From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753429Ab3GIX3j (ORCPT ); Tue, 9 Jul 2013 19:29:39 -0400 Received: from mail-pb0-f52.google.com ([209.85.160.52]:51181 "EHLO mail-pb0-f52.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752375Ab3GIX3h (ORCPT ); Tue, 9 Jul 2013 19:29:37 -0400 Message-ID: <51DC9CDA.3070906@ozlabs.ru> Date: Wed, 10 Jul 2013 09:29:30 +1000 From: Alexey Kardashevskiy User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130514 Thunderbird/17.0.6 MIME-Version: 1.0 To: Alexander Graf CC: linuxppc-dev@lists.ozlabs.org, David Gibson , Benjamin Herrenschmidt , Paul Mackerras , Alex Williamson , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, kvm-ppc@vger.kernel.org Subject: Re: [PATCH 8/8] KVM: PPC: Add hugepage support for IOMMU in-kernel handling References: <1373123227-22969-1-git-send-email-aik@ozlabs.ru> <1373123227-22969-9-git-send-email-aik@ozlabs.ru> <51DC4923.5010501@suse.de> In-Reply-To: <51DC4923.5010501@suse.de> Content-Type: text/plain; charset=KOI8-R Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 07/10/2013 03:32 AM, Alexander Graf wrote: > On 07/06/2013 05:07 PM, Alexey Kardashevskiy wrote: >> This adds special support for huge pages (16MB). The reference >> counting cannot be easily done for such pages in real mode (when >> MMU is off) so we added a list of huge pages. It is populated in >> virtual mode and get_page is called just once per a huge page. >> Real mode handlers check if the requested page is huge and in the list, >> then no reference counting is done, otherwise an exit to virtual mode >> happens. The list is released at KVM exit. At the moment the fastest >> card available for tests uses up to 9 huge pages so walking through this >> list is not very expensive. However this can change and we may want >> to optimize this. >> >> Signed-off-by: Paul Mackerras >> Signed-off-by: Alexey Kardashevskiy >> >> --- >> >> Changes: >> 2013/06/27: >> * list of huge pages replaces with hashtable for better performance > > So the only thing your patch description really talks about is not true > anymore? > >> * spinlock removed from real mode and only protects insertion of new >> huge [ages descriptors into the hashtable >> >> 2013/06/05: >> * fixed compile error when CONFIG_IOMMU_API=n >> >> 2013/05/20: >> * the real mode handler now searches for a huge page by gpa (used to be pte) >> * the virtual mode handler prints warning if it is called twice for the same >> huge page as the real mode handler is expected to fail just once - when a >> huge >> page is not in the list yet. >> * the huge page is refcounted twice - when added to the hugepage list and >> when used in the virtual mode hcall handler (can be optimized but it will >> make the patch less nice). >> >> Signed-off-by: Alexey Kardashevskiy >> --- >> arch/powerpc/include/asm/kvm_host.h | 25 +++++++++ >> arch/powerpc/kernel/iommu.c | 6 ++- >> arch/powerpc/kvm/book3s_64_vio.c | 104 >> +++++++++++++++++++++++++++++++++--- >> arch/powerpc/kvm/book3s_64_vio_hv.c | 21 ++++++-- >> 4 files changed, 146 insertions(+), 10 deletions(-) >> >> diff --git