Hi Eric, Ricardo, On 9/10/21 20:32, Ricardo Koller wrote: > Hi Alexandru and Eric, > > On Fri, Sep 10, 2021 at 10:42:23AM +0200, Eric Auger wrote: >> Hi Alexandru, >> >> On 9/10/21 10:28 AM, Alexandru Elisei wrote: >>> Hi Ricardo, >>> >>> On 9/9/21 5:47 PM, Ricardo Koller wrote: >>>> On Thu, Sep 09, 2021 at 11:20:15AM +0100, Alexandru Elisei wrote: >>>>> Hi Ricardo, >>>>> >>>>> On 9/8/21 10:03 PM, Ricardo Koller wrote: >>>>>> Extend vgic_v3_check_base() to verify that the redistributor regions >>>>>> don't go above the VM-specified IPA size (phys_size). This can happen >>>>>> when using the legacy KVM_VGIC_V3_ADDR_TYPE_REDIST attribute with: >>>>>> >>>>>> base + size > phys_size AND base < phys_size >>>>>> >>>>>> vgic_v3_check_base() is used to check the redist regions bases when >>>>>> setting them (with the vcpus added so far) and when attempting the first >>>>>> vcpu-run. >>>>>> >>>>>> Signed-off-by: Ricardo Koller <ricarkol@xxxxxxxxxx> >>>>>> --- >>>>>> arch/arm64/kvm/vgic/vgic-v3.c | 4 ++++ >>>>>> 1 file changed, 4 insertions(+) >>>>>> >>>>>> diff --git a/arch/arm64/kvm/vgic/vgic-v3.c b/arch/arm64/kvm/vgic/vgic-v3.c >>>>>> index 66004f61cd83..5afd9f6f68f6 100644 >>>>>> --- a/arch/arm64/kvm/vgic/vgic-v3.c >>>>>> +++ b/arch/arm64/kvm/vgic/vgic-v3.c >>>>>> @@ -512,6 +512,10 @@ bool vgic_v3_check_base(struct kvm *kvm) >>>>>> if (rdreg->base + vgic_v3_rd_region_size(kvm, rdreg) < >>>>>> rdreg->base) >>>>>> return false; >>>>>> + >>>>>> + if (rdreg->base + vgic_v3_rd_region_size(kvm, rdreg) > >>>>>> + kvm_phys_size(kvm)) >>>>>> + return false; >>>>> Looks to me like this same check (and the overflow one before it) is done when >>>>> adding a new Redistributor region in kvm_vgic_addr() -> vgic_v3_set_redist_base() >>>>> -> vgic_v3_alloc_redist_region() -> vgic_check_ioaddr(). As far as I can tell, >>>>> kvm_vgic_addr() handles both ways of setting the Redistributor address. >>>>> >>>>> Without this patch, did you manage to set a base address such that base + size > >>>>> kvm_phys_size()? >>>>> >>>> Yes, with the KVM_VGIC_V3_ADDR_TYPE_REDIST legacy API. The easiest way >>>> to get to this situation is with the selftest in patch 2. I then tried >>>> an extra experiment: map the first redistributor, run the first vcpu, >>>> and access the redist from inside the guest. KVM didn't complain in any >>>> of these steps. >>> Yes, Eric pointed out that I was mistaken and there is no check being done for >>> base + size > kvm_phys_size(). >>> >>> What I was trying to say is that this check is better done when the user creates a >>> Redistributor region, not when a VCPU is first run. We have everything we need to >>> make the check when a region is created, why wait until the VCPU is run? >>> >>> For example, vgic_v3_insert_redist_region() is called each time the adds a new >>> Redistributor region (via either of the two APIs), and already has a check for the >>> upper limit overflowing (identical to the check in vgic_v3_check_base()). I would >>> add the check against the maximum IPA size there. >> you seem to refer to an old kernel as vgic_v3_insert_redist_region was >> renamed into� vgic_v3_alloc_redist_region in >> e5a35635464b kvm: arm64: vgic-v3: Introduce vgic_v3_free_redist_region() >> >> I think in case you use the old rdist API you do not know yet the size >> of the redist region at this point (count=0), hence Ricardo's choice to >> do the check latter. > Just wanted to add one more detail. vgic_v3_check_base() is also called > when creating the redistributor region (via vgic_v3_set_redist_base -> > vgic_register_redist_iodev). This patch reuses that check for the old > redist API to also check for "base + size > kvm_phys_size()" with a size > calculated using the vcpus added so far. @Eric: Indeed I was looking at an older kernel by mistake, thank you for pointing that out! Thank you both for the explanations, the piece I was missing was the fact that KVM_VGIC_V3_ADDR_TYPE_REDIST specifies only the base address and the limit for the region is the number of VCPUs * (KVM_VGIC_V3_REDIST_SIZE = 128K), which makes it necessary to have the check when each VCPU is first run (as far as I can tell, VCPUs can be created at any time). > >>> Also, because vgic_v3_insert_redist_region() already checks for overflow, I >>> believe the overflow check in vgic_v3_check_base() is redundant. >>> > It's redundant for the new redist API, but still needed for the old > redist API. Indeed. > >>> As far as I can tell, vgic_v3_check_base() is there to make sure that the >>> Distributor doesn't overlap with any of the Redistributors, and because the >>> Redistributors and the Distributor can be created in any order, we defer the check >>> until the first VCPU is run. I might be wrong about this, someone please correct >>> me if I'm wrong. >>> >>> Also, did you verify that KVM is also doing this check for GICv2? KVM does >>> something similar and calls vgic_v2_check_base() when mapping the GIC resources, >>> and I don't see a check for the maximum IPA size in that function either. >> I think vgic_check_ioaddr() called in kvm_vgic_addr() does the job (it >> checks the base @) >> > It seems that GICv2 suffers from the same problem. The cpu interface > base is checked but the end can extend above IPA size. Note that the cpu > interface is 8KBs and vgic_check_ioaddr() is only checking that its base ... except that the doc for KVM_VGIC_V2_ADDR_TYPE_CPU says that the CPU interface region is 4K, while the check in vgic_v2_check_base() is done against KVM_VGIC_V2_CPU_SIZE, which is 8K. I suppose that the CPU interface region is 8K because ARM IHI 0048B.b strongly recommends that the virtual CPU interface control registers are in a separate 4KB region, and KVM wants to emulate a GICv2 as close to the real thing as possible? > is 4KB aligned and below IPA size. The distributor region is 4KB so > vgic_check_ioaddr() is enough in that case. > > What about the following? > > I can work on the next version of this patch (v2 has the GICv2 issue) > which adds vgic_check_range(), which is like vgic_check_ioaddr() but > with a size arg. kvm_vgic_addr() can then call vgic_check_range() and > do all the checks for GICv2 and GICv3. Note that for GICv2, there's no > need to wait until first vcpu run to do the check. Also note that I will > have to keep the change in vgic_v3_check_base() to check for the old v3 > redist API at first vcpu run. Sounds good. Thanks, Alex > > Thanks, > Ricardo > >> Thanks >> >> Eric >>> Thanks, >>> >>> Alex >>> >>>> Thanks, >>>> Ricardo >>>> >>>>> Thanks, >>>>> >>>>> Alex >>>>> >>>>>> } >>>>>> >>>>>> if (IS_VGIC_ADDR_UNDEF(d->vgic_dist_base)) _______________________________________________ kvmarm mailing list kvmarm@xxxxxxxxxxxxxxxxxxxxx https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
