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[34.78.232.44]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-374b9859486sm7078112f8f.111.2024.09.01.22.27.15 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 01 Sep 2024 22:27:15 -0700 (PDT) Date: Mon, 2 Sep 2024 05:27:13 +0000 From: Sebastian Ene To: Marc Zyngier Cc: Vincent Donnefort , akpm@linux-foundation.org, alexghiti@rivosinc.com, ankita@nvidia.com, ardb@kernel.org, catalin.marinas@arm.com, christophe.leroy@csgroup.eu, james.morse@arm.com, mark.rutland@arm.com, oliver.upton@linux.dev, rananta@google.com, ryan.roberts@arm.com, shahuang@redhat.com, suzuki.poulose@arm.com, will@kernel.org, yuzenghui@huawei.com, kvmarm@lists.linux.dev, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, kernel-team@android.com Subject: Re: [PATCH v9 4/5] KVM: arm64: Register ptdump with debugfs on guest creation Message-ID: References: <20240827084549.45731-1-sebastianene@google.com> <20240827084549.45731-5-sebastianene@google.com> <865xriw161.wl-maz@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <865xriw161.wl-maz@kernel.org> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20240901_222719_652989_A78EF626 X-CRM114-Status: GOOD ( 48.12 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Fri, Aug 30, 2024 at 03:11:34PM +0100, Marc Zyngier wrote: > On Fri, 30 Aug 2024 11:24:53 +0100, > Vincent Donnefort wrote: > > > > Hi Seb, > > > > Thanks for the respin. > > > > On Tue, Aug 27, 2024 at 08:45:47AM +0000, Sebastian Ene wrote: > > > While arch/*/mem/ptdump handles the kernel pagetable dumping code, > > > introduce KVM/ptdump to show the guest stage-2 pagetables. The > > > separation is necessary because most of the definitions from the > > > stage-2 pagetable reside in the KVM path and we will be invoking > > > functionality specific to KVM. > > > > > > When a guest is created, register a new file entry under the guest > > > debugfs dir which allows userspace to show the contents of the guest > > > stage-2 pagetables when accessed. > > > > > > Signed-off-by: Sebastian Ene > > > > I only have some nits, otherwise: > > > > Reviewed-by: Vincent Donnefort > > > > > --- > > > arch/arm64/include/asm/kvm_host.h | 6 + > > > arch/arm64/kvm/Makefile | 1 + > > > arch/arm64/kvm/arm.c | 1 + > > > arch/arm64/kvm/ptdump.c | 247 ++++++++++++++++++++++++++++++ > > > 4 files changed, 255 insertions(+) > > > create mode 100644 arch/arm64/kvm/ptdump.c > > > > > > diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h > > > index a33f5996ca9f..4acd589f086b 100644 > > > --- a/arch/arm64/include/asm/kvm_host.h > > > +++ b/arch/arm64/include/asm/kvm_host.h > > > @@ -1473,4 +1473,10 @@ void kvm_set_vm_id_reg(struct kvm *kvm, u32 reg, u64 val); > > > (pa + pi + pa3) == 1; \ > > > }) > > > > > > +#ifdef CONFIG_PTDUMP_STAGE2_DEBUGFS > > > +void kvm_s2_ptdump_create_debugfs(struct kvm *kvm); > > > +#else > > > +static inline void kvm_s2_ptdump_create_debugfs(struct kvm *kvm) {} > > > +#endif /* CONFIG_PTDUMP_STAGE2_DEBUGFS */ > > > + > > > #endif /* __ARM64_KVM_HOST_H__ */ > > > diff --git a/arch/arm64/kvm/Makefile b/arch/arm64/kvm/Makefile > > > index 86a629aaf0a1..e4233b323a73 100644 > > > --- a/arch/arm64/kvm/Makefile > > > +++ b/arch/arm64/kvm/Makefile > > > @@ -27,6 +27,7 @@ kvm-y += arm.o mmu.o mmio.o psci.o hypercalls.o pvtime.o \ > > > > > > kvm-$(CONFIG_HW_PERF_EVENTS) += pmu-emul.o pmu.o > > > kvm-$(CONFIG_ARM64_PTR_AUTH) += pauth.o > > > +kvm-$(CONFIG_PTDUMP_STAGE2_DEBUGFS) += ptdump.o > > > > > > always-y := hyp_constants.h hyp-constants.s > > > > > > diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c > > > index 9bef7638342e..b9fd928d3477 100644 > > > --- a/arch/arm64/kvm/arm.c > > > +++ b/arch/arm64/kvm/arm.c > > > @@ -228,6 +228,7 @@ vm_fault_t kvm_arch_vcpu_fault(struct kvm_vcpu *vcpu, struct vm_fault *vmf) > > > void kvm_arch_create_vm_debugfs(struct kvm *kvm) > > > { > > > kvm_sys_regs_create_debugfs(kvm); > > > + kvm_s2_ptdump_create_debugfs(kvm); > > > } > > > > > > static void kvm_destroy_mpidr_data(struct kvm *kvm) > > > diff --git a/arch/arm64/kvm/ptdump.c b/arch/arm64/kvm/ptdump.c > > > new file mode 100644 > > > index 000000000000..e72a928d4445 > > > --- /dev/null > > > +++ b/arch/arm64/kvm/ptdump.c > > > @@ -0,0 +1,247 @@ > > > +// SPDX-License-Identifier: GPL-2.0-only > > > +/* > > > + * Debug helper used to dump the stage-2 pagetables of the system and their > > > + * associated permissions. > > > + * > > > + * Copyright (C) Google, 2024 > > > + * Author: Sebastian Ene > > > + */ > > > +#include > > > +#include > > > +#include > > > + > > > +#include > > > +#include > > > > nit: I believe you wanted to follow the alphabetical order, if that is the case, > > kvm_host.h then kvm_pgtable.h > > > > > +#include > > > + > > > + > > > > nit: don't think double empty are a rule, I would remove it. > > > > > +#define MARKERS_LEN (2) > > > > nit: The brackets are not necessary for MARKERS_LEN. > > > > > +#define KVM_PGTABLE_MAX_LEVELS (KVM_PGTABLE_LAST_LEVEL + 1) > > > + > > > +struct kvm_ptdump_guest_state { > > > + struct kvm *kvm; > > > + struct ptdump_pg_state parser_state; > > > + struct addr_marker ipa_marker[MARKERS_LEN]; > > > + struct ptdump_pg_level level[KVM_PGTABLE_MAX_LEVELS]; > > > + struct ptdump_range range[MARKERS_LEN]; > > > +}; > > > + > > > +static const struct ptdump_prot_bits stage2_pte_bits[] = { > > > + { > > > + .mask = PTE_VALID, > > > + .val = PTE_VALID, > > > + .set = " ", > > > + .clear = "F", > > > > This is effectively never used because an invalid PTE is 0 and note_page() won't > > print it. This probably can be removed? > > Yeah, I can't see how we are going to trigger that one given that > PTE_VALID must be set, and that we only print something if the bit is > clear. > > Seb? When (pte_prot & mask == val) we print .set (which is empty), otherwise we print .clear (This is from dump_prot). Invalid non-zero PTEs should be printed in this case. > > > > > > + }, { > > > + .mask = KVM_PTE_LEAF_ATTR_LO_S2_S2AP_R | PTE_VALID, > > > + .val = KVM_PTE_LEAF_ATTR_LO_S2_S2AP_R | PTE_VALID, > > > + .set = "R", > > > + .clear = " ", > > > + }, { > > > + .mask = KVM_PTE_LEAF_ATTR_LO_S2_S2AP_W | PTE_VALID, > > > + .val = KVM_PTE_LEAF_ATTR_LO_S2_S2AP_W | PTE_VALID, > > > + .set = "W", > > > + .clear = " ", > > > + }, { > > > + .mask = KVM_PTE_LEAF_ATTR_HI_S2_XN | PTE_VALID, > > > + .val = PTE_VALID, > > > + .set = " ", > > > + .clear = "X", > > > + }, { > > > + .mask = KVM_PTE_LEAF_ATTR_LO_S2_AF | PTE_VALID, > > > + .val = KVM_PTE_LEAF_ATTR_LO_S2_AF | PTE_VALID, > > > + .set = "AF", > > > + .clear = " ", > > > + }, { > > > + .mask = PTE_TABLE_BIT | PTE_VALID, > > > + .val = PTE_VALID, > > > + .set = "BLK", > > > + .clear = " ", > > > + }, > > > +}; > > > + > > > +static int kvm_ptdump_visitor(const struct kvm_pgtable_visit_ctx *ctx, > > > + enum kvm_pgtable_walk_flags visit) > > > +{ > > > + struct ptdump_pg_state *st = ctx->arg; > > > + struct ptdump_state *pt_st = &st->ptdump; > > > + > > > + note_page(pt_st, ctx->addr, ctx->level, ctx->old); > > > + > > > + return 0; > > > +} > > > + > > > +static int kvm_ptdump_build_levels(struct ptdump_pg_level *level, u32 start_lvl) > > > +{ > > > + u32 i; > > > + u64 mask; > > > + > > > + if (WARN_ON_ONCE(start_lvl >= KVM_PGTABLE_LAST_LEVEL)) > > > + return -EINVAL; > > > + > > > + mask = 0; > > > + for (i = 0; i < ARRAY_SIZE(stage2_pte_bits); i++) > > > + mask |= stage2_pte_bits[i].mask; > > > + > > > + for (i = start_lvl; i < KVM_PGTABLE_MAX_LEVELS; i++) { > > > + snprintf(level[i].name, sizeof(level[i].name), "%d", i); > > > > %u, i being unsigned. > > > > > + > > > + level[i].num = ARRAY_SIZE(stage2_pte_bits); > > > + level[i].bits = stage2_pte_bits; > > > + level[i].mask = mask; > > > + } > > > + > > > + return 0; > > > +} > > > + > > > +static struct kvm_ptdump_guest_state *kvm_ptdump_parser_create(struct kvm *kvm) > > > +{ > > > + struct kvm_ptdump_guest_state *st; > > > + struct kvm_s2_mmu *mmu = &kvm->arch.mmu; > > > + struct kvm_pgtable *pgtable = mmu->pgt; > > > + int ret; > > > + > > > + st = kzalloc(sizeof(struct kvm_ptdump_guest_state), GFP_KERNEL_ACCOUNT); > > > + if (!st) > > > + return ERR_PTR(-ENOMEM); > > > + > > > + ret = kvm_ptdump_build_levels(&st->level[0], pgtable->start_level); > > > + if (ret) { > > > + kfree(st); > > > + return ERR_PTR(ret); > > > + } > > > + > > > + st->ipa_marker[0].name = "Guest IPA"; > > > + st->ipa_marker[1].start_address = BIT(pgtable->ia_bits); > > > + st->range[0].end = BIT(pgtable->ia_bits); > > > + > > > + st->kvm = kvm; > > > + st->parser_state = (struct ptdump_pg_state) { > > > + .marker = &st->ipa_marker[0], > > > + .level = -1, > > > + .pg_level = &st->level[0], > > > + .ptdump.range = &st->range[0], > > > + .start_address = 0, > > > + }; > > > + > > > + return st; > > > +} > > > + > > > +static int kvm_ptdump_guest_show(struct seq_file *m, void *unused) > > > +{ > > > + int ret; > > > + struct kvm_ptdump_guest_state *st = m->private; > > > + struct kvm *kvm = st->kvm; > > > + struct kvm_s2_mmu *mmu = &kvm->arch.mmu; > > > + struct ptdump_pg_state *parser_state = &st->parser_state; > > > + struct kvm_pgtable_walker walker = (struct kvm_pgtable_walker) { > > > + .cb = kvm_ptdump_visitor, > > > + .arg = parser_state, > > > + .flags = KVM_PGTABLE_WALK_LEAF, > > > + }; > > > + > > > + parser_state->seq = m; > > > + > > > + write_lock(&kvm->mmu_lock); > > > + ret = kvm_pgtable_walk(mmu->pgt, 0, BIT(mmu->pgt->ia_bits), &walker); > > > + write_unlock(&kvm->mmu_lock); > > > + > > > + return ret; > > > +} > > > + > > > +static int kvm_ptdump_guest_open(struct inode *m, struct file *file) > > > +{ > > > + struct kvm *kvm = m->i_private; > > > + struct kvm_ptdump_guest_state *st; > > > + int ret; > > > + > > > + if (!kvm_get_kvm_safe(kvm)) > > > + return -ENOENT; > > > + > > > + st = kvm_ptdump_parser_create(kvm); > > > + if (IS_ERR(st)) { > > > + ret = PTR_ERR(st); > > > + goto free_with_kvm_ref; > > > + } > > > + > > > + ret = single_open(file, kvm_ptdump_guest_show, st); > > > + if (!ret) > > > + return 0; > > > + > > > + kfree(st); > > > +free_with_kvm_ref: > > > > nit: I believe kfree understands IS_ERR() so you could have a simple "err:" > > label covering all the error path. > > I couldn't find such handling in kfree(). Could you point be to it? > > > > > > + kvm_put_kvm(kvm); > > > + return ret; > > > +} > > > + > > > +static int kvm_ptdump_guest_close(struct inode *m, struct file *file) > > > +{ > > > + struct kvm *kvm = m->i_private; > > > + void *st = ((struct seq_file *)file->private_data)->private; > > > + > > > + kfree(st); > > > + kvm_put_kvm(kvm); > > > + > > > + return single_release(m, file); > > > +} > > > + > > > +static const struct file_operations kvm_ptdump_guest_fops = { > > > + .open = kvm_ptdump_guest_open, > > > + .read = seq_read, > > > + .llseek = seq_lseek, > > > + .release = kvm_ptdump_guest_close, > > > +}; > > > + > > > +static int kvm_pgtable_debugfs_show(struct seq_file *m, void *unused) > > > +{ > > > + const struct file *file = m->file; > > > + struct kvm_pgtable *pgtable = m->private; > > > + > > > + if (!strcmp(file_dentry(file)->d_iname, "ipa_range")) > > I really dislike this sort of construct, and I'd rather we pick the > correct callback by construction rather than relying on a string > comparison. See below for a suggestion. > Thanks for the feedback and for the suggestion. Let me try to re-write this as indicated. > > > + seq_printf(m, "%2u\n", pgtable->ia_bits); > > > + else if (!strcmp(file_dentry(file)->d_iname, "stage2_levels")) > > > + seq_printf(m, "%1d\n", KVM_PGTABLE_LAST_LEVEL - pgtable->start_level + 1); > > > > nit: KVM_PGTABLE_MAX_LEVELS - pgtable->start_level ? > > > > > + return 0; > > > +} > > > + > > > +static int kvm_pgtable_debugfs_open(struct inode *m, struct file *file) > > > +{ > > > + struct kvm *kvm = m->i_private; > > > + struct kvm_pgtable *pgtable; > > > + int ret; > > > + > > > + if (!kvm_get_kvm_safe(kvm)) > > > + return -ENOENT; > > > + > > > + pgtable = kvm->arch.mmu.pgt; > > > + > > > + ret = single_open(file, kvm_pgtable_debugfs_show, pgtable); > > > + if (ret < 0) > > > + kvm_put_kvm(kvm); > > > + return ret; > > > +} > > > + > > > +static int kvm_pgtable_debugfs_close(struct inode *m, struct file *file) > > > +{ > > > + struct kvm *kvm = m->i_private; > > > + > > > + kvm_put_kvm(kvm); > > > + return single_release(m, file); > > > +} > > > + > > > +static const struct file_operations kvm_pgtable_debugfs_fops = { > > > + .open = kvm_pgtable_debugfs_open, > > > + .read = seq_read, > > > + .llseek = seq_lseek, > > > + .release = kvm_pgtable_debugfs_close, > > > +}; > > > + > > > +void kvm_s2_ptdump_create_debugfs(struct kvm *kvm) > > > +{ > > > + debugfs_create_file("stage2_page_tables", 0400, kvm->debugfs_dentry, > > > + kvm, &kvm_ptdump_guest_fops); > > > + debugfs_create_file("ipa_range", 0400, kvm->debugfs_dentry, kvm, > > > + &kvm_pgtable_debugfs_fops); > > > + debugfs_create_file("stage2_levels", 0400, kvm->debugfs_dentry, > > > + kvm, &kvm_pgtable_debugfs_fops); > > > +} > > I'd expect