Messages in this thread |  | | Date | Tue, 18 May 2021 18:17:04 +0000 | | From | Sean Christopherson <> | | Subject | Re: [RFC v2-fix 1/1] x86/tdx: Handle in-kernel MMIO |
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On Tue, May 18, 2021, Andi Kleen wrote: > > Why does this code exist at all? TDX and SEV-ES absolutely must share code for > > handling MMIO reflection. It will require a fair amount of refactoring to move > > the guts of vc_handle_mmio() to common code, but there is zero reason to maintain > > two separate versions of the opcode cracking. > > While that's true on the high level, all the low level details are > different. We looked at unifying at some point, but it would have been a > callback hell. I don't think unifying would make anything cleaner.
How hard did you look? The only part that _must_ be different between SEV and TDX is the hypercall itself, which is wholly contained at the very end of vc_do_mmio().
Despite vc_slow_virt_to_phys() taking a pointer to the ghcb, it's unused and thus the function is 100% generic.
The ghcb->shared_buffer usage throughout the upper levels can be eliminated by refactoring the stack to take a "u64 *val", since MMIO accesses are currently bounded to 8 bytes.
> Besides the bulk of the decoding work is already unified in the common x86 > instruction decoder. The actual actions are different, and the code fetching > is also different
Huh? What do you mean by "actual actions"? Why is the code fetch different?
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