On Fri, 2023-09-08 at 09:21 -0700, Dave Hansen wrote:
> On 8/25/23 05:14, Kai Huang wrote:
> > Some SEAMCALLs use the RDRAND hardware and can fail for the same reasons
> > as RDRAND. Use the kernel RDRAND retry logic for them.
> >
> > There are three __seamcall*() variants. Add a macro to do the SEAMCALL
> > retry in the common code and define a wrapper for each __seamcall*()
> > variant.
> >
> > Signed-off-by: Kai Huang <kai.huang@xxxxxxxxx>
> > ---
> >
> > v12 -> v13:
> > - New implementation due to TDCALL assembly series.
> >
> > ---
> > arch/x86/include/asm/tdx.h | 27 +++++++++++++++++++++++++++
> > 1 file changed, 27 insertions(+)
> >
> > diff --git a/arch/x86/include/asm/tdx.h b/arch/x86/include/asm/tdx.h
> > index a252328734c7..cfae8b31a2e9 100644
> > --- a/arch/x86/include/asm/tdx.h
> > +++ b/arch/x86/include/asm/tdx.h
> > @@ -24,6 +24,11 @@
> > #define TDX_SEAMCALL_GP (TDX_SW_ERROR | X86_TRAP_GP)
> > #define TDX_SEAMCALL_UD (TDX_SW_ERROR | X86_TRAP_UD)
> >
> > +/*
> > + * TDX module SEAMCALL leaf function error codes
> > + */
> > +#define TDX_RND_NO_ENTROPY 0x8000020300000000ULL
> > +
> > #ifndef __ASSEMBLY__
> >
> > /*
> > @@ -82,6 +87,28 @@ u64 __seamcall(u64 fn, struct tdx_module_args *args);
> > u64 __seamcall_ret(u64 fn, struct tdx_module_args *args);
> > u64 __seamcall_saved_ret(u64 fn, struct tdx_module_args *args);
> >
> > +#include <asm/archrandom.h>
> > +
> > +#define SEAMCALL_NO_ENTROPY_RETRY(__seamcall_func, __fn, __args) \
> > +({ \
> > + int ___retry = RDRAND_RETRY_LOOPS; \
> > + u64 ___sret; \
> > + \
> > + do { \
> > + ___sret = __seamcall_func((__fn), (__args)); \
> > + } while (___sret == TDX_RND_NO_ENTROPY && --___retry); \
> > + ___sret; \
> > +})
>
> This is a *LOT* less eye-bleedy if you do it without macros:
>
>
> typedef u64 (*sc_func_t)(u64 fn, struct tdx_module_args *args);
>
> static inline
> u64 sc_retry(sc_func_t func, u64 fn, struct tdx_module_args *args)
> {
> int retry = RDRAND_RETRY_LOOPS;
> u64 ret;
>
> do {
> ret = func(fn, args);
> } while (ret == TDX_RND_NO_ENTROPY && --retry);
>
> return ret;
> }
>
> #define seamcall(_fn, _args) sc_retry(_seamcall,
> (_fn), (_args))
> #define seamcall_ret(_fn, _args) sc_retry(_seamcall_ret,
> (_fn), (_args))
> #define seamcall_saved_ret(_fn, _args) sc_retry(_seamcall_saved_ret,
> (_fn), (_args))
>
> The compiler can figure it out and avoid making func() an indirect call
> since it knows the call location at compile time.
Indirect call was a concern when I was implementing those. I didn't know for
sure that the compiler can avoid it. I'll change to use above. Thanks!
>
> You can also do the seamcall() #define as a static inline, but it does
> take up more screen real estate. Oh, and going a wee bit over 80
> columns is OK for those #defines.
Yes I verified the checkpatch.pl wouldn't complain if the #define exceeded 80
characters in one line. I'll use #define. Thanks!