a/arch/powerpc/include/asm/kvm_host.h >> b/arch/powerpc/include/asm/kvm_host.h >> index 53e61b2..a7508cf 100644 >> --- a/arch/powerpc/include/asm/kvm_host.h >> +++ b/arch/powerpc/include/asm/kvm_host.h >> @@ -30,6 +30,7 @@ >> #include >> #include >> #include >> +#include >> #include >> #include >> #include >> @@ -182,10 +183,34 @@ struct kvmppc_spapr_tce_table { >> u32 window_size; >> struct iommu_group *grp; /* used for IOMMU groups */ >> struct vfio_group *vfio_grp; /* used for IOMMU groups */ >> + DECLARE_HASHTABLE(hash_tab, ilog2(64)); /* used for IOMMU groups */ >> + spinlock_t hugepages_write_lock; /* used for IOMMU groups */ >> struct { struct { unsigned long put, indir, stuff; } rm, vm; } stat; >> struct page *pages[0]; >> }; >> >> +/* >> + * The KVM guest can be backed with 16MB pages. >> + * In this case, we cannot do page counting from the real mode >> + * as the compound pages are used - they are linked in a list >> + * with pointers as virtual addresses which are inaccessible >> + * in real mode. >> + * >> + * The code below keeps a 16MB pages list and uses page struct >> + * in real mode if it is already locked in RAM and inserted into >> + * the list or switches to the virtual mode where it can be >> + * handled in a usual manner. >> + */ >> +#define KVMPPC_SPAPR_HUGEPAGE_HASH(gpa) hash_32(gpa>> 24, 32) >> + >> +struct kvmppc_spapr_iommu_hugepage { >> + struct hlist_node hash_node; >> + unsigned long gpa; /* Guest physical address */ >> + unsigned long hpa; /* Host physical address */ >> + struct page *page; /* page struct of the very first subpage */ >> + unsigned long size; /* Huge page size (always 16MB at the moment) */ >> +}; >> + >> struct kvmppc_linear_info { >> void *base_virt; >> unsigned long base_pfn; >> diff --git a/arch/powerpc/kernel/iommu.c b/arch/powerpc/kernel/iommu.c >> index 51678ec..e0b6eca 100644 >> --- a/arch/powerpc/kernel/iommu.c >> +++ b/arch/powerpc/kernel/iommu.c >> @@ -999,7 +999,8 @@ int iommu_free_tces(struct iommu_table *tbl, unsigned >> long entry, >> if (!pg) { >> ret = -EAGAIN; >> } else if (PageCompound(pg)) { >> - ret = -EAGAIN; >> + /* Hugepages will be released at KVM exit */ >> + ret = 0; >> } else { >> if (oldtce& TCE_PCI_WRITE) >> SetPageDirty(pg); >> @@ -1009,6 +1010,9 @@ int iommu_free_tces(struct iommu_table *tbl, >> unsigned long entry, >> struct page *pg = pfn_to_page(oldtce>> PAGE_SHIFT); >> if (!pg) { >> ret = -EAGAIN; >> + } else if (PageCompound(pg)) { >> + /* Hugepages will be released at KVM exit */ >> + ret = 0; >> } else { >> if (oldtce& TCE_PCI_WRITE) >> SetPageDirty(pg); >> diff --git a/arch/powerpc/kvm/book3s_64_vio.c >> b/arch/powerpc/kvm/book3s_64_vio.c >> index 2b51f4a..c037219 100644 >> --- a/arch/powerpc/kvm/book3s_64_vio.c >> +++ b/arch/powerpc/kvm/book3s_64_vio.c >> @@ -46,6 +46,40 @@ >> >> #define ERROR_ADDR ((void *)~(unsigned long)0x0) >> >> +#ifdef CONFIG_IOMMU_API > > Can't you just make CONFIG_IOMMU_API mandatory in Kconfig? Sure I can. I can do anything. Why should I? Do I have to do that to get this accepted? I do not understand this comment. It has already been discussed how to enable this option. >> +static