointers. So carefully check. CPU0 has been set up in init
> > * already.
> > */
> > - if (!cpu || (p && p != per_cpu(hv_clock_per_cpu, 0)))
> > + if (!cpu || (p && p != per_cpu(hv_clock_per_cpu, 0)) ||
> > + (kvm_clock.vdso_clock_mode != VDSO_CLOCKMODE_PVCLOCK))
> > return 0;
>
> The comment above should probably be updated as it is not clear why we
> check kvm_clock.vdso_clock_mode here. Actually, I would even suggest we
> introduce a 'kvmclock_tsc_stable' global instead to avoid this indirect
> check.
I prefer to update the comment above, assign vsyscall pvclock data
pointer iff kvmclock vsyscall is enabled.
Wanpeng
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] KVM: kvmclock: Fix vCPUs > 64 can't be online/hotpluged
2021-01-15 1:15 ` Wanpeng Li
@ 2021-01-18 18:26 ` Paolo Bonzini
2021-01-19 0:28 ` Wanpeng Li
0 siblings, 1 reply; 5+ messages in thread
From: Paolo Bonzini @ 2021-01-18 18:26 UTC (permalink / raw)
To: Wanpeng Li, Vitaly Kuznetsov
Cc: Sean Christopherson, Wanpeng Li, Jim Mattson, Joerg Roedel,
Brijesh Singh, LKML, kvm
On 15/01/21 02:15, Wanpeng Li wrote:
>> The comment above should probably be updated as it is not clear why we
>> check kvm_clock.vdso_clock_mode here. Actually, I would even suggest we
>> introduce a 'kvmclock_tsc_stable' global instead to avoid this indirect
>> check.
> I prefer to update the comment above, assign vsyscall pvclock data
> pointer iff kvmclock vsyscall is enabled.
Are you going to send v2?
Paolo
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] KVM: kvmclock: Fix vCPUs > 64 can't be online/hotpluged
2021-01-18 18:26 ` Paolo Bonzini
@ 2021-01-19 0:28 ` Wanpeng Li
0 siblings, 0 replies; 5+ messages in thread
From: Wanpeng Li @ 2021-01-19 0:28 UTC (permalink / raw)
To: Paolo Bonzini
Cc: Vitaly Kuznetsov, Sean Christopherson, Wanpeng Li, Jim Mattson,
Joerg Roedel, Brijesh Singh, LKML, kvm
On Tue, 19 Jan 2021 at 02:27, Paolo Bonzini <pbonzini@redhat.com> wrote:
>
> On 15/01/21 02:15, Wanpeng Li wrote:
> >> The comment above should probably be updated as it is not clear why we
> >> check kvm_clock.vdso_clock_mode here. Actually, I would even suggest we
> >> introduce a 'kvmclock_tsc_stable' global instead to avoid this indirect
> >> check.
> > I prefer to update the comment above, assign vsyscall pvclock data
> > pointer iff kvmclock vsyscall is enabled.
>
> Are you going to send v2?
Yes. :) https://lore.kernel.org/kvm/1610960877-3110-1-git-send-email-wanpengli@tencent.com/
Wanpeng
^ permalink raw reply [flat|nested] 5+ messages in thread
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2021-01-14 11:27 [PATCH] KVM: kvmclock: Fix vCPUs > 64 can't be online/hotpluged Wanpeng Li
2021-01-14 13:45 ` Vitaly Kuznetsov
2021-01-15 1:15 ` Wanpeng Li
2021-01-18 18:26 ` Paolo Bonzini
2021-01-19 0:28 ` Wanpeng Li
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