On Tue, Sep 08, 2020 at 03:18:04PM +0200, Andrey Konovalov wrote: > On Thu, Aug 27, 2020 at 12:40 PM Catalin Marinas > <catalin.marinas@xxxxxxx> wrote: > > > > On Fri, Aug 14, 2020 at 07:27:08PM +0200, Andrey Konovalov wrote: > > > diff --git a/arch/arm64/mm/proc.S b/arch/arm64/mm/proc.S > > > index 152d74f2cc9c..6880ddaa5144 100644 > > > --- a/arch/arm64/mm/proc.S > > > +++ b/arch/arm64/mm/proc.S > > > @@ -38,7 +38,7 @@ > > > /* PTWs cacheable, inner/outer WBWA */ > > > #define TCR_CACHE_FLAGS TCR_IRGN_WBWA | TCR_ORGN_WBWA > > > > > > -#ifdef CONFIG_KASAN_SW_TAGS > > > +#if defined(CONFIG_KASAN_SW_TAGS) || defined(CONFIG_KASAN_HW_TAGS) > > > #define TCR_KASAN_FLAGS TCR_TBI1 > > > #else > > > #define TCR_KASAN_FLAGS 0 > > > > I prefer to turn TBI1 on only if MTE is present. So on top of the v8 > > user series, just do this in __cpu_setup. > > Started working on this, but realized that I don't understand what > exactly is suggested here. TCR_KASAN_FLAGS are used in __cpu_setup(), > so this already happens in __cpu_setup(). > > Do you mean that TBI1 should be enabled when CONFIG_ARM64_MTE is > enabled, but CONFIG_KASAN_HW_TAGS is disabled? What I meant is that we should turn TBI1 only when the MTE is present in hardware (and the ARM64_MTE option is on). But I probably missed the way MTE is used with KASAN. So what happens if CONFIG_KASAN_HW_TAGS and CONFIG_ARM64_MTE are both on but the hardware does not support MTE? Does KASAN still generate tagged pointers? If yes, then the current patch is fine, we should always set TBI1. -- Catalin
