Re: [Xen-devel] [PATCH 15/18] xen/arm: Introduce a helper to synchronize SError
Hi Stefano,
On 2017/3/21 5:44, Stefano Stabellini wrote:
> On Mon, 20 Mar 2017, Stefano Stabellini wrote:
>> On Mon, 13 Mar 2017, Wei Chen wrote:
>>> We may have to isolate the SError between the context switch of
>>> 2 vCPUs or may have to prevent slipping hypervisor SError to guest.
>>
>> I thought the problem is not the risk of slipping hypervisor SErrors to
>> guest, but the risk of slipping previous guest SErrors to the next
>> guest. Is that right?
>
> I can see from the following patches that both situations are a risk.
> Although the patch could benefit from a better commit description:
>
> Reviewed-by: Stefano Stabellini
>
>
Thanks, I will update the commit message in next version.
>
>>> So we need a helper to synchronize SError before context switching
>>> or returning to guest.
>>>
>>> This function will be used by the later patches in this series, we
>>> use "#if 0" to disable it temporarily to remove compiler warnning.
>>>
>>> Signed-off-by: Wei Chen
>>> ---
>>> xen/arch/arm/traps.c | 11 +++
>>> 1 file changed, 11 insertions(+)
>>>
>>> diff --git a/xen/arch/arm/traps.c b/xen/arch/arm/traps.c
>>> index 44a0281..ee7865b 100644
>>> --- a/xen/arch/arm/traps.c
>>> +++ b/xen/arch/arm/traps.c
>>> @@ -2899,6 +2899,17 @@ asmlinkage void do_trap_hypervisor(struct
>>> cpu_user_regs *regs)
>>> }
>>> }
>>>
>>> +#if 0
>>> +static void synchronize_serror(void)
>>> +{
>>> +/* Synchronize against in-flight ld/st. */
>>> +dsb(sy);
>>> +
>>> +/* A single instruction exception window */
>>> +isb();
>>> +}
>>> +#endif
>>> +
>>> asmlinkage void do_trap_hyp_serror(struct cpu_user_regs *regs)
>>> {
>>> enter_hypervisor_head(regs);
>>> --
>>> 2.7.4
>>>
>>>
>>> ___
>>> Xen-devel mailing list
>>> Xen-devel@lists.xen.org
>>> https://lists.xen.org/xen-devel
>>>
>>
>
--
Regards,
Wei Chen
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Re: [Xen-devel] [PATCH 15/18] xen/arm: Introduce a helper to synchronize SError
On Mon, 20 Mar 2017, Stefano Stabellini wrote:
> On Mon, 13 Mar 2017, Wei Chen wrote:
> > We may have to isolate the SError between the context switch of
> > 2 vCPUs or may have to prevent slipping hypervisor SError to guest.
>
> I thought the problem is not the risk of slipping hypervisor SErrors to
> guest, but the risk of slipping previous guest SErrors to the next
> guest. Is that right?
I can see from the following patches that both situations are a risk.
Although the patch could benefit from a better commit description:
Reviewed-by: Stefano Stabellini
> > So we need a helper to synchronize SError before context switching
> > or returning to guest.
> >
> > This function will be used by the later patches in this series, we
> > use "#if 0" to disable it temporarily to remove compiler warnning.
> >
> > Signed-off-by: Wei Chen
> > ---
> > xen/arch/arm/traps.c | 11 +++
> > 1 file changed, 11 insertions(+)
> >
> > diff --git a/xen/arch/arm/traps.c b/xen/arch/arm/traps.c
> > index 44a0281..ee7865b 100644
> > --- a/xen/arch/arm/traps.c
> > +++ b/xen/arch/arm/traps.c
> > @@ -2899,6 +2899,17 @@ asmlinkage void do_trap_hypervisor(struct
> > cpu_user_regs *regs)
> > }
> > }
> >
> > +#if 0
> > +static void synchronize_serror(void)
> > +{
> > +/* Synchronize against in-flight ld/st. */
> > +dsb(sy);
> > +
> > +/* A single instruction exception window */
> > +isb();
> > +}
> > +#endif
> > +
> > asmlinkage void do_trap_hyp_serror(struct cpu_user_regs *regs)
> > {
> > enter_hypervisor_head(regs);
> > --
> > 2.7.4
> >
> >
> > ___
> > Xen-devel mailing list
> > Xen-devel@lists.xen.org
> > https://lists.xen.org/xen-devel
> >
>
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Re: [Xen-devel] [PATCH 15/18] xen/arm: Introduce a helper to synchronize SError
On Mon, 13 Mar 2017, Wei Chen wrote:
> We may have to isolate the SError between the context switch of
> 2 vCPUs or may have to prevent slipping hypervisor SError to guest.
I thought the problem is not the risk of slipping hypervisor SErrors to
guest, but the risk of slipping previous guest SErrors to the next
guest. Is that right?
> So we need a helper to synchronize SError before context switching
> or returning to guest.
>
> This function will be used by the later patches in this series, we
> use "#if 0" to disable it temporarily to remove compiler warnning.
>
> Signed-off-by: Wei Chen
> ---
> xen/arch/arm/traps.c | 11 +++
> 1 file changed, 11 insertions(+)
>
> diff --git a/xen/arch/arm/traps.c b/xen/arch/arm/traps.c
> index 44a0281..ee7865b 100644
> --- a/xen/arch/arm/traps.c
> +++ b/xen/arch/arm/traps.c
> @@ -2899,6 +2899,17 @@ asmlinkage void do_trap_hypervisor(struct
> cpu_user_regs *regs)
> }
> }
>
> +#if 0
> +static void synchronize_serror(void)
> +{
> +/* Synchronize against in-flight ld/st. */
> +dsb(sy);
> +
> +/* A single instruction exception window */
> +isb();
> +}
> +#endif
> +
> asmlinkage void do_trap_hyp_serror(struct cpu_user_regs *regs)
> {
> enter_hypervisor_head(regs);
> --
> 2.7.4
>
>
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>
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[Xen-devel] [PATCH 15/18] xen/arm: Introduce a helper to synchronize SError
We may have to isolate the SError between the context switch of
2 vCPUs or may have to prevent slipping hypervisor SError to guest.
So we need a helper to synchronize SError before context switching
or returning to guest.
This function will be used by the later patches in this series, we
use "#if 0" to disable it temporarily to remove compiler warnning.
Signed-off-by: Wei Chen
---
xen/arch/arm/traps.c | 11 +++
1 file changed, 11 insertions(+)
diff --git a/xen/arch/arm/traps.c b/xen/arch/arm/traps.c
index 44a0281..ee7865b 100644
--- a/xen/arch/arm/traps.c
+++ b/xen/arch/arm/traps.c
@@ -2899,6 +2899,17 @@ asmlinkage void do_trap_hypervisor(struct cpu_user_regs
*regs)
}
}
+#if 0
+static void synchronize_serror(void)
+{
+/* Synchronize against in-flight ld/st. */
+dsb(sy);
+
+/* A single instruction exception window */
+isb();
+}
+#endif
+
asmlinkage void do_trap_hyp_serror(struct cpu_user_regs *regs)
{
enter_hypervisor_head(regs);
--
2.7.4
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