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Thu, 03 Oct 2019 01:35:51 +0000 Received: from b03ledav004.gho.boulder.ibm.com (b03ledav004.gho.boulder.ibm.com [9.17.130.235]) by b03cxnp08027.gho.boulder.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id x931ZnV461800724 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Thu, 3 Oct 2019 01:35:49 GMT Received: from b03ledav004.gho.boulder.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 435947805F; Thu, 3 Oct 2019 01:35:49 +0000 (GMT) Received: from b03ledav004.gho.boulder.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id BF7CB78060; Thu, 3 Oct 2019 01:35:36 +0000 (GMT) Received: from LeoBras.ibmuc.com (unknown [9.85.174.224]) by b03ledav004.gho.boulder.ibm.com (Postfix) with ESMTP; Thu, 3 Oct 2019 01:35:36 +0000 (GMT) From: Leonardo Bras To: linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, kvm-ppc@vger.kernel.org, linux-arch@vger.kernel.org, linux-mm@kvack.org Cc: Leonardo Bras , Benjamin Herrenschmidt , Paul Mackerras , Michael Ellerman , Arnd Bergmann , "Aneesh Kumar K.V" , Christophe Leroy , Nicholas Piggin , Andrew Morton , Mahesh Salgaonkar , Reza Arbab , Santosh Sivaraj , Balbir Singh , Thomas Gleixner , Greg Kroah-Hartman , Mike Rapoport , Allison Randal , Jason Gunthorpe , Dan Williams , Vlastimil Babka , Christoph Lameter , Logan Gunthorpe , Andrey Ryabinin , Alexey Dobriyan , Souptick Joarder , Mathieu Desnoyers , Ralph Campbell , Jesper Dangaard Brouer , Jann Horn , Davidlohr Bueso , "Peter Zijlstra (Intel)" , Ingo Molnar , Christian Brauner , Michal Hocko , Elena Reshetova , Roman Gushchin , Andrea Arcangeli , Al Viro , "Dmitry V. Levin" , =?utf-8?b?SsOpcsO0bWUgR2xpc3Nl?= , Song Liu , Bartlomiej Zolnierkiewicz , Ira Weiny , "Kirill A. Shutemov" , John Hubbard , Keith Busch Subject: [PATCH v5 09/11] powerpc/kvm/book3s_64: Applies counting method to monitor lockless pgtbl walks Date: Wed, 2 Oct 2019 22:33:23 -0300 Message-Id: <20191003013325.2614-10-leonardo@linux.ibm.com> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20191003013325.2614-1-leonardo@linux.ibm.com> References: <20191003013325.2614-1-leonardo@linux.ibm.com> MIME-Version: 1.0 X-TM-AS-GCONF: 00 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2019-10-03_01:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=459 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1908290000 definitions=main-1910030012 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Applies the counting-based method for monitoring all book3s_64-related functions that do lockless pagetable walks. Adds comments explaining that some lockless pagetable walks don't need protection due to guest pgd not being a target of THP collapse/split, or due to being called from Realmode + MSR_EE = 0. Given that some of these functions always are called in realmode, we use __{begin,end}_lockless_pgtbl_walk so we can decide when to disable interrupts. local_irq_{save,restore} is already inside {begin,end}_lockless_pgtbl_walk, so there is no need to repeat it here. Variable that saves the irq mask was renamed from flags to irq_mask so it doesn't lose meaning now it's not directly passed to local_irq_* functions. There are also a function that uses local_irq_{en,dis}able, so the return value of begin_lockless_pgtbl_walk() is ignored and we pass IRQS_ENABLED to end_lockless_pgtbl_walk() to mimic the effect of local_irq_enable(). Signed-off-by: Leonardo Bras --- arch/powerpc/kvm/book3s_64_mmu_hv.c | 6 ++--- arch/powerpc/kvm/book3s_64_mmu_radix.c | 34 +++++++++++++++++++++++--- arch/powerpc/kvm/book3s_64_vio_hv.c | 7 +++++- 3 files changed, 40 insertions(+), 7 deletions(-) diff --git a/arch/powerpc/kvm/book3s_64_mmu_hv.c b/arch/powerpc/kvm/book3s_64_mmu_hv.c index 9a75f0e1933b..d8f374c979f5 100644 --- a/arch/powerpc/kvm/book3s_64_mmu_hv.c +++ b/arch/powerpc/kvm/book3s_64_mmu_hv.c @@ -615,12 +615,12 @@ int kvmppc_book3s_hv_page_fault(struct kvm_run *run, struct kvm_vcpu *vcpu, /* if the guest wants write access, see if that is OK */ if (!writing && hpte_is_writable(r)) { pte_t *ptep, pte; - unsigned long flags; + unsigned long irq_mask; /* * We need to protect against page table destruction * hugepage split and collapse. */ - local_irq_save(flags); + irq_mask = begin_lockless_pgtbl_walk(kvm->mm); ptep = find_current_mm_pte(current->mm->pgd, hva, NULL, NULL); if (ptep) { @@ -628,7 +628,7 @@ int kvmppc_book3s_hv_page_fault(struct kvm_run *run, struct kvm_vcpu *vcpu, if (__pte_write(pte)) write_ok = 1; } - local_irq_restore(flags); + end_lockless_pgtbl_walk(kvm->mm, irq_mask); } } diff --git a/arch/powerpc/kvm/book3s_64_mmu_radix.c b/arch/powerpc/kvm/book3s_64_mmu_radix.c index 2d415c36a61d..8ba9742e2fc8 100644 --- a/arch/powerpc/kvm/book3s_64_mmu_radix.c +++ b/arch/powerpc/kvm/book3s_64_mmu_radix.c @@ -813,20 +813,20 @@ int kvmppc_book3s_instantiate_page(struct kvm_vcpu *vcpu, * Read the PTE from the process' radix tree and use that * so we get the shift and attribute bits. */ - local_irq_disable(); + begin_lockless_pgtbl_walk(kvm->mm); ptep = __find_linux_pte(vcpu->arch.pgdir, hva, NULL, &shift); /* * If the PTE disappeared temporarily due to a THP * collapse, just return and let the guest try again. */ if (!ptep) { - local_irq_enable(); + end_lockless_pgtbl_walk(kvm->mm, IRQS_ENABLED); if (page) put_page(page); return RESUME_GUEST; } pte = *ptep; - local_irq_enable(); + end_lockless_pgtbl_walk(kvm->mm, IRQS_ENABLED); /* If we're logging dirty pages, always map single pages */ large_enable = !(memslot->flags & KVM_MEM_LOG_DIRTY_PAGES); @@ -972,10 +972,16 @@ int kvm_unmap_radix(struct kvm *kvm, struct kvm_memory_slot *memslot, unsigned long gpa = gfn << PAGE_SHIFT; unsigned int shift; + /* + * We are walking the secondary (partition-scoped) page table here. + * We can do this without disabling irq because the Linux MM + * subsystem doesn't do THP splits and collapses on this tree. + */ ptep = __find_linux_pte(kvm->arch.pgtable, gpa, NULL, &shift); if (ptep && pte_present(*ptep)) kvmppc_unmap_pte(kvm, ptep, gpa, shift, memslot, kvm->arch.lpid); + return 0; } @@ -989,6 +995,11 @@ int kvm_age_radix(struct kvm *kvm, struct kvm_memory_slot *memslot, int ref = 0; unsigned long old, *rmapp; + /* + * We are walking the secondary (partition-scoped) page table here. + * We can do this without disabling irq because the Linux MM + * subsystem doesn't do THP splits and collapses on this tree. + */ ptep = __find_linux_pte(kvm->arch.pgtable, gpa, NULL, &shift); if (ptep && pte_present(*ptep) && pte_young(*ptep)) { old = kvmppc_radix_update_pte(kvm, ptep, _PAGE_ACCESSED, 0, @@ -1013,6 +1024,11 @@ int kvm_test_age_radix(struct kvm *kvm, struct kvm_memory_slot *memslot, unsigned int shift; int ref = 0; + /* + * We are walking the secondary (partition-scoped) page table here. + * We can do this without disabling irq because the Linux MM + * subsystem doesn't do THP splits and collapses on this tree. + */ ptep = __find_linux_pte(kvm->arch.pgtable, gpa, NULL, &shift); if (ptep && pte_present(*ptep) && pte_young(*ptep)) ref = 1; @@ -1030,6 +1046,11 @@ static int kvm_radix_test_clear_dirty(struct kvm *kvm, int ret = 0; unsigned long old, *rmapp; + /* + * We are walking the secondary (partition-scoped) page table here. + * We can do this without disabling irq because the Linux MM + * subsystem doesn't do THP splits and collapses on this tree. + */ ptep = __find_linux_pte(kvm->arch.pgtable, gpa, NULL, &shift); if (ptep && pte_present(*ptep) && pte_dirty(*ptep)) { ret = 1; @@ -1046,6 +1067,7 @@ static int kvm_radix_test_clear_dirty(struct kvm *kvm, 1UL << shift); spin_unlock(&kvm->mmu_lock); } + return ret; } @@ -1085,6 +1107,12 @@ void kvmppc_radix_flush_memslot(struct kvm *kvm, gpa = memslot->base_gfn << PAGE_SHIFT; spin_lock(&kvm->mmu_lock); for (n = memslot->npages; n; --n) { + /* + * We are walking the secondary (partition-scoped) page table + * here. + * We can do this without disabling irq because the Linux MM + * subsystem doesn't do THP splits and collapses on this tree. + */ ptep = __find_linux_pte(kvm->arch.pgtable, gpa, NULL, &shift); if (ptep && pte_present(*ptep)) kvmppc_unmap_pte(kvm, ptep, gpa, shift, memslot, diff --git a/arch/powerpc/kvm/book3s_64_vio_hv.c b/arch/powerpc/kvm/book3s_64_vio_hv.c index ab6eeb8e753e..0091c3d0ce89 100644 --- a/arch/powerpc/kvm/book3s_64_vio_hv.c +++ b/arch/powerpc/kvm/book3s_64_vio_hv.c @@ -441,6 +441,7 @@ long kvmppc_rm_h_put_tce(struct kvm_vcpu *vcpu, unsigned long liobn, static long kvmppc_rm_ua_to_hpa(struct kvm_vcpu *vcpu, unsigned long ua, unsigned long *phpa) { + struct kvm *kvm = vcpu->kvm; pte_t *ptep, pte; unsigned shift = 0; @@ -453,10 +454,14 @@ static long kvmppc_rm_ua_to_hpa(struct kvm_vcpu *vcpu, * to exit which will agains result in the below page table walk * to finish. */ + __begin_lockless_pgtbl_walk(kvm->mm, false); ptep = __find_linux_pte(vcpu->arch.pgdir, ua, NULL, &shift); - if (!ptep || !pte_present(*ptep)) + if (!ptep || !pte_present(*ptep)) { + __end_lockless_pgtbl_walk(kvm->mm, 0, false); return -ENXIO; + } pte = *ptep; + __end_lockless_pgtbl_walk(kvm->mm, 0, false); if (!shift) shift = PAGE_SHIFT;