Subject: Re: [PATCH v4 04/15] KVM: x86: Use generic async PF slot management
To:     Gavin Shan <gshan@redhat.com>, kvmarm@lists.cs.columbia.edu
Cc:     kvm@vger.kernel.org, maz@kernel.org, linux-kernel@vger.kernel.org,
        shan.gavin@gmail.com, Jonathan.Cameron@huawei.com,
        pbonzini@redhat.com, vkuznets@redhat.com, will@kernel.org
References: <20210815005947.83699-1-gshan@redhat.com>
 <20210815005947.83699-5-gshan@redhat.com>
From:   Eric Auger <eauger@redhat.com>
Message-ID: <a3b0e70a-eddd-9a85-2c9c-ba5446ac542b@redhat.com>
Date:   Wed, 10 Nov 2021 18:03:30 +0100
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Hi Gavin,

On 8/15/21 2:59 AM, Gavin Shan wrote:
> This uses the generic slot management mechanism for asynchronous
Now we have moved the hash table management in the generic code, Use
this latter ...
> page fault by enabling CONFIG_KVM_ASYNC_PF_SLOT because the private
> implementation is totally duplicate to the generic one.
> 
> The changes introduced by this is pretty mechanical and shouldn't
> cause any logical changes.
suggest: No functional change intended.
> 
> Signed-off-by: Gavin Shan <gshan@redhat.com>
> ---
>  arch/x86/include/asm/kvm_host.h |  2 -
>  arch/x86/kvm/Kconfig            |  1 +
>  arch/x86/kvm/mmu/mmu.c          |  2 +-
>  arch/x86/kvm/x86.c              | 86 +++------------------------------
>  4 files changed, 8 insertions(+), 83 deletions(-)
> 
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index 974cbfb1eefe..409c1e7137cd 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -810,7 +810,6 @@ struct kvm_vcpu_arch {
>  
>  	struct {
>  		bool halted;
> -		gfn_t gfns[ASYNC_PF_PER_VCPU];
>  		struct gfn_to_hva_cache data;
>  		u64 msr_en_val; /* MSR_KVM_ASYNC_PF_EN */
>  		u64 msr_int_val; /* MSR_KVM_ASYNC_PF_INT */
> @@ -1878,7 +1877,6 @@ void kvm_arch_async_page_ready(struct kvm_vcpu *vcpu,
>  			       struct kvm_async_pf *work);
>  void kvm_arch_async_page_present_queued(struct kvm_vcpu *vcpu);
>  bool kvm_arch_can_dequeue_async_page_present(struct kvm_vcpu *vcpu);
> -extern bool kvm_find_async_pf_gfn(struct kvm_vcpu *vcpu, gfn_t gfn);
>  
>  int kvm_skip_emulated_instruction(struct kvm_vcpu *vcpu);
>  int kvm_complete_insn_gp(struct kvm_vcpu *vcpu, int err);
> diff --git a/arch/x86/kvm/Kconfig b/arch/x86/kvm/Kconfig
> index ac69894eab88..53a6ef30b6ee 100644
> --- a/arch/x86/kvm/Kconfig
> +++ b/arch/x86/kvm/Kconfig
> @@ -32,6 +32,7 @@ config KVM
>  	select HAVE_KVM_IRQ_ROUTING
>  	select HAVE_KVM_EVENTFD
>  	select KVM_ASYNC_PF
> +	select KVM_ASYNC_PF_SLOT
>  	select USER_RETURN_NOTIFIER
>  	select KVM_MMIO
>  	select SCHED_INFO
> diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> index c4f4fa23320e..cd8aaa662ac2 100644
> --- a/arch/x86/kvm/mmu/mmu.c
> +++ b/arch/x86/kvm/mmu/mmu.c
> @@ -3799,7 +3799,7 @@ static bool try_async_pf(struct kvm_vcpu *vcpu, bool prefault, gfn_t gfn,
>  
>  	if (!prefault && kvm_can_do_async_pf(vcpu)) {
>  		trace_kvm_try_async_get_page(cr2_or_gpa, gfn);
> -		if (kvm_find_async_pf_gfn(vcpu, gfn)) {
> +		if (kvm_async_pf_find_slot(vcpu, gfn)) {
>  			trace_kvm_async_pf_doublefault(cr2_or_gpa, gfn);
>  			kvm_make_request(KVM_REQ_APF_HALT, vcpu);
>  			return true;
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 7f35d9324b99..a5f7d6122178 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -332,13 +332,6 @@ static struct kmem_cache *kvm_alloc_emulator_cache(void)
>  
>  static int emulator_fix_hypercall(struct x86_emulate_ctxt *ctxt);
>  
> -static inline void kvm_async_pf_hash_reset(struct kvm_vcpu *vcpu)
> -{
> -	int i;
> -	for (i = 0; i < ASYNC_PF_PER_VCPU; i++)
> -		vcpu->arch.apf.gfns[i] = ~0;
> -}
> -
>  static void kvm_on_user_return(struct user_return_notifier *urn)
>  {
>  	unsigned slot;
> @@ -854,7 +847,7 @@ void kvm_post_set_cr0(struct kvm_vcpu *vcpu, unsigned long old_cr0, unsigned lon
>  {
>  	if ((cr0 ^ old_cr0) & X86_CR0_PG) {
