Am 13.01.22 um 13:30 schrieb David Woodhouse:
On Thu, 2022-01-13 at 13:14 +0100, Paolo Bonzini wrote:
On 1/13/22 13:06, Christian Borntraeger wrote:
From: Christian Borntraeger<
borntraeger@xxxxxxxxxx
Quick heads-up.
The new warnon triggers on s390. Here we write to the guest from an
irqfd worker. Since we do not use dirty_ring yet this might be an
over-indication.
Still have to look into that.
Yes, it's okay to add an #ifdef around the warning.
That would be #ifndef CONFIG_HAVE_KVM_DIRTY_RING, yes?
I already found it hard to write down the rules around how
kvm_vcpu_write_guest() doesn't use the vCPU it's passed, and how both
it and kvm_write_guest() need to be invoked on a pCPU which currently
owns *a* vCPU belonging to the same KVM... if we add "unless you're on
an architecture that doesn't support dirty ring logging", you may have
to pass me a bucket.
Are you proposing that as an officially documented part of the already
horrid API, or a temporary measure :)
Btw, that get_map_page() in arch/s390/kvm/interrupt.c looks like it has
the same use-after-free problem that kvm_map_gfn() used to have. It
probably wants converting to the new gfn_to_pfn_cache.
Take a look at how I resolve the same issue for delivering Xen event
channel interrupts.
Do you have a commit ID for your Xen event channel fix?
Although I gave myself a free pass on the dirty marking in that case,
by declaring that the shinfo page doesn't get marked dirty; it should
be considered *always* dirty. You might have less fun declaring that
retrospectively in your case.
