Messages in this thread | | | Date | Wed, 12 May 2021 15:07:32 +0300 | From | "Kirill A. Shutemov" <> | Subject | Re: [RFC v2 01/32] x86/paravirt: Introduce CONFIG_PARAVIRT_XL |
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On Mon, May 10, 2021 at 05:56:05PM +0200, Juergen Gross wrote: > On 10.05.21 17:52, Andi Kleen wrote: > > \ > > > > > CONFIG_PARAVIRT_XL will be used by TDX that needs couple of paravirt > > > > > calls that were hidden under CONFIG_PARAVIRT_XXL, but the rest of the > > > > > config would be a bloat for TDX. > > > > > > > > Used how? Why is it bloat for TDX? > > > > > > Is there any major downside to move the halt related pvops functions > > > from CONFIG_PARAVIRT_XXL to CONFIG_PARAVIRT? > > > > I think the main motivation is to get rid of all the page table related > > hooks for modern configurations. These are the bulk of the annotations > > and cause bloat and worse code. Shadow page tables are really obscure > > these days and very few people still need them and it's totally > > reasonable to build even widely used distribution kernels without them. > > On contrast most of the other hooks are comparatively few and also on > > comparatively slow paths, so don't really matter too much. > > > > I think it would be ok to have a CONFIG_PARAVIRT that does not have page > > table support, and a separate config option for those (that could be > > eventually deprecated). > > > > But that would break existing .configs for those shadow stack users, > > that's why I think Kirill did it the other way around. > > No. We have PARAVIRT_XXL for Xen PV guests, and we have PARAVIRT for > other hypervisor's guests, supporting basically the TLB flush operations > and time related operations only. Adding the halt related operations to > PARAVIRT wouldn't break anything.
Yeah, I think we can do this. It should be fine.
-- Kirill A. Shutemov
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