> -----Original Message----- > From: Alex Williamson [mailto:alex.williamson@xxxxxxxxxx] > Sent: Saturday, December 07, 2013 1:00 AM > To: Wood Scott-B07421 > Cc: Bhushan Bharat-R65777; linux-pci@xxxxxxxxxxxxxxx; agraf@xxxxxxx; Yoder > Stuart-B08248; iommu@xxxxxxxxxxxxxxxxxxxxxxxxxx; bhelgaas@xxxxxxxxxx; linuxppc- > dev@xxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx > Subject: Re: [PATCH 0/9 v2] vfio-pci: add support for Freescale IOMMU (PAMU) > > On Fri, 2013-12-06 at 12:59 -0600, Scott Wood wrote: > > On Thu, 2013-12-05 at 22:11 -0600, Bharat Bhushan wrote: > > > > > > > -----Original Message----- > > > > From: Wood Scott-B07421 > > > > Sent: Friday, December 06, 2013 5:52 AM > > > > To: Bhushan Bharat-R65777 > > > > Cc: Alex Williamson; linux-pci@xxxxxxxxxxxxxxx; agraf@xxxxxxx; > > > > Yoder Stuart- B08248; iommu@xxxxxxxxxxxxxxxxxxxxxxxxxx; > > > > bhelgaas@xxxxxxxxxx; linuxppc- dev@xxxxxxxxxxxxxxxx; > > > > linux-kernel@xxxxxxxxxxxxxxx > > > > Subject: Re: [PATCH 0/9 v2] vfio-pci: add support for Freescale > > > > IOMMU (PAMU) > > > > > > > > On Thu, 2013-11-28 at 03:19 -0600, Bharat Bhushan wrote: > > > > > > > > > > > -----Original Message----- > > > > > > From: Bhushan Bharat-R65777 > > > > > > Sent: Wednesday, November 27, 2013 9:39 PM > > > > > > To: 'Alex Williamson' > > > > > > Cc: Wood Scott-B07421; linux-pci@xxxxxxxxxxxxxxx; > > > > > > agraf@xxxxxxx; Yoder Stuart- B08248; > > > > > > iommu@xxxxxxxxxxxxxxxxxxxxxxxxxx; bhelgaas@xxxxxxxxxx; > > > > > > linuxppc- dev@xxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx > > > > > > Subject: RE: [PATCH 0/9 v2] vfio-pci: add support for > > > > > > Freescale IOMMU (PAMU) > > > > > > > > > > > > If we just provide the size of MSI bank to userspace then > > > > > > userspace cannot do anything wrong. > > > > > > > > > > So userspace does not know address, so it cannot mmap and cause > > > > > any > > > > interference by directly reading/writing. > > > > > > > > That's security through obscurity... Couldn't the malicious user > > > > find out the address via other means, such as experimentation on > > > > another system over which they have full control? What would > > > > happen if the user reads from their device's PCI config space? Or > > > > gets the information via some back door in the PCI device they > > > > own? Or pokes throughout the address space looking for something that > generates an interrupt to its own device? > > > > > > So how to solve this problem, Any suggestion ? > > > > > > We have to map one window in PAMU for MSIs and a malicious user can > > > ask its device to do DMA to MSI window region with any pair of > > > address and data, which can lead to unexpected MSIs in system? > > > > I don't think there are any solutions other than to limit each bank to > > one user, unless the admin turns some knob that says they're OK with > > the partial loss of isolation. > > Even if the admin does opt-in to an allow_unsafe_interrupts options, it should > still be reasonably difficult for one guest to interfere with the other. I > don't think we want to rely on the blind luck of making the full MSI bank > accessible to multiple guests and hoping they don't step on each other. Not sure how to solve in this case (sharing MSI page) > That probably means that vfio needs to manage the space rather than the guest. What you mean by " vfio needs to manage the space rather than the guest"? Thanks -Bharat > Thanks, > > Alex > ��.n��������+%������w��{.n�����{���"�)�� jg��� �����ݢj����G���� ���j:+v���w�m������w�������h�����٥
