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SubjectRe: [PATCH 08/26] x86/tdx: Handle in-kernel MMIO
On Wed, Dec 15, 2021 at 03:31:16PM -0800, Josh Poimboeuf wrote:
> On Tue, Dec 14, 2021 at 06:02:46PM +0300, Kirill A. Shutemov wrote:
> > @@ -155,6 +157,108 @@ static bool tdx_handle_cpuid(struct pt_regs *regs)
> > return true;
> > }
> >
> > +static bool tdx_mmio(int size, bool write, unsigned long addr,
> > + unsigned long *val)
> > +{
> > + struct tdx_hypercall_output out;
> > + u64 err;
> > +
> > + err = _tdx_hypercall(EXIT_REASON_EPT_VIOLATION, size, write,
> > + addr, *val, &out);
> > + if (err)
> > + return true;
> > +
> > + *val = out.r11;
> > + return false;
> > +}
> > +
> > +static bool tdx_mmio_read(int size, unsigned long addr, unsigned long *val)
> > +{
> > + return tdx_mmio(size, false, addr, val);
> > +}
> > +
> > +static bool tdx_mmio_write(int size, unsigned long addr, unsigned long *val)
> > +{
> > + return tdx_mmio(size, true, addr, val);
> > +}
>
> These bool functions return false on success. Conversely, other
> functions in this file return true on success. That inconsistency is
> really confusing for the callers and is bound to introduce bugs
> eventually.
>
> > +static int tdx_handle_mmio(struct pt_regs *regs, struct ve_info *ve)
>
> Similarly, tdx_handle_mmio() returns (int) 0 for success, while other
> tdx_handle_*() functions return (bool) true for success. Also
> confusing.
>
> The most robust option would be for all the functions to follow the
> typical kernel convention of returning (int) 0 on success. It works for
> 99.99% of the kernel. Why mess with success? (pun intended)
>
> Otherwise it's just pointless added cognitive overhead, trying to keep
> track of what success means, for each individual function.

Okay, fair enough. I will make them consistent.

--
Kirill A. Shutemov

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