Re: [PATCH v4 04/15] KVM: x86: Use generic async PF slot management

[Gavin Shan <gshan@redhat.com>]

Hi Eric,

On 11/11/21 1:03 AM, Eric Auger wrote:
> 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 ...

Ok.

>> 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.

Ok. The commit log will be improved accordingly in next respin.

>>
>> 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
> 

Ok.

Thanks,
Gavin