On 09/05/18 17:11, Roger Pau Monné wrote: > On Wed, May 09, 2018 at 12:30:16PM +0100, Roger Pau Monné wrote: >> On Wed, May 09, 2018 at 11:56:40AM +0100, Andrew Cooper wrote: >>> On 09/05/18 11:21, Roger Pau Monne wrote: >>> I'm not sure that setting the default MTRR type is going to be a >>> clever idea in hindsight when we come to doing PCI Passthrough support. >> >> Setting the default type to WB is also set by hvmloader, it's just >> that hvmloader also sets some of the fixed and variable ranges to UC >> in order to cover the iomem areas. >> >> The expectations when doing pci-passthrough is that the guest will >> always use paging and PAT in order to set the appropriate cache >> attributes, or else the guest itself will have to program the UC MTRR >> ranges, I admit that's not very nice however. >> >> What about enabling the default MTRR type and setting it to WB in the >> toolstack for PVH? IMO doing it Xen itself would be wrong. > > I have the following patch to set the default MTRR type, but I think > if we go down this road then we will also have to set UC MTRRs for > MMIO areas, which again seems fine to me.
I like this route much better. Juergen > > ---8<--- > diff --git a/tools/libxc/xc_dom_x86.c b/tools/libxc/xc_dom_x86.c > index e33a28847d..3cb1a1720f 100644 > --- a/tools/libxc/xc_dom_x86.c > +++ b/tools/libxc/xc_dom_x86.c > @@ -938,6 +938,8 @@ static int vcpu_hvm(struct xc_dom_image *dom) > HVM_SAVE_TYPE(HEADER) header; > struct hvm_save_descriptor cpu_d; > HVM_SAVE_TYPE(CPU) cpu; > + struct hvm_save_descriptor mtrr_d; > + HVM_SAVE_TYPE(MTRR) mtrr; > struct hvm_save_descriptor end_d; > HVM_SAVE_TYPE(END) end; > } bsp_ctx; > @@ -1014,6 +1016,15 @@ static int vcpu_hvm(struct xc_dom_image *dom) > if ( dom->start_info_seg.pfn ) > bsp_ctx.cpu.rbx = dom->start_info_seg.pfn << PAGE_SHIFT; > > + /* Set the MTRR. */ > + bsp_ctx.mtrr_d.typecode = HVM_SAVE_CODE(MTRR); > + bsp_ctx.mtrr_d.instance = 0; > + bsp_ctx.mtrr_d.length = HVM_SAVE_LENGTH(MTRR); > + /* XXX: maybe this should be a firmware option instead? */ > + if ( !dom->device_model ) > + /* Enable MTRR (bit 11) and set the default type to WB (6). */ > + bsp_ctx.mtrr.msr_mtrr_def_type = (1u << 11) | 6; > + > /* Set the end descriptor. */ > bsp_ctx.end_d.typecode = HVM_SAVE_CODE(END); > bsp_ctx.end_d.instance = 0; > > _______________________________________________ Xen-devel mailing list Xen-devel@lists.xenproject.org https://lists.xenproject.org/mailman/listinfo/xen-devel
