On Mon, 22 Mar 2021 17:40:40 +0000, Quentin Perret <qperret@xxxxxxxxxx> wrote: > > Hey Marc, > > On Monday 22 Mar 2021 at 16:48:27 (+0000), Marc Zyngier wrote: > > In protected mode, late CPUs are not allowed to boot (enforced by > > the PSCI relay). We can thus specialise the read_ctr macro to > > always return a pre-computed, sanitised value. > > > > Signed-off-by: Marc Zyngier <maz@xxxxxxxxxx> > > --- > > arch/arm64/include/asm/assembler.h | 9 +++++++++ > > arch/arm64/kernel/image-vars.h | 1 + > > arch/arm64/kvm/va_layout.c | 7 +++++++ > > 3 files changed, 17 insertions(+) > > > > diff --git a/arch/arm64/include/asm/assembler.h b/arch/arm64/include/asm/assembler.h > > index fb651c1f26e9..1a4cee7eb3c9 100644 > > --- a/arch/arm64/include/asm/assembler.h > > +++ b/arch/arm64/include/asm/assembler.h > > @@ -270,12 +270,21 @@ alternative_endif > > * provide the system wide safe value from arm64_ftr_reg_ctrel0.sys_val > > */ > > .macro read_ctr, reg > > +#ifndef __KVM_NVHE_HYPERVISOR__ > > alternative_if_not ARM64_MISMATCHED_CACHE_TYPE > > mrs \reg, ctr_el0 // read CTR > > nop > > alternative_else > > ldr_l \reg, arm64_ftr_reg_ctrel0 + ARM64_FTR_SYSVAL > > alternative_endif > > +#else > > +alternative_cb kvm_compute_final_ctr_el0 > > + movz \reg, #0 > > + movk \reg, #0, lsl #16 > > + movk \reg, #0, lsl #32 > > + movk \reg, #0, lsl #48 > > +alternative_cb_end > > +#endif > > .endm > > So, FWIW, if we wanted to make _this_ macro BUG in non-protected mode > (and drop patch 01), I think we could do something like: > > alternative_cb kvm_compute_final_ctr_el0 > movz \reg, #0 > ASM_BUG() > nop > nop > alternative_cb_end > > and then make kvm_compute_final_ctr_el0() check that we're in protected > mode before patching. That would be marginally better as that would > cover _all_ users of read_ctr and not just __flush_dcache_area, but that > first movz is a bit yuck (but necessary to keep generate_mov_q() happy I > think?), so I'll leave the decision to you. Can't say I'm keen on the yucky bit, but here's an alternative (ha!) for you: diff --git a/arch/arm64/include/asm/assembler.h b/arch/arm64/include/asm/assembler.h index 1a4cee7eb3c9..7582c3bd2f05 100644 --- a/arch/arm64/include/asm/assembler.h +++ b/arch/arm64/include/asm/assembler.h @@ -278,6 +278,9 @@ alternative_else ldr_l \reg, arm64_ftr_reg_ctrel0 + ARM64_FTR_SYSVAL alternative_endif #else +alternative_if_not ARM64_KVM_PROTECTED_MODE + ASM_BUG() +alternative_else_nop_endif alternative_cb kvm_compute_final_ctr_el0 movz \reg, #0 movk \reg, #0, lsl #16 Yes, it is one more instruction, but it is cleaner and allows us to from the first patch of the series. What do you think? M. -- Without deviation from the norm, progress is not possible. _______________________________________________ kvmarm mailing list kvmarm@xxxxxxxxxxxxxxxxxxxxx https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
