On Sat, 27 Feb 2021 10:42:00 +0000 Alexandru Elisei <alexandru.elisei@xxxxxxx> wrote: Hi, > Some fields in SCTLR_EL1 are UNKNOWN at reset and the arm64 boot > requirements, as stated by Linux in Documentation/arm64/booting.rst, do not > specify a particular value for all the fields. Do not rely on the good will > of the hypervisor and userspace to set SCTLR_EL1 to a sane value (by their > definition of sane) and set SCTLR_EL1 explicitely before running setup(). > This will ensure that all tests are performed with the hardware set up > identically, regardless of the KVM or VMM versions. > > Signed-off-by: Alexandru Elisei <alexandru.elisei@xxxxxxx> Can confirm that the RES1 bits match the ARM ARM, and that it's indeed a good idea to start from a known good state: Reviewed-by: Andre Przywara <andre.przywara@xxxxxxx> Cheers, Andre > --- > lib/arm64/asm/sysreg.h | 7 +++++++ > arm/cstart64.S | 5 +++++ > 2 files changed, 12 insertions(+) > > diff --git a/lib/arm64/asm/sysreg.h b/lib/arm64/asm/sysreg.h > index 9d6b4fc66936..18c4ed39557a 100644 > --- a/lib/arm64/asm/sysreg.h > +++ b/lib/arm64/asm/sysreg.h > @@ -8,6 +8,8 @@ > #ifndef _ASMARM64_SYSREG_H_ > #define _ASMARM64_SYSREG_H_ > > +#include <linux/const.h> > + > #define sys_reg(op0, op1, crn, crm, op2) \ > ((((op0)&3)<<19)|((op1)<<16)|((crn)<<12)|((crm)<<8)|((op2)<<5)) > > @@ -87,4 +89,9 @@ asm( > #define SCTLR_EL1_A (1 << 1) > #define SCTLR_EL1_M (1 << 0) > > +#define SCTLR_EL1_RES1 (_BITUL(7) | _BITUL(8) | _BITUL(11) | _BITUL(20) | \ > + _BITUL(22) | _BITUL(23) | _BITUL(28) | _BITUL(29)) > +#define INIT_SCTLR_EL1_MMU_OFF \ > + SCTLR_EL1_RES1 > + > #endif /* _ASMARM64_SYSREG_H_ */ > diff --git a/arm/cstart64.S b/arm/cstart64.S > index f6c5d2ebccf3..42a838ff4c38 100644 > --- a/arm/cstart64.S > +++ b/arm/cstart64.S > @@ -52,6 +52,11 @@ start: > b 1b > > 1: > + /* set SCTLR_EL1 to a known value */ > + ldr x4, =INIT_SCTLR_EL1_MMU_OFF > + msr sctlr_el1, x4 > + isb > + > /* set up stack */ > mov x4, #1 > msr spsel, x4
