Re: [PATCH] KVM: arm64: Stop sparse from moaning at __hyp_this_cpu_ptr

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On 2020-06-08 16:00, Andrew Scull wrote:
On Mon, Jun 08, 2020 at 09:57:31AM +0100, Marc Zyngier wrote:
Sparse complains that __hyp_this_cpu_ptr() returns something
that is flagged noderef and not in the correct address space
(both being the result of the __percpu annotation).

Pretend that __hyp_this_cpu_ptr() knows what it is doing by
forcefully casting the pointer with __kernel __force.

Signed-off-by: Marc Zyngier <maz@xxxxxxxxxx>
---
 arch/arm64/include/asm/kvm_asm.h | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/include/asm/kvm_asm.h b/arch/arm64/include/asm/kvm_asm.h
index 0c9b5fc4ba0a..82691406d493 100644
--- a/arch/arm64/include/asm/kvm_asm.h
+++ b/arch/arm64/include/asm/kvm_asm.h
@@ -81,12 +81,17 @@ extern u32 __kvm_get_mdcr_el2(void);

 extern char __smccc_workaround_1_smc[__SMCCC_WORKAROUND_1_SMC_SZ];

-/* Home-grown __this_cpu_{ptr,read} variants that always work at HYP */
+/*
+ * Home-grown __this_cpu_{ptr,read} variants that always work at HYP,
+ * provided that sym is really a *symbol* and not a pointer obtained from

Look at `this_cpu_ptr` one thing that stood out was `__verify_pcpu_ptr`
that is documented to be suitable for used in custom per CPU macros. I
didn't get how it worked (a type check?)  but maybe it would work here
to validate the argment was indeed a per CPU symbol?

It only works for sparse, but that is definitely a good addition while
we're fixing the sparse compliance.

Thanks,

      M.
--
Jazz is not dead. It just smells funny...



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