>  		kvm_clear_async_pf_completion_queue(vcpu);
> -		kvm_async_pf_hash_reset(vcpu);
> +		kvm_async_pf_reset_slot(vcpu);
>  	}
>  
>  	if ((cr0 ^ old_cr0) & KVM_MMU_CR0_ROLE_BITS)
> @@ -3118,7 +3111,7 @@ static int kvm_pv_enable_async_pf(struct kvm_vcpu *vcpu, u64 data)
>  
>  	if (!kvm_pv_async_pf_enabled(vcpu)) {
>  		kvm_clear_async_pf_completion_queue(vcpu);
> -		kvm_async_pf_hash_reset(vcpu);
> +		kvm_async_pf_reset_slot(vcpu);
>  		return 0;
>  	}
>  
> @@ -10704,7 +10697,7 @@ int kvm_arch_vcpu_create(struct kvm_vcpu *vcpu)
>  
>  	vcpu->arch.pat = MSR_IA32_CR_PAT_DEFAULT;
>  
> -	kvm_async_pf_hash_reset(vcpu);
> +	kvm_async_pf_reset_slot(vcpu);
>  	kvm_pmu_init(vcpu);
>  
>  	vcpu->arch.pending_external_vector = -1;
> @@ -10828,7 +10821,7 @@ void kvm_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event)
>  	kvmclock_reset(vcpu);
>  
>  	kvm_clear_async_pf_completion_queue(vcpu);
> -	kvm_async_pf_hash_reset(vcpu);
> +	kvm_async_pf_reset_slot(vcpu);
>  	vcpu->arch.apf.halted = false;
>  
>  	if (vcpu->arch.guest_fpu && kvm_mpx_supported()) {
> @@ -11737,73 +11730,6 @@ void kvm_arch_async_page_ready(struct kvm_vcpu *vcpu, struct kvm_async_pf *work)
>  	kvm_mmu_do_page_fault(vcpu, work->cr2_or_gpa, 0, true);
>  }
>  
> -static inline u32 kvm_async_pf_hash_fn(gfn_t gfn)
> -{
> -	BUILD_BUG_ON(!is_power_of_2(ASYNC_PF_PER_VCPU));
> -
> -	return hash_32(gfn & 0xffffffff, order_base_2(ASYNC_PF_PER_VCPU));
> -}
> -
> -static inline u32 kvm_async_pf_next_probe(u32 key)
> -{
> -	return (key + 1) & (ASYNC_PF_PER_VCPU - 1);
> -}
> -
> -static void kvm_add_async_pf_gfn(struct kvm_vcpu *vcpu, gfn_t gfn)
> -{
> -	u32 key = kvm_async_pf_hash_fn(gfn);
> -
> -	while (vcpu->arch.apf.gfns[key] != ~0)
> -		key = kvm_async_pf_next_probe(key);
> -
> -	vcpu->arch.apf.gfns[key] = gfn;
> -}
> -
> -static u32 kvm_async_pf_gfn_slot(struct kvm_vcpu *vcpu, gfn_t gfn)
> -{
> -	int i;
> -	u32 key = kvm_async_pf_hash_fn(gfn);
> -
> -	for (i = 0; i < ASYNC_PF_PER_VCPU &&
> -		     (vcpu->arch.apf.gfns[key] != gfn &&
> -		      vcpu->arch.apf.gfns[key] != ~0); i++)
> -		key = kvm_async_pf_next_probe(key);
> -
> -	return key;
> -}
> -
> -bool kvm_find_async_pf_gfn(struct kvm_vcpu *vcpu, gfn_t gfn)
> -{
> -	return vcpu->arch.apf.gfns[kvm_async_pf_gfn_slot(vcpu, gfn)] == gfn;
> -}
> -
> -static void kvm_del_async_pf_gfn(struct kvm_vcpu *vcpu, gfn_t gfn)
> -{
> -	u32 i, j, k;
> -
> -	i = j = kvm_async_pf_gfn_slot(vcpu, gfn);
> -
> -	if (WARN_ON_ONCE(vcpu->arch.apf.gfns[i] != gfn))
> -		return;
> -
> -	while (true) {
> -		vcpu->arch.apf.gfns[i] = ~0;
> -		do {
> -			j = kvm_async_pf_next_probe(j);
> -			if (vcpu->arch.apf.gfns[j] == ~0)
> -				return;
> -			k = kvm_async_pf_hash_fn(vcpu->arch.apf.gfns[j]);
> -			/*
> -			 * k lies cyclically in ]i,j]
> -			 * |    i.k.j |
> -			 * |....j i.k.| or  |.k..j i...|
> -			 */
> -		} while ((i <= j) ? (i < k && k <= j) : (i < k || k <= j));
> -		vcpu->arch.apf.gfns[i] = vcpu->arch.apf.gfns[j];
> -		i = j;
> -	}
> -}
> -
>  static inline int apf_put_user_notpresent(struct kvm_vcpu *vcpu)
>  {
>  	u32 reason = KVM_PV_REASON_PAGE_NOT_PRESENT;
> @@ -11867,7 +11793,7 @@ bool kvm_arch_async_page_not_present(struct kvm_vcpu *vcpu,
>  	struct x86_exception fault;
>  
>  	trace_kvm_async_pf_not_present(work->arch.token, work->cr2_or_gpa);
> -	kvm_add_async_pf_gfn(vcpu, work->arch.gfn);
> +	kvm_async_pf_add_slot(vcpu, work->arch.gfn);
>  
>  	if (kvm_can_deliver_async_pf(vcpu) &&
>  	    !apf_put_user_notpresent(vcpu)) {
> @@ -11904,7 +11830,7 @@ void kvm_arch_async_page_present(struct kvm_vcpu *vcpu,
>  	if (work->wakeup_all)
>  		work->arch.token = ~0; /* broadcast wakeup */
>  	else
> -		kvm_del_async_pf_gfn(vcpu, work->arch.gfn);
> +		kvm_async_pf_remove_slot(vcpu, work->arch.gfn);
>  	trace_kvm_async_pf_ready(work->arch.token, work->cr2_or_gpa);
>  
>  	if ((work->wakeup_all || work->notpresent_injected) &&
> 
Looks good to me

Eric