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

[Gavin Shan <gshan@xxxxxxxxxx>]

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@xxxxxxxxxx>
> > ---
> >   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