linux-kernel - Re: [RFC 04/14] KVM: x86/MMU: Expose functions for paging

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Message-ID: <Y7h7QPI5YcJ/FO02@google.com>
Date:   Fri, 6 Jan 2023 11:49:20 -0800
From:   David Matlack <dmatlack@...gle.com>
To:     Ben Gardon <bgardon@...gle.com>
Cc:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        Paolo Bonzini <pbonzini@...hat.com>,
        Peter Xu <peterx@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Vipin Sharma <vipinsh@...gle.com>,
        Nagareddy Reddy <nspreddy@...gle.com>
Subject: Re: [RFC 04/14] KVM: x86/MMU: Expose functions for paging_tmpl.h

On Wed, Dec 21, 2022 at 10:24:08PM +0000, Ben Gardon wrote:
> In preparation for moving paging_tmpl.h to shadow_mmu.c, expose various
> functions it needs through mmu_internal.h. This includes modifying the
> BUILD_MMU_ROLE_ACCESSOR macro so that it does not automatically include
> the static label, since some but not all of the accessors are needed by
> paging_tmpl.h.
> 
> No functional change intended.
> 
> Signed-off-by: Ben Gardon <bgardon@...gle.com>
> ---
>  arch/x86/kvm/mmu/mmu.c          | 32 ++++++++++++++++----------------
>  arch/x86/kvm/mmu/mmu_internal.h | 16 ++++++++++++++++
>  2 files changed, 32 insertions(+), 16 deletions(-)
> 
> diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> index bf14e181eb12..a17e8a79e4df 100644
> --- a/arch/x86/kvm/mmu/mmu.c
> +++ b/arch/x86/kvm/mmu/mmu.c
> @@ -153,18 +153,18 @@ BUILD_MMU_ROLE_REGS_ACCESSOR(efer, lma, EFER_LMA);
>   * and the vCPU may be incorrect/irrelevant.
>   */
>  #define BUILD_MMU_ROLE_ACCESSOR(base_or_ext, reg, name)		\
> -static inline bool __maybe_unused is_##reg##_##name(struct kvm_mmu *mmu)	\
> +inline bool __maybe_unused is_##reg##_##name(struct kvm_mmu *mmu)	\
>  {								\
>  	return !!(mmu->cpu_role. base_or_ext . reg##_##name);	\
>  }
>  BUILD_MMU_ROLE_ACCESSOR(base, cr0, wp);
> -BUILD_MMU_ROLE_ACCESSOR(ext,  cr4, pse);
> +static BUILD_MMU_ROLE_ACCESSOR(ext,  cr4, pse);
>  BUILD_MMU_ROLE_ACCESSOR(ext,  cr4, smep);
> -BUILD_MMU_ROLE_ACCESSOR(ext,  cr4, smap);
> -BUILD_MMU_ROLE_ACCESSOR(ext,  cr4, pke);
> -BUILD_MMU_ROLE_ACCESSOR(ext,  cr4, la57);
> +static BUILD_MMU_ROLE_ACCESSOR(ext,  cr4, smap);
> +static BUILD_MMU_ROLE_ACCESSOR(ext,  cr4, pke);
> +static BUILD_MMU_ROLE_ACCESSOR(ext,  cr4, la57);
>  BUILD_MMU_ROLE_ACCESSOR(base, efer, nx);
> -BUILD_MMU_ROLE_ACCESSOR(ext,  efer, lma);
> +static BUILD_MMU_ROLE_ACCESSOR(ext,  efer, lma);

Suggest moving all the BUILD_MMU_ROLE*() macros to mmu_internal.h, since
they are already static inline. That would be a cleaner patch and reduce
future churn if shadow_mmu.c ever needs to use a different role accessor
at some point.

>  
>  static inline bool is_cr0_pg(struct kvm_mmu *mmu)
>  {
> @@ -210,7 +210,7 @@ void kvm_flush_remote_tlbs_with_address(struct kvm *kvm,
>  	kvm_flush_remote_tlbs_with_range(kvm, &range);
>  }
>  
> -static gfn_t get_mmio_spte_gfn(u64 spte)
> +gfn_t get_mmio_spte_gfn(u64 spte)
>  {
>  	u64 gpa = spte & shadow_nonpresent_or_rsvd_lower_gfn_mask;
>  
> @@ -240,7 +240,7 @@ static bool check_mmio_spte(struct kvm_vcpu *vcpu, u64 spte)
>  	return likely(kvm_gen == spte_gen);
>  }
>  
> -static int is_cpuid_PSE36(void)
> +int is_cpuid_PSE36(void)
>  {
>  	return 1;
>  }

Can we just drop is_cpuid_PSE36(), e.g. as a precursor patch? It just
returns 1...