Messages in this thread | ![/](/images/icornerl.gif) | | Subject | Re: [PATCH 1/6] arm64: kpti: move check for non-vulnerable CPUs to a function | From | Julien Thierry <> | Date | Thu, 13 Dec 2018 09:13:36 +0000 |
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Hi,
On 06/12/2018 23:44, Jeremy Linton wrote: > From: Mian Yousaf Kaukab <ykaukab@suse.de> > > Add is_meltdown_safe() which is a whitelist of known safe cores. > > Signed-off-by: Mian Yousaf Kaukab <ykaukab@suse.de> > [Moved location of function] > Signed-off-by: Jeremy Linton <jeremy.linton@arm.com> > --- > arch/arm64/kernel/cpufeature.c | 16 ++++++++++++---- > 1 file changed, 12 insertions(+), 4 deletions(-) > > diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c > index aec5ecb85737..242898395f68 100644 > --- a/arch/arm64/kernel/cpufeature.c > +++ b/arch/arm64/kernel/cpufeature.c > @@ -908,8 +908,7 @@ has_useable_cnp(const struct arm64_cpu_capabilities *entry, int scope) > #ifdef CONFIG_UNMAP_KERNEL_AT_EL0 > static int __kpti_forced; /* 0: not forced, >0: forced on, <0: forced off */ > > -static bool unmap_kernel_at_el0(const struct arm64_cpu_capabilities *entry, > - int scope) > +static bool is_cpu_meltdown_safe(void) > { > /* List of CPUs that are not vulnerable and don't need KPTI */ > static const struct midr_range kpti_safe_list[] = { > @@ -917,6 +916,16 @@ static bool unmap_kernel_at_el0(const struct arm64_cpu_capabilities *entry, > MIDR_ALL_VERSIONS(MIDR_BRCM_VULCAN), > { /* sentinel */ } > }; > + /* Don't force KPTI for CPUs that are not vulnerable */
This is really a nit, but that comment would make more sense where is_cpu_meltdown_safe() is called since unmap_kernel_at_el0 is the one deciding whether to apply KPTI, is_cpu_meltdown_safe() just states whether the core is safe of not.
Otherwise:
Reviewed-by: Julien Thierry <julien.thierry@arm.com>
Cheers,
Julien
> + if (is_midr_in_range_list(read_cpuid_id(), kpti_safe_list)) > + return true; > + > + return false; > +} > + > +static bool unmap_kernel_at_el0(const struct arm64_cpu_capabilities *entry, > + int scope) > +{ > char const *str = "command line option"; > > /* > @@ -940,8 +949,7 @@ static bool unmap_kernel_at_el0(const struct arm64_cpu_capabilities *entry, > if (IS_ENABLED(CONFIG_RANDOMIZE_BASE)) > return true; > > - /* Don't force KPTI for CPUs that are not vulnerable */ > - if (is_midr_in_range_list(read_cpuid_id(), kpti_safe_list)) > + if (is_cpu_meltdown_safe()) > return false; > > /* Defer to CPU feature registers */ >
-- Julien Thierry
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