Messages in this thread | | | From | Paul Durrant <> | Date | Thu, 2 Nov 2023 18:01:35 +0000 | Subject | Re: [PATCH v7 05/11] KVM: pfncache: allow a cache to be activated with a fixed (userspace) HVA |
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On 31/10/2023 23:49, Sean Christopherson wrote: > On Mon, Oct 02, 2023, Paul Durrant wrote: >> diff --git a/include/linux/kvm_types.h b/include/linux/kvm_types.h >> index 6f4737d5046a..d49946ee7ae3 100644 >> --- a/include/linux/kvm_types.h >> +++ b/include/linux/kvm_types.h >> @@ -64,7 +64,7 @@ struct gfn_to_hva_cache { >> >> struct gfn_to_pfn_cache { >> u64 generation; >> - gpa_t gpa; >> + u64 addr; > > Holy moly, we have unions for exactly this reason. > > union { > gpa_t gpa; > unsigned long addr; > }; > > But that's also weird and silly because it's basically the exact same thing as > "uhva". If "uhva" stores the full address instead of the page-aligned address, > then I don't see a need for unionizing the gpa and uhva. >
Ok, I think that'll be more invasive but I'll see how it looks.
> kvm_xen_vcpu_get_attr() should darn well explicitly check that the gpc stores > the correct type and not bleed ABI into the gfn_to_pfn_cache implementation. >
I guess if we leave gpa alone and make it INVALID_GPA for caches initialized using an HVA then that can be checked. Is that what you mean here?
> If there's a true need for a union, the helpers should WARN. > >> +unsigned long kvm_gpc_hva(struct gfn_to_pfn_cache *gpc) >> +{ >> + return !gpc->addr_is_gpa ? gpc->addr : 0; > > '0' is a perfectly valid address. Yeah, practically speaking '0' can't be used > these days, but we already have KVM_HVA_ERR_BAD. If y'all want to use the for the > Xen ABI, then so be it. But the common helpers need to use a sane value.
Ok.
Paul
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