Date: Tue, 6 Oct 2020 09:12:00 -0700 From: Sean Christopherson Message-ID: <20201006161200.GB17610@linux.intel.com> References: <20201002200214.GB10232@redhat.com> <20201002211314.GE24460@linux.intel.com> <20201005153318.GA4302@redhat.com> <20201005161620.GC11938@linux.intel.com> <20201006134629.GB5306@redhat.com> <877ds38n6r.fsf@vitty.brq.redhat.com> <20201006141501.GC5306@redhat.com> <874kn78l2z.fsf@vitty.brq.redhat.com> <20201006150817.GD5306@redhat.com> <871rib8ji1.fsf@vitty.brq.redhat.com> MIME-Version: 1.0 In-Reply-To: <871rib8ji1.fsf@vitty.brq.redhat.com> Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Subject: Re: [Virtio-fs] [PATCH v4] kvm, x86: Exit to user space in case page fault error List-Id: Development discussions about virtio-fs List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Vitaly Kuznetsov Cc: virtio-fs-list , pbonzini@redhat.com, kvm@vger.kernel.org, Vivek Goyal , linux-kernel@vger.kernel.org On Tue, Oct 06, 2020 at 05:24:54PM +0200, Vitaly Kuznetsov wrote: > Vivek Goyal writes: > > So you will have to report token (along with -EFAULT) to user space. So this > > is basically the 3rd proposal which is extension of kvm API and will > > report say HVA/GFN also to user space along with -EFAULT. > > Right, I meant to say that guest kernel has full register state of the > userspace process which caused APF to get queued and instead of trying > to extract it in KVM and pass to userspace in case of a (later) failure > we limit KVM api change to contain token or GFN only and somehow keep > the rest in the guest. This should help with TDX/SEV-ES. Whatever gets reported to userspace should be identical with and without async page faults, i.e. it definitely shouldn't have token information. Note, TDX doesn't allow injection exceptions, so reflecting a #PF back into the guest is not an option. Nor do I think that's "correct" behavior (see everyone's objections to using #PF for APF fixed). I.e. the event should probably be an IRQ.