On Tue, May 28, 2013 at 3:11 AM, Marc Zyngier <marc.zyngier@xxxxxxx> wrote: > On 27/05/13 21:01, Christoffer Dall wrote: >> On Tue, May 14, 2013 at 4:11 AM, Marc Zyngier <marc.zyngier@xxxxxxx> wrote: >>> At the moment, when mapping a device into Stage-2 for a guest, >>> we override whatever the guest uses by forcing a device memory >>> type in Stage-2. >>> >>> While this is not exactly wrong, this isn't really the "spirit" of >>> the architecture. The hardware shouldn't have to cope for a broken >>> guest mapping to a device as normal memory. >>> >> >> So I'm trying to think of a scenario where this feature in the >> architecture would actually be useful, and it sounds like from you >> guys that it's only useful to properly run a broken guest. >> >> Are we 100% sure that a malicious guest can't leverage this to break >> isolation? I'm thinking something along the lines of writing to a >> device (for example the gic virtual cpu interface) with a cached >> mapping. If such a write is in fact written back to cache, and not >> evicted from the cache before a later time, where a different VM is >> running, can't that adversely affect the other VM? >> >> Probably this can never happen, but I wasn't able to convince myself >> of this from going through the ARM ARM...? > > I think you definitely have a point here, and I completely missed that > case. A shared device (like the GIC virtual CPU interface) must be > forced to a device memory type, otherwise we cannot ensure strict > isolation of guests. > > I'll drop this patch from my series and add PAGE_S2_DEVICE back to the > arm64 port. > We still need to get rid of the USER bit in the definition, and since that's a purely arch/arm/* patch I assume it should go through RMK's tree. Will you ack the other patch? Thanks, -Christoffer -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
