From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alexey Kardashevskiy Date: Fri, 29 Mar 2019 05:43:26 +0000 Subject: [PATCH kernel v4] KVM: PPC: Allocate guest TCEs on demand too Message-Id: <20190329054326.48275-1-aik@ozlabs.ru> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: kvm-ppc@vger.kernel.org We already allocate hardware TCE tables in multiple levels and skip intermediate levels when we can, now it is a turn of the KVM TCE tables. Thankfully these are allocated already in 2 levels. This moves the table's last level allocation from the creating helper to kvmppc_tce_put() and kvm_spapr_tce_fault(). Since such allocation cannot be done in real mode, this creates a virtual mode version of kvmppc_tce_put() which handles allocations. This adds kvmppc_rm_ioba_validate() to do an additional test if the consequent kvmppc_tce_put() needs a page which has not been allocated; if this is the case, we bail out to virtual mode handlers. The allocations are protected by a new mutex as kvm->lock is not suitable for the task because the fault handler is called with the mmap_sem held but kvmhv_setup_mmu() locks kvm->lock and mmap_sem in the reverse order. Signed-off-by: Alexey Kardashevskiy --- Changes: v4: * redid locking * added a separate virtual mode's kvmppc_tce_put to avoid alloc_page() in otherwise realmode-only code v3: * fixed alignments in kvmppc_rm_ioba_validate v2: * added kvm mutex around alloc_page to prevent races; in both place we test the pointer, if NULL, then take a lock and check again so on a fast path we do not take a lock at all --- For NVLink2 pass through guests with 128TiB DMA windows and very fragmented system RAM the difference is gigabytes of RAM. Fun fact: after this patch the only remaining real+virtual function is kvmppc_find_table(). --- arch/powerpc/include/asm/kvm_host.h | 3 ++ arch/powerpc/include/asm/kvm_ppc.h | 2 - arch/powerpc/kvm/book3s_64_vio.c | 72 +++++++++++++++++++++++------ arch/powerpc/kvm/book3s_64_vio_hv.c | 66 +++++++++++++++++++------- 4 files changed, 110 insertions(+), 33 deletions(-) diff --git a/arch/powerpc/include/asm/kvm_host.h b/arch/powerpc/include/asm/kvm_host.h index e6b5bb012ccb..07cefa53222e 100644 --- a/arch/powerpc/include/asm/kvm_host.h +++ b/arch/powerpc/include/asm/kvm_host.h @@ -201,6 +201,8 @@ struct kvmppc_spapr_tce_iommu_table { struct kref kref; }; +#define TCES_PER_PAGE (PAGE_SIZE / sizeof(u64)) + struct kvmppc_spapr_tce_table { struct list_head list; struct kvm *kvm; @@ -210,6 +212,7 @@ struct kvmppc_spapr_tce_table { u64 offset; /* in pages */ u64 size; /* window size in pages */ struct list_head iommu_tables; + struct mutex alloc_lock; struct page *pages[0]; }; diff --git a/arch/powerpc/include/asm/kvm_ppc.h b/arch/powerpc/include/asm/kvm_ppc.h index e774a386980a..bde566dfd060 100644 --- a/arch/powerpc/include/asm/kvm_ppc.h +++ b/arch/powerpc/include/asm/kvm_ppc.h @@ -197,8 +197,6 @@ extern struct kvmppc_spapr_tce_table *kvmppc_find_table( (iommu_tce_check_ioba((stt)->page_shift, (stt)->offset, \ (stt)->size, (ioba), (npages)) ? \ H_PARAMETER : H_SUCCESS) -extern void kvmppc_tce_put(struct kvmppc_spapr_tce_table *tt, - unsigned long idx, unsigned long tce); extern long kvmppc_h_put_tce(struct kvm_vcpu *vcpu, unsigned long liobn, unsigned long ioba, unsigned long tce); extern long kvmppc_h_put_tce_indirect(struct kvm_vcpu *vcpu, diff --git a/arch/powerpc/kvm/book3s_64_vio.c b/arch/powerpc/kvm/book3s_64_vio.c index 5e3b62c491f8..66270e07449a 100644 --- a/arch/powerpc/kvm/book3s_64_vio.c +++ b/arch/powerpc/kvm/book3s_64_vio.c @@ -228,11 +228,33 @@ static void release_spapr_tce_table(struct rcu_head *head) unsigned long i, npages = kvmppc_tce_pages(stt->size); for (i = 0; i < npages; i++) - __free_page(stt->pages[i]); + if (stt->pages[i]) + __free_page(stt->pages[i]); kfree(stt); } +static struct page *kvm_spapr_get_tce_page(struct kvmppc_spapr_tce_table *stt, + unsigned long sttpage) +{ + struct page *page = stt->pages[sttpage]; + + if (page) + return page; + + mutex_lock(&stt->alloc_lock); + page = stt->pages[sttpage]; + if (!page) { + page = alloc_page(GFP_KERNEL | __GFP_ZERO); + WARN_ON_ONCE(!page); + if (page) + stt->pages[sttpage] = page; + } + mutex_unlock(&stt->alloc_lock); + + return page; +} + static vm_fault_t kvm_spapr_tce_fault(struct vm_fault *vmf) { struct kvmppc_spapr_tce_table *stt = vmf->vma->vm_file->private_data; @@ -241,7 +263,10 @@ static vm_fault_t kvm_spapr_tce_fault(struct vm_fault *vmf) if (vmf->pgoff >= kvmppc_tce_pages(stt->size)) return VM_FAULT_SIGBUS; - page = stt->pages[vmf->pgoff]; + page = kvm_spapr_get_tce_page(stt, vmf->pgoff); + if (!page) + return VM_FAULT_OOM; + get_page(page); vmf->page = page; return 0; @@ -296,7 +321,6 @@ long kvm_vm_ioctl_create_spapr_tce(struct kvm *kvm, struct kvmppc_spapr_tce_table *siter; unsigned long npages, size = args->size; int ret = -ENOMEM; - int i; if (!args->size || args->page_shift < 12 || args->page_shift > 34 || (args->offset + args->size > (ULLONG_MAX >> args->page_shift))) @@ -318,14 +342,9 @@ long kvm_vm_ioctl_create_spapr_tce(struct kvm *kvm, stt->offset = args->offset; stt->size = size; stt->kvm = kvm; + mutex_init(&stt->alloc_lock); INIT_LIST_HEAD_RCU(&stt->iommu_tables); - for (i = 0; i < npages; i++) { - stt->pages[i] = alloc_page(GFP_KERNEL | __GFP_ZERO); - if (!stt->pages[i]) - goto fail; - } - mutex_lock(&kvm->lock); /* Check this LIOBN hasn't been previously allocated */ @@ -352,11 +371,6 @@ long kvm_vm_ioctl_create_spapr_tce(struct kvm *kvm, if (ret >= 0) return ret; - fail: - for (i = 0; i < npages; i++) - if (stt->pages[i]) - __free_page(stt->pages[i]); - kfree(stt); fail_acct: kvmppc_account_memlimit(kvmppc_stt_pages(npages), false); @@ -413,6 +427,36 @@ static long kvmppc_tce_validate(struct kvmppc_spapr_tce_table *stt, return H_SUCCESS; } +/* + * Handles TCE requests for emulated devices. + * Puts guest TCE values to the table and expects user space to convert them. + * Cannot fail so kvmppc_tce_validate must be called before it. + */ +static void kvmppc_tce_put(struct kvmppc_spapr_tce_table *stt, + unsigned long idx, unsigned long tce) +{ + struct page *page; + u64 *tbl; + unsigned long sttpage; + + idx -= stt->offset; + sttpage = idx / TCES_PER_PAGE; + page = stt->pages[sttpage]; + + if (!page) { + /* We allow any TCE, not just with read|write permissions */ + if (!tce) + return; + + page = kvm_spapr_get_tce_page(stt, sttpage); + if (!page) + return; + } + tbl = page_to_virt(page); + + tbl[idx % TCES_PER_PAGE] = tce; +} + static void kvmppc_clear_tce(struct mm_struct *mm, struct iommu_table *tbl, unsigned long entry) { diff --git a/arch/powerpc/kvm/book3s_64_vio_hv.c b/arch/powerpc/kvm/book3s_64_vio_hv.c index 31e59748832a..484b47fa3960 100644 --- a/arch/powerpc/kvm/book3s_64_vio_hv.c +++ b/arch/powerpc/kvm/book3s_64_vio_hv.c @@ -66,8 +66,6 @@ #endif -#define TCES_PER_PAGE (PAGE_SIZE / sizeof(u64)) - /* * Finds a TCE table descriptor by LIOBN. * @@ -148,7 +146,6 @@ static long kvmppc_rm_tce_validate(struct kvmppc_spapr_tce_table *stt, return H_SUCCESS; } -#endif /* CONFIG_KVM_BOOK3S_HV_POSSIBLE */ /* Note on the use of page_address() in real mode, * @@ -180,13 +177,9 @@ static u64 *kvmppc_page_address(struct page *page) /* * Handles TCE requests for emulated devices. * Puts guest TCE values to the table and expects user space to convert them. - * Called in both