Messages in this thread Patch in this message | | | Date | Thu, 18 Jun 2020 17:34:40 +0100 | From | Marc Zyngier <> | Subject | Re: [PATCH v3 03/15] arm64: kvm: Add build rules for separate nVHE object files |
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Hi David,
On 2020-06-18 13:25, David Brazdil wrote: > Add new folder arch/arm64/kvm/hyp/nvhe and a Makefile for building code > that > runs in EL2 under nVHE KVM. > > Compile each source file into a `.hyp.tmp.o` object first, then prefix > all > its symbols with "__kvm_nvhe_" using `objcopy` and produce a `.hyp.o`. > Suffixes were chosen so that it would be possible for VHE and nVHE to > share > some source files, but compiled with different CFLAGS. nVHE build rules > add > -D__KVM_NVHE_HYPERVISOR__. > > The nVHE ELF symbol prefix is added to kallsyms.c as ignored. EL2-only > symbols > will never appear in EL1 stack traces. > > Signed-off-by: David Brazdil <dbrazdil@google.com> > --- > arch/arm64/kernel/image-vars.h | 12 +++++++++++ > arch/arm64/kvm/hyp/Makefile | 2 +- > arch/arm64/kvm/hyp/nvhe/Makefile | 35 ++++++++++++++++++++++++++++++++ > scripts/kallsyms.c | 1 + > 4 files changed, 49 insertions(+), 1 deletion(-) > create mode 100644 arch/arm64/kvm/hyp/nvhe/Makefile > > diff --git a/arch/arm64/kernel/image-vars.h > b/arch/arm64/kernel/image-vars.h > index be0a63ffed23..f32b406e90c0 100644 > --- a/arch/arm64/kernel/image-vars.h > +++ b/arch/arm64/kernel/image-vars.h > @@ -51,4 +51,16 @@ __efistub__ctype = _ctype; > > #endif > > +#ifdef CONFIG_KVM > + > +/* > + * KVM nVHE code has its own symbol namespace prefixed by __kvm_nvhe_, > to > + * isolate it from the kernel proper. The following symbols are > legally > + * accessed by it, therefore provide aliases to make them linkable. > + * Do not include symbols which may not be safely accessed under > hypervisor > + * memory mappings. > + */ > + > +#endif /* CONFIG_KVM */ > + > #endif /* __ARM64_KERNEL_IMAGE_VARS_H */ > diff --git a/arch/arm64/kvm/hyp/Makefile b/arch/arm64/kvm/hyp/Makefile > index 5d8357ddc234..5f4f217532e0 100644 > --- a/arch/arm64/kvm/hyp/Makefile > +++ b/arch/arm64/kvm/hyp/Makefile > @@ -6,7 +6,7 @@ > ccflags-y += -fno-stack-protector -DDISABLE_BRANCH_PROFILING \ > $(DISABLE_STACKLEAK_PLUGIN) > > -obj-$(CONFIG_KVM) += hyp.o > +obj-$(CONFIG_KVM) += hyp.o nvhe/ > obj-$(CONFIG_KVM_INDIRECT_VECTORS) += smccc_wa.o > > hyp-y := vgic-v3-sr.o timer-sr.o aarch32.o vgic-v2-cpuif-proxy.o > sysreg-sr.o \ > diff --git a/arch/arm64/kvm/hyp/nvhe/Makefile > b/arch/arm64/kvm/hyp/nvhe/Makefile > new file mode 100644 > index 000000000000..7d64235dba62 > --- /dev/null > +++ b/arch/arm64/kvm/hyp/nvhe/Makefile > @@ -0,0 +1,35 @@ > +# SPDX-License-Identifier: GPL-2.0 > +# > +# Makefile for Kernel-based Virtual Machine module, HYP/nVHE part > +# > + > +asflags-y := -D__KVM_NVHE_HYPERVISOR__ > +ccflags-y := -D__KVM_NVHE_HYPERVISOR__ -fno-stack-protector \ > + -DDISABLE_BRANCH_PROFILING $(DISABLE_STACKLEAK_PLUGIN) > + > +obj-y := > + > +obj-y := $(patsubst %.o,%.hyp.o,$(obj-y)) > +extra-y := $(patsubst %.hyp.o,%.hyp.tmp.o,$(obj-y)) > + > +$(obj)/%.hyp.tmp.o: $(src)/%.c FORCE > + $(call if_changed_rule,cc_o_c) > +$(obj)/%.hyp.tmp.o: $(src)/%.S FORCE > + $(call if_changed_rule,as_o_S) > +$(obj)/%.hyp.o: $(obj)/%.hyp.tmp.o FORCE > + $(call if_changed,hypcopy) > + > +quiet_cmd_hypcopy = HYPCOPY $@ > + cmd_hypcopy = $(OBJCOPY) --prefix-symbols=__kvm_nvhe_ $< $@ > + > +# KVM nVHE code is run at a different exception code with a different > map, so > +# compiler instrumentation that inserts callbacks or checks into the > code may > +# cause crashes. Just disable it. > +GCOV_PROFILE := n > +KASAN_SANITIZE := n > +UBSAN_SANITIZE := n > +KCOV_INSTRUMENT := n > + > +# Skip objtool checking for this directory because nVHE code is > compiled with > +# non-standard build rules. > +OBJECT_FILES_NON_STANDARD := y > diff --git a/scripts/kallsyms.c b/scripts/kallsyms.c > index 6dc3078649fa..0096cd965332 100644 > --- a/scripts/kallsyms.c > +++ b/scripts/kallsyms.c > @@ -109,6 +109,7 @@ static bool is_ignored_symbol(const char *name, > char type) > ".LASANPC", /* s390 kasan local symbols */ > "__crc_", /* modversions */ > "__efistub_", /* arm64 EFI stub namespace */ > + "__kvm_nvhe_", /* arm64 non-VHE KVM namespace */ > NULL > };
I guess that one of the first use of this __KVM_NVHE_HYPERVISOR__ flag could be the has_vhe() predicate: if you're running the nVHE code, you are *guaranteed* not to use VHE at all.
Something like:
diff --git a/arch/arm64/include/asm/virt.h b/arch/arm64/include/asm/virt.h index 5051b388c654..b2cb8fce43dd 100644 --- a/arch/arm64/include/asm/virt.h +++ b/arch/arm64/include/asm/virt.h @@ -85,10 +85,8 @@ static inline bool is_kernel_in_hyp_mode(void)
static __always_inline bool has_vhe(void) { - if (cpus_have_final_cap(ARM64_HAS_VIRT_HOST_EXTN)) - return true; - - return false; + return (__is_defined(__KVM_NVHE_HYPERVISOR__) && + cpus_have_final_cap(ARM64_HAS_VIRT_HOST_EXTN)); }
#endif /* __ASSEMBLY__ */ Thanks,
M. -- Jazz is not dead. It just smells funny...
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