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charset=us-ascii Content-Disposition: inline In-Reply-To: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260805_022103_003636_585BF779 X-CRM114-Status: GOOD ( 29.46 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hi, On Tue, Aug 04, 2026 at 02:51:28PM +0100, Will Deacon wrote: > On Mon, Aug 03, 2026 at 09:22:02AM +0530, Linu Cherian wrote: > > Hi Will, > > > > On Fri, Jul 31, 2026 at 04:13:20PM +0100, Will Deacon wrote: > > > On Thu, Jul 23, 2026 at 10:10:33AM +0530, Linu Cherian wrote: > > > > Add ID_AA64MMFR2_EL1.BBM based BBML3 feature detection in > > > > cpu_supports_bbml3() so that cpus with the feature would > > > > not have to be added into MIDR based supports_bbml3_list. > > > > > > > > Reviewed-by: Gavin Shan > > > > Reviewed-by: Anshuman Khandual > > > > Signed-off-by: Linu Cherian > > > > --- > > > > arch/arm64/kernel/cpufeature.c | 17 +++++++++-------- > > > > 1 file changed, 9 insertions(+), 8 deletions(-) > > > > > > > > diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c > > > > index 896bafdb00b1..dbd7d187520c 100644 > > > > --- a/arch/arm64/kernel/cpufeature.c > > > > +++ b/arch/arm64/kernel/cpufeature.c > > > > @@ -2133,6 +2133,12 @@ static bool hvhe_possible(const struct arm64_cpu_capabilities *entry, > > > > > > > > bool cpu_supports_bbml3(void) > > > > { > > > > + u64 mmfr2; > > > > + > > > > + mmfr2 = __read_sysreg_by_encoding(SYS_ID_AA64MMFR2_EL1); > > > > + if (SYS_FIELD_GET(ID_AA64MMFR2_EL1, BBM, mmfr2) >= ID_AA64MMFR2_EL1_BBM_3) > > > > + return true; > > > > > > This is a bit of a nit, but I think it would be more consistent to use > > > has_cpuid_feature() here instead of __read_sysreg_by_encoding(), similarly > > > to how we handle kpti in unmap_kernel_at_el0() (which also has both an > > > ID register field and a list of MIDRs). > > > > force_pte_mapping required by map_mem(during early boot) needs > > cpu_supports_bbml3 check and cpu features/capabilities are not > > initialized by that time. Should i add a comment there to clarify this ? > > It looks to me like has_cpuid_feature() will call > __read_sysreg_by_encoding() under the hood for SCOPE_LOCAL_CPU. > > What am I missing? Below is my understanding. Correct me if i am wrong. has_cpuid_feature depends on struct arm64_cpu_capabilities *entry. Inorder to derive *entry from a capability ID, cpucap_ptrs should be in initialized state and that wont be the case when force_pte_mapping invokes cpu_supports_bbml3. > > Will