Hi Peter, On 9/14/23 16:57, Peter Maydell wrote: > The SMMUv3.1-XNX feature is mandatory for an SMMUv3.1 if S2P is > supported, so we should theoretically have implemented it as part of > the recent S2P work. Fortunately, for us the implementation is a > no-op. > > This feature is about interpretation of the stage 2 page table > descriptor XN bits, which control execute permissions. > > For QEMU, the permission bits passed to an IOMMU (via MemTxAttrs and > IOMMUAccessFlags) only indicate read and write; we do not distinguish > data reads from instruction reads outside the CPU proper. In the > SMMU architecture's terms, our interconnect between the client device > and the SMMU doesn't have the ability to convey the INST attribute, > and we therefore use the default value of "data" for this attribute. > > We also do not support the bits in the Stream Table Entry that can > override the on-the-bus transaction attribute permissions (we do not > set SMMU_IDR1.ATTR_PERMS_OVR=1). you may precise it is called INSTCFG > > These two things together mean that for our implementation, it never > has to deal with transactions with the INST attribute, and so it can > correctly ignore the XN bits entirely. So we already implement > FEAT_XNX's "XN field is now 2 bits, not 1" behaviour to the extent > that we need to. > > Advertise the presence of the feature in SMMU_IDR3.XNX. > > Signed-off-by: Peter Maydell <peter.mayd...@linaro.org> > --- > hw/arm/smmuv3.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/hw/arm/smmuv3.c b/hw/arm/smmuv3.c > index 94d388fc950..d9e639f7c41 100644 > --- a/hw/arm/smmuv3.c > +++ b/hw/arm/smmuv3.c > @@ -279,6 +279,7 @@ static void smmuv3_init_regs(SMMUv3State *s) > s->idr[1] = FIELD_DP32(s->idr[1], IDR1, CMDQS, SMMU_CMDQS); > > s->idr[3] = FIELD_DP32(s->idr[3], IDR3, HAD, 1); > + s->idr[3] = FIELD_DP32(s->idr[3], IDR3, XNX, 1); > s->idr[3] = FIELD_DP32(s->idr[3], IDR3, RIL, 1); > s->idr[3] = FIELD_DP32(s->idr[3], IDR3, BBML, 2); > With Mostafa's suggestion Reviewed-by: Eric Auger <eric.au...@redhat.com>
Thanks Eric
