Hi Tyler,
On 28/02/17 19:43, Baicar, Tyler wrote:
> On 2/24/2017 3:42 AM, James Morse wrote:
>> On 21/02/17 21:22, Tyler Baicar wrote:
>>> Currently external aborts are unsupported by the guest abort
>>> handling. Add handling for SEAs so that the host kernel reports
>>> SEAs which occur in the guest kernel.
>>> diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c
>>> index b2d57fc..403277b 100644
>>> --- a/arch/arm64/mm/fault.c
>>> +++ b/arch/arm64/mm/fault.c
>>> @@ -602,6 +602,24 @@ static const char *fault_name(unsigned int esr)
>>> }
>>>
>>> /*
>>> + * Handle Synchronous External Aborts that occur in a guest kernel.
>>> + */
>>> +int handle_guest_sea(unsigned long addr, unsigned int esr)
>>> +{
>>> + if(IS_ENABLED(HAVE_ACPI_APEI_SEA)) {
>>> + nmi_enter();
>>> + ghes_notify_sea();
>>> + nmi_exit();
>> This nmi stuff was needed for synchronous aborts that may have interrupted
>> APEI's interrupts-masked code. We want to avoid trying to take the same set of
>> locks, hence taking the in_nmi() path through APEI. Here we know we interrupted
>> a guest, so there is no risk that we have interrupted APEI on the host.
>> ghes_notify_sea() can safely take the normal path.
> Makes sense, I can remove the nmi_* calls here.
Just occurs to me: if we do this we need to add the rcu_read_lock() in
ghes_notify_sea() as its not protected by the rcu/nmi weirdness.
Thanks,
James
Hello James,
On 3/6/2017 3:28 AM, James Morse wrote:
> On 28/02/17 19:43, Baicar, Tyler wrote:
>> On 2/24/2017 3:42 AM, James Morse wrote:
>>> On 21/02/17 21:22, Tyler Baicar wrote:
>>>> Currently external aborts are unsupported by the guest abort
>>>> handling. Add handling for SEAs so that the host kernel reports
>>>> SEAs which occur in the guest kernel.
>>>> diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c
>>>> index b2d57fc..403277b 100644
>>>> --- a/arch/arm64/mm/fault.c
>>>> +++ b/arch/arm64/mm/fault.c
>>>> @@ -602,6 +602,24 @@ static const char *fault_name(unsigned int esr)
>>>> }
>>>>
>>>> /*
>>>> + * Handle Synchronous External Aborts that occur in a guest kernel.
>>>> + */
>>>> +int handle_guest_sea(unsigned long addr, unsigned int esr)
>>>> +{
>>>> + if(IS_ENABLED(HAVE_ACPI_APEI_SEA)) {
>>>> + nmi_enter();
>>>> + ghes_notify_sea();
>>>> + nmi_exit();
>>> This nmi stuff was needed for synchronous aborts that may have interrupted
>>> APEI's interrupts-masked code. We want to avoid trying to take the same set of
>>> locks, hence taking the in_nmi() path through APEI. Here we know we interrupted
>>> a guest, so there is no risk that we have interrupted APEI on the host.
>>> ghes_notify_sea() can safely take the normal path.
>> Makes sense, I can remove the nmi_* calls here.
> Just occurs to me: if we do this we need to add the rcu_read_lock() in
> ghes_notify_sea() as its not protected by the rcu/nmi weirdness.
>
True, would you suggest leaving these nmi_* calls or adding the rcu_*
calls? And since that's only needed for this KVM case, shouldn't the
rcu_* calls just replace the nmi_* calls here (outside of ghes_notify_sea)?
Thanks,
Tyler
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