Re: [PATCH v5 14/36] KVM: arm64: Provide __flush_dcache_area at EL2

On Monday 15 Mar 2021 at 16:33:23 (+0000), Will Deacon wrote:

On Mon, Mar 15, 2021 at 02:35:14PM +0000, Quentin Perret wrote:

quoted

We will need to do cache maintenance at EL2 soon, so compile a copy of
__flush_dcache_area at EL2, and provide a copy of arm64_ftr_reg_ctrel0
as it is needed by the read_ctr macro.

Signed-off-by: Quentin Perret <redacted>
---
 arch/arm64/include/asm/kvm_cpufeature.h |  2 ++
 arch/arm64/kvm/hyp/nvhe/Makefile        |  3 ++-
 arch/arm64/kvm/hyp/nvhe/cache.S         | 13 +++++++++++++
 arch/arm64/kvm/sys_regs.c               |  1 +
 4 files changed, 18 insertions(+), 1 deletion(-)
 create mode 100644 arch/arm64/kvm/hyp/nvhe/cache.S

diff --git a/arch/arm64/include/asm/kvm_cpufeature.h b/arch/arm64/include/asm/kvm_cpufeature.h
index 3fd9f60d2180..efba1b89b8a4 100644
--- a/arch/arm64/include/asm/kvm_cpufeature.h
+++ b/arch/arm64/include/asm/kvm_cpufeature.h

@@ -13,3 +13,5 @@
 #define KVM_HYP_CPU_FTR_REG(name) extern struct arm64_ftr_reg kvm_nvhe_sym(name)
 #endif
 #endif
+
+KVM_HYP_CPU_FTR_REG(arm64_ftr_reg_ctrel0);

I still think this is a bit weird. If you really want to macro-ise stuff,
then why not follow the sort of thing we do for e.g. per-cpu variables and
have separate DECLARE_HYP_CPU_FTR_REG and DEFINE_HYP_CPU_FTR_REG macros.

That way kvm_cpufeature.h can have header guards like a normal header and
we can drop the '#ifndef KVM_HYP_CPU_FTR_REG' altogether. I don't think
the duplication of the symbol name really matters -- it should fail at
build time if something is missing.

I just tend to hate unnecessary boilerplate, but if you feel strongly
about it, happy to change :)

Cheers,
Quentin

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