linux-kernel - Re: [PATCH V2 1/8] kvm: x86/mmu: Use KVM_MMU_ROOT_XXX for kvm_mmu_invalidate

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Date:   Fri, 10 Feb 2023 00:50:22 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     Lai Jiangshan <jiangshanlai@...il.com>
Cc:     linux-kernel@...r.kernel.org, Paolo Bonzini <pbonzini@...hat.com>,
        Lai Jiangshan <jiangshan.ljs@...group.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>, kvm@...r.kernel.org
Subject: Re: [PATCH V2 1/8] kvm: x86/mmu: Use KVM_MMU_ROOT_XXX for
 kvm_mmu_invalidate_gva()

On Tue, Feb 07, 2023, Lai Jiangshan wrote:
> diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> index c91ee2927dd7..958e8eb977ed 100644
> --- a/arch/x86/kvm/mmu/mmu.c
> +++ b/arch/x86/kvm/mmu/mmu.c
> @@ -5707,10 +5707,12 @@ int noinline kvm_mmu_page_fault(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa, u64 err
>  EXPORT_SYMBOL_GPL(kvm_mmu_page_fault);
>  
>  void kvm_mmu_invalidate_gva(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu,
> -			    gva_t gva, hpa_t root_hpa)
> +			    gva_t gva, unsigned long roots)
>  {
>  	int i;
>  
> +	WARN_ON_ONCE(roots & ~KVM_MMU_ROOTS_ALL);

This does nothing since KVM_MMU_ROOTS_ALL is ~0ul.  What I wanted is below, can
you slot that it?  Compile tested only.

--
From: Sean Christopherson <seanjc@...gle.com>
Date: Thu, 9 Feb 2023 16:37:43 -0800
Subject: [PATCH 2/8] KVM: x86/mmu: Sanity check input to kvm_mmu_free_roots()

Tweak KVM_MMU_ROOTS_ALL to precisely cover all current+previous root
flags, and add a sanity in kvm_mmu_free_roots() to verify that the set
of roots to free doesn't stray outside KVM_MMU_ROOTS_ALL.

Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 arch/x86/include/asm/kvm_host.h | 8 ++++----
 arch/x86/kvm/mmu/mmu.c          | 2 ++
 2 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 4d2bc08794e4..01d34f7d009d 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -422,6 +422,10 @@ struct kvm_mmu_root_info {
 
 #define KVM_MMU_NUM_PREV_ROOTS 3
 
+#define KVM_MMU_ROOT_CURRENT		BIT(0)
+#define KVM_MMU_ROOT_PREVIOUS(i)	BIT(1+i)
+#define KVM_MMU_ROOTS_ALL		(BIT(1 + KVM_MMU_NUM_PREV_ROOTS) - 1)
+
 #define KVM_HAVE_MMU_RWLOCK
 
 struct kvm_mmu_page;
@@ -1978,10 +1982,6 @@ static inline int __kvm_irq_line_state(unsigned long *irq_state,
 	return !!(*irq_state);
 }
 
-#define KVM_MMU_ROOT_CURRENT		BIT(0)
-#define KVM_MMU_ROOT_PREVIOUS(i)	BIT(1+i)
-#define KVM_MMU_ROOTS_ALL		(~0UL)
-
 int kvm_pic_set_irq(struct kvm_pic *pic, int irq, int irq_source_id, int level);
 void kvm_pic_clear_all(struct kvm_pic *pic, int irq_source_id);
 
diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index c91ee2927dd7..896abf9c1126 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -3513,6 +3513,8 @@ void kvm_mmu_free_roots(struct kvm *kvm, struct kvm_mmu *mmu,
 	LIST_HEAD(invalid_list);
 	bool free_active_root;
 
+	WARN_ON_ONCE(roots_to_free & ~KVM_MMU_ROOTS_ALL);
+
 	BUILD_BUG_ON(KVM_MMU_NUM_PREV_ROOTS >= BITS_PER_LONG);
 
 	/* Before acquiring the MMU lock, see if we need to do any real work. */
--