On Tue, 2018-03-13 at 15:49 +0300, Kirill A. Shutemov wrote:
> On Tue, Mar 13, 2018 at 03:12:02PM +1300, Kai Huang wrote:
> > It seems setup_pku() will call get_cpu_cap to restore c-
> > >x86_phys_bits
> > later? In which case I think you need to change setup_pku as well.
>
> Thanks for catching this.
>
> I think setup_pku() shouldn't call get_cpu_cap().
>
> Any objections against this:
>
> diff --git a/arch/x86/kernel/cpu/common.c
> b/arch/x86/kernel/cpu/common.c
> index 348cf4821240..ce10d8ae4cd6 100644
> --- a/arch/x86/kernel/cpu/common.c
> +++ b/arch/x86/kernel/cpu/common.c
> @@ -362,6 +362,8 @@ static bool pku_disabled;
>
> static __always_inline void setup_pku(struct cpuinfo_x86 *c)
> {
> + u32 eax, ebx, ecx, edx;
> +
> /* check the boot processor, plus compile options for PKU: */
> if (!cpu_feature_enabled(X86_FEATURE_PKU))
> return;
> @@ -377,7 +379,8 @@ static __always_inline void setup_pku(struct
> cpuinfo_x86 *c)
> * cpuid bit to be set. We need to ensure that we
> * update that bit in this CPU's "cpu_info".
> */
> - get_cpu_cap(c);
> + cpuid_count(0x00000007, 0, &eax, &ebx, &ecx, &edx);
> + c->x86_capability[CPUID_7_ECX] = ecx;
> }
>
> #ifdef CONFIG_X86_INTEL_MEMORY_PROTECTION_KEYS
>
> > And for the comments here, I think it can be refined. It is true
> > that
> > VM guest needs to know bits of physical address, but this info is
> > not
> > used only by VM. I think the reason we need to update is this is
> > simply
> > the fact.
>
> Fair enough. Like this?
Yes good to me. Thanks.
Thanks,
-Kai
>
> diff --git a/arch/x86/kernel/cpu/intel.c
> b/arch/x86/kernel/cpu/intel.c
> index e8ddc6dcfd53..ac45ba7398d9 100644
> --- a/arch/x86/kernel/cpu/intel.c
> +++ b/arch/x86/kernel/cpu/intel.c
> @@ -612,11 +612,8 @@ static void detect_tme(struct cpuinfo_x86 *c)
> #endif
>
> /*
> - * Exclude KeyID bits from physical address bits.
> - *
> - * We have to do this even if we are not going to use KeyID
> bits
> - * ourself. VM guests still have to know that these bits are
> not usable
> - * for physical address.
> + * KeyID bits effectively lower number of physical address
> bits.
> + * Let's update cpuinfo_x86::x86_phys_bits to reflect the
> fact.
> */
> c->x86_phys_bits -= keyid_bits;
> }
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