void kvmppc_iommu_hugepages_init(struct kvmppc_spapr_tce_table *tt) >> +{ >> + spin_lock_init(&tt->hugepages_write_lock); >> + hash_init(tt->hash_tab); >> +} >> + >> +static void kvmppc_iommu_hugepages_cleanup(struct kvmppc_spapr_tce_table >> *tt) >> +{ >> + int bkt; >> + struct kvmppc_spapr_iommu_hugepage *hp; >> + struct hlist_node *tmp; >> + >> + spin_lock(&tt->hugepages_write_lock); >> + hash_for_each_safe(tt->hash_tab, bkt, tmp, hp, hash_node) { >> + pr_debug("Release HP liobn=%llx #%u gpa=%lx hpa=%lx size=%ld\n", >> + tt->liobn, bkt, hp->gpa, hp->hpa, hp->size); > > trace point > >> + hlist_del_rcu(&hp->hash_node); >> + >> + put_page(hp->page); > > Don't you have to mark them dirty? get_user_pages_fast is called with writing==1. Does not it do the same? > >> + kfree(hp); >> + } >> + spin_unlock(&tt->hugepages_write_lock); >> +} >> +#else >> +static void kvmppc_iommu_hugepages_init(struct kvmppc_spapr_tce_table *tt) >> +{ >> +} >> + >> +static void kvmppc_iommu_hugepages_cleanup(struct kvmppc_spapr_tce_table >> *tt) >> +{ >> +} >> +#endif /* CONFIG_IOMMU_API */ >> + >> static long kvmppc_stt_npages(unsigned long window_size) >> { >> return ALIGN((window_size>> SPAPR_TCE_SHIFT) >> @@ -112,6 +146,7 @@ static void release_spapr_tce_table(struct >> kvmppc_spapr_tce_table *stt) >> >> mutex_lock(&kvm->lock); >> list_del(&stt->list); >> + kvmppc_iommu_hugepages_cleanup(stt); >> >> #ifdef CONFIG_IOMMU_API >> if (stt->grp) { >> @@ -200,6 +235,7 @@ long kvm_vm_ioctl_create_spapr_tce(struct kvm *kvm, >> kvm_get_kvm(kvm); >> >> mutex_lock(&kvm->lock); >> + kvmppc_iommu_hugepages_init(stt); >> list_add(&stt->list,&kvm->arch.spapr_tce_tables); >> >> mutex_unlock(&kvm->lock); >> @@ -283,6 +319,7 @@ long kvm_vm_ioctl_create_spapr_tce_iommu(struct kvm >> *kvm, >> >> kvm_get_kvm(kvm); >> mutex_lock(&kvm->lock); >> + kvmppc_iommu_hugepages_init(tt); >> list_add(&tt->list,&kvm->arch.spapr_tce_tables); >> mutex_unlock(&kvm->lock); >> >> @@ -307,10 +344,17 @@ long kvm_vm_ioctl_create_spapr_tce_iommu(struct kvm >> *kvm, >> >> /* Converts guest physical address to host virtual address */ >> static void __user *kvmppc_vm_gpa_to_hva_and_get(struct kvm_vcpu *vcpu, >> + struct kvmppc_spapr_tce_table *tt, >> unsigned long gpa, struct page **pg, unsigned long *hpa) >> { >> unsigned long hva, gfn = gpa>> PAGE_SHIFT; >> struct kvm_memory_slot *memslot; >> +#ifdef CONFIG_IOMMU_API >> + struct kvmppc_spapr_iommu_hugepage *hp; >> + unsigned key = KVMPPC_SPAPR_HUGEPAGE_HASH(gpa); >> + pte_t *ptep; >> + unsigned int shift = 0; >> +#endif >> >> memslot = search_memslots(kvm_memslots(vcpu->kvm), gfn); >> if (!memslot) >> @@ -325,6 +369,54 @@ static void __user >> *kvmppc_vm_gpa_to_hva_and_get(struct kvm_vcpu *vcpu, >> *hpa = __pa((unsigned long) page_address(*pg)) + >> (hva& ~PAGE_MASK); >> >> +#ifdef CONFIG_IOMMU_API > > This function is becoming incredibly large. Please split it up. Also please > document the code. Less than 100 lines is incredibly large? There are _many_ functions bigger than that. I do not really see the point in making a separate function which is going to be called only once. -- Alexey