Messages in this thread | | | Date | Fri, 17 Jul 2020 13:52:55 -0700 | From | Ira Weiny <> | Subject | Re: [PATCH RFC V2 02/17] x86/fpu: Refactor arch_set_user_pkey_access() for PKS support |
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On Fri, Jul 17, 2020 at 10:54:42AM +0200, Peter Zijlstra wrote: > On Fri, Jul 17, 2020 at 12:20:41AM -0700, ira.weiny@intel.com wrote: > > +/* > > + * Get a new pkey register value from the user values specified. > > + * > > + * Kernel users use the same flags as user space: > > + * PKEY_DISABLE_ACCESS > > + * PKEY_DISABLE_WRITE > > + */ > > +u32 get_new_pkr(u32 old_pkr, int pkey, unsigned long init_val) > > +{ > > + int pkey_shift = (pkey * PKR_BITS_PER_PKEY); > > + u32 new_pkr_bits = 0; > > + > > + /* Set the bits we need in the register: */ > > + if (init_val & PKEY_DISABLE_ACCESS) > > + new_pkr_bits |= PKR_AD_BIT; > > + if (init_val & PKEY_DISABLE_WRITE) > > + new_pkr_bits |= PKR_WD_BIT; > > + > > + /* Shift the bits in to the correct place: */ > > + new_pkr_bits <<= pkey_shift; > > + > > + /* Mask off any old bits in place: */ > > + old_pkr &= ~((PKR_AD_BIT | PKR_WD_BIT) << pkey_shift); > > + > > + /* Return the old part along with the new part: */ > > + return old_pkr | new_pkr_bits; > > +} > > This is unbelievable junk... > > How about something like: > > u32 update_pkey_reg(u32 pk_reg, int pkey, unsigned int flags) > { > int pkey_shift = pkey * PKR_BITS_PER_PKEY; > > pk_reg &= ~(((1 << PKR_BITS_PER_PKEY) - 1) << pkey_shift); > > if (flags & PKEY_DISABLE_ACCESS) > pk_reg |= PKR_AD_BIT << pkey_shift; > if (flags & PKEY_DISABLE_WRITE) > pk_reg |= PKR_WD_BIT << pkey_shift; > > return pk_reg; > } > > Then we at least have a little clue wtf the thing does.. Yes I started > with a rename and then got annoyed at the implementation too.
On the code I think this is fair. I've also updated the calling function to be a bit cleaner as well.
However, I think the name 'update' is a bit misleading. Here is the new calling code:
... pkru = read_pkru(); pkru = update_pkey_reg(pkru, pkey, init_val); write_pkru(pkru); ...
I think it is odd to have a function called update_pkey_reg() called right before a write_pkru(). Can we call this update_pkey_value? or just 'val'? Because write_pkru() actually updates the register.
Thanks for the review, Ira
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