[PATCH v11 4/6] target-arm: kvm64: detect guest RAS EXTENSION feature

On 8 September 2017 at 15:26, gengdongjiu [off-list ref] wrote:

quoted

Shouldn't we need to also tell the kernel that we actually want
it to expose RAS to the guest? Compare the PMU code in this function,
where we set a kvm_init_features bit to do this.

In the PMU code, it indeed sets a kvm_init_features bit. Here ARM
James has a concern that we are depend on the host CPU RAS extension,
He means that if userspace receives the SIGBUS delivered by host
memory_failure(), user space should record the CPER for guest
and handling the error regardless whether host CPU supports RAS
extension. But I think if user space receives the SIGBUS signal,
that means
host CPU RAS module detects the error or CPU consumes the poison
data, thus we should check whether physical CPU support RAS extension.

I don't understand what you have in mind here. If the host does
not support the CPU RAS extension then we should never get a
SIGBUS in the first place.

In any case this doesn't seem relevant to the question of whether it
should be optional to expose the RAS extension to the *guest*.
Even if the host does support RAS, you should be able to run a
VM that knows nothing about RAS.

thanks
-- PMM