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Mon, 08 Jun 2020 08:00:39 -0700 (PDT) Date: Mon, 8 Jun 2020 16:00:35 +0100 From: Andrew Scull To: Marc Zyngier Cc: kvm@vger.kernel.org, kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org, James Morse , Julien Thierry , Suzuki K Poulose , kernel-team@android.com Subject: Re: [PATCH] KVM: arm64: Stop sparse from moaning at __hyp_this_cpu_ptr Message-ID: <20200608150035.GB96714@google.com> References: <20200608085731.1405854-1-maz@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200608085731.1405854-1-maz@kernel.org> Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org 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 > --- > 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? > + * a data structure. As for SHIFT_PERCPU_PTR(), the creative casting keeps > + * sparse quiet. > + */ > #define __hyp_this_cpu_ptr(sym) \ > ({ \ > void *__ptr = hyp_symbol_addr(sym); \ > __ptr += read_sysreg(tpidr_el2); \ > - (typeof(&sym))__ptr; \ > + (typeof(sym) __kernel __force *)__ptr; \ > }) > > #define __hyp_this_cpu_read(sym) \