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Tsirkin" To: Thomas Gleixner Cc: Jason Wang , virtualization , linux-kernel , "Hetzelt, Felicitas" , "kaplan, david" , Konrad Rzeszutek Wilk , pbonzini , Andi Kleen , Dan Williams , "Kuppuswamy, Sathyanarayanan" , Ingo Molnar , Borislav Petkov , Peter Zijlstra , Andy Lutomirski , Bjorn Helgaas , Richard Henderson , Thomas Bogendoerfer , James E J Bottomley , Helge Deller , "David S . Miller" , Arnd Bergmann , Jonathan Corbet , Peter H Anvin , Dave Hansen , Tony Luck , Kirill Shutemov , Sean Christopherson , Kuppuswamy Sathyanarayanan , X86 ML Subject: Re: [PATCH 6/9] virtio_pci: harden MSI-X interrupts Message-ID: <20210913164934-mutt-send-email-mst@kernel.org> References: <20210913055353.35219-1-jasowang@redhat.com> <20210913055353.35219-7-jasowang@redhat.com> <20210913015711-mutt-send-email-mst@kernel.org> <20210913022257-mutt-send-email-mst@kernel.org> <20210913023626-mutt-send-email-mst@kernel.org> <20210913024153-mutt-send-email-mst@kernel.org> <87bl4wfeq1.ffs@tglx> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87bl4wfeq1.ffs@tglx> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Sep 13, 2021 at 09:38:30PM +0200, Thomas Gleixner wrote: > On Mon, Sep 13 2021 at 15:07, Jason Wang wrote: > > On Mon, Sep 13, 2021 at 2:50 PM Michael S. Tsirkin wrote: > >> > But doen't "irq is disabled" basically mean "we told the hypervisor > >> > to disable the irq"? What extractly prevents hypervisor from > >> > sending the irq even if guest thinks it disabled it? > >> > >> More generally, can't we for example blow away the > >> indir_desc array that we use to keep the ctx pointers? > >> Won't that be enough? > > > > I'm not sure how it is related to the indirect descriptor but an > > example is that all the current driver will assume: > > > > 1) the interrupt won't be raised before virtio_device_ready() > > 2) the interrupt won't be raised after reset() > > If that assumption exists, then you better keep the interrupt line > disabled until virtio_device_ready() has completed started not completed. device is allowed to send config interrupts right after DRIVER_OK status is set by virtio_device_ready. > and disable it again > before reset() is invoked. That's a question of general robustness and > not really a question of trusted hypervisors and encrypted guests. We can do this for some MSIX interrupts, sure. Not for shared interrupts though. > >> > > > > > > +void vp_disable_vectors(struct virtio_device *vdev) > >> > > > > > > { > >> > > > > > > struct virtio_pci_device *vp_dev = to_vp_device(vdev); > >> > > > > > > int i; > >> > > > > > > @@ -34,7 +34,20 @@ void vp_synchronize_vectors(struct virtio_device *vdev) > >> > > > > > > synchronize_irq(vp_dev->pci_dev->irq); > > Don't you want the same change for non-MSI interrupts? We can't disable them - these are shared. > Thanks, > > tglx