real and virtual modes. - * Cannot fail so kvmppc_tce_validate must be called before it. - * - * WARNING: This will be called in real-mode on HV KVM and virtual - * mode on PR KVM + * Cannot fail so kvmppc_rm_tce_validate must be called before it. */ -void kvmppc_tce_put(struct kvmppc_spapr_tce_table *stt, +static void kvmppc_rm_tce_put(struct kvmppc_spapr_tce_table *stt, unsigned long idx, unsigned long tce) { struct page *page; @@ -194,13 +187,48 @@ void kvmppc_tce_put(struct kvmppc_spapr_tce_table *stt, idx -= stt->offset; page = stt->pages[idx / TCES_PER_PAGE]; + /* + * page must not be NULL in real mode, + * kvmppc_rm_ioba_validate() must have taken care of this. + */ + WARN_ON_ONCE_RM(!page); tbl = kvmppc_page_address(page); tbl[idx % TCES_PER_PAGE] = tce; } -EXPORT_SYMBOL_GPL(kvmppc_tce_put); -#ifdef CONFIG_KVM_BOOK3S_HV_POSSIBLE +/* + * TCEs pages are allocated in kvmppc_rm_tce_put() which won't be able to do so + * in real mode. + * Check if kvmppc_rm_tce_put() can succeed in real mode, i.e. a TCEs page is + * allocated or not required (when clearing a tce entry). + */ +static long kvmppc_rm_ioba_validate(struct kvmppc_spapr_tce_table *stt, + unsigned long ioba, unsigned long npages, bool clearing) +{ + unsigned long i, idx, sttpage, sttpages; + unsigned long ret = kvmppc_ioba_validate(stt, ioba, npages); + + if (ret) + return ret; + /* + * clearing=true says kvmppc_rm_tce_put won't be allocating pages + * for empty tces. + */ + if (clearing) + return H_SUCCESS; + + idx = (ioba >> stt->page_shift) - stt->offset; + sttpage = idx / TCES_PER_PAGE; + sttpages = _ALIGN_UP(idx % TCES_PER_PAGE + npages, TCES_PER_PAGE) / + TCES_PER_PAGE; + for (i = sttpage; i < sttpage + sttpages; ++i) + if (!stt->pages[i]) + return H_TOO_HARD; + + return H_SUCCESS; +} + static long iommu_tce_xchg_rm(struct mm_struct *mm, struct iommu_table *tbl, unsigned long entry, unsigned long *hpa, enum dma_data_direction *direction) @@ -378,7 +406,7 @@ long kvmppc_rm_h_put_tce(struct kvm_vcpu *vcpu, unsigned long liobn, if (!stt) return H_TOO_HARD; - ret = kvmppc_ioba_validate(stt, ioba, 1); + ret = kvmppc_rm_ioba_validate(stt, ioba, 1, tce = 0); if (ret != H_SUCCESS) return ret; @@ -406,7 +434,7 @@ long kvmppc_rm_h_put_tce(struct kvm_vcpu *vcpu, unsigned long liobn, } } - kvmppc_tce_put(stt, entry, tce); + kvmppc_rm_tce_put(stt, entry, tce); return H_SUCCESS; } @@ -477,7 +505,7 @@ long kvmppc_rm_h_put_tce_indirect(struct kvm_vcpu *vcpu, if (tce_list & (SZ_4K - 1)) return H_PARAMETER; - ret = kvmppc_ioba_validate(stt, ioba, npages); + ret = kvmppc_rm_ioba_validate(stt, ioba, npages, false); if (ret != H_SUCCESS) return ret; @@ -554,7 +582,7 @@ long kvmppc_rm_h_put_tce_indirect(struct kvm_vcpu *vcpu, } } - kvmppc_tce_put(stt, entry + i, tce); + kvmppc_rm_tce_put(stt, entry + i, tce); } unlock_exit: @@ -580,7 +608,7 @@ long kvmppc_rm_h_stuff_tce(struct kvm_vcpu *vcpu, if (!stt) return H_TOO_HARD; - ret = kvmppc_ioba_validate(stt, ioba, npages); + ret = kvmppc_rm_ioba_validate(stt, ioba, npages, tce_value = 0); if (ret != H_SUCCESS) return ret; @@ -607,7 +635,7 @@ long kvmppc_rm_h_stuff_tce(struct kvm_vcpu *vcpu, } for (i = 0; i < npages; ++i, ioba += (1ULL << stt->page_shift)) - kvmppc_tce_put(stt, ioba >> stt->page_shift, tce_value); + kvmppc_rm_tce_put(stt, ioba >> stt->page_shift, tce_value); return H_SUCCESS; } @@ -632,6 +660,10 @@ long kvmppc_h_get_tce(struct kvm_vcpu *vcpu, unsigned long liobn, idx = (ioba >> stt->page_shift) - stt->offset; page = stt->pages[idx / TCES_PER_PAGE]; + if (!page) { + vcpu->arch.regs.gpr[4] = 0; + return H_SUCCESS; + } tbl = (u64 *)page_address(page); vcpu->arch.regs.gpr[4] = tbl[idx % TCES_PER_PAGE]; -- 2.17.1