On Wed, Jun 28, 2023 at 10:38:23PM +0200, Peter Zijlstra wrote: > On Wed, Jun 28, 2023 at 05:29:01PM +0200, Peter Zijlstra wrote: > > On Tue, Jun 27, 2023 at 02:12:50AM +1200, Kai Huang wrote: > > > diff --git a/arch/x86/virt/vmx/tdx/tdxcall.S b/arch/x86/virt/vmx/tdx/tdxcall.S > > > index 49a54356ae99..757b0c34be10 100644 > > > --- a/arch/x86/virt/vmx/tdx/tdxcall.S > > > +++ b/arch/x86/virt/vmx/tdx/tdxcall.S > > > @@ -1,6 +1,7 @@ > > > /* SPDX-License-Identifier: GPL-2.0 */ > > > #include <asm/asm-offsets.h> > > > #include <asm/tdx.h> > > > +#include <asm/asm.h> > > > > > > /* > > > * TDCALL and SEAMCALL are supported in Binutils >= 2.36. > > > @@ -45,6 +46,7 @@ > > > /* Leave input param 2 in RDX */ > > > > > > .if \host > > > +1: > > > seamcall > > > > So what registers are actually clobbered by SEAMCALL ? There's a > > distinct lack of it in SDM Vol.2 instruction list :-( > > With the exception of the abomination that is TDH.VP.ENTER all SEAMCALLs > seem to be limited to the set presented here (c,d,8,9,10,11) and all > other registers should be available. > > Can we please make that a hard requirement, SEAMCALL must not use > registers outside this? We can hardly program to random future > extentions; we need hard ABI guarantees here. > > That also means we should be able to use si,di for the cmovc below. > > Kirill, back when we did __tdx_hypercall() we got bp removed as a valid > register, the 1.0 spec still lists that, and it is also listed in > TDH.VP.ENTER, I'm assuming it will be removed there too? > > bp must not be used -- it violates the pre-existing calling convention. I've just brought it up again internally. Let's see what will happen. -- Kiryl Shutsemau / Kirill A. Shutemov
