On Fri, Apr 17, 2020 at 12:57:16PM +0200, Jan Beulich wrote: > On 17.04.2020 12:26, Roger Pau Monne wrote: > > The EPT page tables can be shared with the IOMMU as long as the page > > sizes supported by EPT are also supported by the IOMMU. > > > > Current code checks that both the IOMMU and EPT support the same page > > sizes, but this is not strictly required, the IOMMU supporting more > > page sizes than EPT is fine and shouldn't block page sharing. > > Meaning the check isn't wrong, just too strict. Hence maybe > "relax" instead of "fix" in the subject? > > Also "... page table sharing."
Sure. > > --- a/xen/drivers/passthrough/vtd/iommu.c > > +++ b/xen/drivers/passthrough/vtd/iommu.c > > @@ -1914,8 +1914,10 @@ static int __init vtd_ept_page_compatible(struct > > vtd_iommu *iommu) > > if ( rdmsr_safe(MSR_IA32_VMX_EPT_VPID_CAP, ept_cap) != 0 ) > > return 0; > > > > - return (ept_has_2mb(ept_cap) && opt_hap_2mb) == cap_sps_2mb(vtd_cap) && > > - (ept_has_1gb(ept_cap) && opt_hap_1gb) == cap_sps_1gb(vtd_cap); > > + return ((ept_has_2mb(ept_cap) && opt_hap_2mb) ? cap_sps_2mb(vtd_cap) > > + : true) && > > + ((ept_has_1gb(ept_cap) && opt_hap_1gb) ? cap_sps_1gb(vtd_cap) > > + : true); > > I have to admit that I always find it odd to have "true" or "false" > as the 2nd or 3rd operand of a ternary. How about simply changing > == to <= in the original expression? I find it weird to use <= to compare booleans, but I can change it. Let me post a new version with the adjustments to the commit message and this requested change. Thanks, Roger.
