On Tue, Sep 08, 2020 at 04:39:35PM +0200, Andrey Konovalov wrote: > On Fri, Aug 14, 2020 at 7:28 PM Andrey Konovalov <andreyknvl@xxxxxxxxxx> wrote: > > From: Vincenzo Frascino <vincenzo.frascino@xxxxxxx> > > > > The Tag Checking operation causes a synchronous data abort as > > a consequence of a tag check fault when MTE is configured in > > synchronous mode. > > > > Enable MTE in Synchronous mode in EL1 to provide a more immediate > > way of tag check failure detection in the kernel. > > > > As part of this change enable match-all tag for EL1 to allow the > > kernel to access user pages without faulting. This is required because > > the kernel does not have knowledge of the tags set by the user in a > > page. > > > > Note: For MTE, the TCF bit field in SCTLR_EL1 affects only EL1 in a > > similar way as TCF0 affects EL0. > > > > Signed-off-by: Vincenzo Frascino <vincenzo.frascino@xxxxxxx> > > --- > > arch/arm64/kernel/cpufeature.c | 6 ++++++ > > 1 file changed, 6 insertions(+) > > > > diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c > > index 4d3abb51f7d4..4d94af19d8f6 100644 > > --- a/arch/arm64/kernel/cpufeature.c > > +++ b/arch/arm64/kernel/cpufeature.c > > @@ -1670,6 +1670,9 @@ static void cpu_enable_mte(struct arm64_cpu_capabilities const *cap) > > write_sysreg_s(0, SYS_TFSR_EL1); > > write_sysreg_s(0, SYS_TFSRE0_EL1); > > > > + /* Enable Match-All at EL1 */ > > + sysreg_clear_set(tcr_el1, 0, SYS_TCR_EL1_TCMA1); > > + > > /* > > * CnP must be enabled only after the MAIR_EL1 register has been set > > * up. Inconsistent MAIR_EL1 between CPUs sharing the same TLB may > > @@ -1687,6 +1690,9 @@ static void cpu_enable_mte(struct arm64_cpu_capabilities const *cap) > > mair &= ~MAIR_ATTRIDX(MAIR_ATTR_MASK, MT_NORMAL_TAGGED); > > mair |= MAIR_ATTRIDX(MAIR_ATTR_NORMAL_TAGGED, MT_NORMAL_TAGGED); > > write_sysreg_s(mair, SYS_MAIR_EL1); > > + > > + /* Enable MTE Sync Mode for EL1 */ > > + sysreg_clear_set(sctlr_el1, SCTLR_ELx_TCF_MASK, SCTLR_ELx_TCF_SYNC); > > isb(); > > > > local_flush_tlb_all(); > > -- > > 2.28.0.220.ged08abb693-goog > > > > Should we change this commit to enable in-kernel MTE only if > KASAN_HW_TAGS is enabled? I think so. We don't currently have any patchset decoupling MTE from KASAN. See my other comment on TCR_EL1.TBI1, you'd need to set TCMA1 as well in the same proc.S file. -- Catalin