something like this instead: > > diff --git a/arch/arm64/kvm/ptdump.c b/arch/arm64/kvm/ptdump.c > index e72a928d4445..c11ea355aa51 100644 > --- a/arch/arm64/kvm/ptdump.c > +++ b/arch/arm64/kvm/ptdump.c > @@ -192,19 +191,24 @@ static const struct file_operations kvm_ptdump_guest_fops = { > .release = kvm_ptdump_guest_close, > }; > > -static int kvm_pgtable_debugfs_show(struct seq_file *m, void *unused) > +static int kvm_pgtable_range_show(struct seq_file *m, void *unused) > +{ > + struct kvm_pgtable *pgtable = m->private; > + > + seq_printf(m, "%2u\n", pgtable->ia_bits); > + return 0; > +} > + > +static int kvm_pgtable_levels_show(struct seq_file *m, void *unused) > { > - const struct file *file = m->file; > struct kvm_pgtable *pgtable = m->private; > > - if (!strcmp(file_dentry(file)->d_iname, "ipa_range")) > - seq_printf(m, "%2u\n", pgtable->ia_bits); > - else if (!strcmp(file_dentry(file)->d_iname, "stage2_levels")) > - seq_printf(m, "%1d\n", KVM_PGTABLE_LAST_LEVEL - pgtable->start_level + 1); > + seq_printf(m, "%1d\n", KVM_PGTABLE_LAST_LEVEL - pgtable->start_level + 1); > return 0; > } > > -static int kvm_pgtable_debugfs_open(struct inode *m, struct file *file) > +static int kvm_pgtable_debugfs_open(struct inode *m, struct file *file, > + int (*show)(struct seq_file *, void *)) > { > struct kvm *kvm = m->i_private; > struct kvm_pgtable *pgtable; > @@ -215,12 +219,22 @@ static int kvm_pgtable_debugfs_open(struct inode *m, struct file *file) > > pgtable = kvm->arch.mmu.pgt; > > - ret = single_open(file, kvm_pgtable_debugfs_show, pgtable); > + ret = single_open(file, show, pgtable); > if (ret < 0) > kvm_put_kvm(kvm); > return ret; > } > > +static int kvm_pgtable_range_open(struct inode *m, struct file *file) > +{ > + return kvm_pgtable_debugfs_open(m, file, kvm_pgtable_range_show); > +} > + > +static int kvm_pgtable_levels_open(struct inode *m, struct file *file) > +{ > + return kvm_pgtable_debugfs_open(m, file, kvm_pgtable_levels_show); > +} > + > static int kvm_pgtable_debugfs_close(struct inode *m, struct file *file) > { > struct kvm *kvm = m->i_private; > @@ -229,8 +243,15 @@ static int kvm_pgtable_debugfs_close(struct inode *m, struct file *file) > return single_release(m, file); > } > > -static const struct file_operations kvm_pgtable_debugfs_fops = { > - .open = kvm_pgtable_debugfs_open, > +static const struct file_operations kvm_pgtable_range_fops = { > + .open = kvm_pgtable_range_open, > + .read = seq_read, > + .llseek = seq_lseek, > + .release = kvm_pgtable_debugfs_close, > +}; > + > +static const struct file_operations kvm_pgtable_levels_fops = { > + .open = kvm_pgtable_levels_open, > .read = seq_read, > .llseek = seq_lseek, > .release = kvm_pgtable_debugfs_close, > @@ -241,7 +262,7 @@ void kvm_s2_ptdump_create_debugfs(struct kvm *kvm) > debugfs_create_file("stage2_page_tables", 0400, kvm->debugfs_dentry, > kvm, &kvm_ptdump_guest_fops); > debugfs_create_file("ipa_range", 0400, kvm->debugfs_dentry, kvm, > - &kvm_pgtable_debugfs_fops); > + &kvm_pgtable_range_fops); > debugfs_create_file("stage2_levels", 0400, kvm->debugfs_dentry, > - kvm, &kvm_pgtable_debugfs_fops); > + kvm, &kvm_pgtable_levels_fops); > } > > > Thanks, > > M. > Thanks, Seb > -- > Without deviation from the norm, progress is not possible.