From: "Alex Bennée" <alex.bennee@linaro.org>
To: Chao Peng <chao.p.peng@linux.intel.com>
Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-mm@kvack.org, linux-fsdevel@vger.kernel.org,
linux-arch@vger.kernel.org, linux-api@vger.kernel.org,
linux-doc@vger.kernel.org, qemu-devel@nongnu.org,
Paolo Bonzini <pbonzini@redhat.com>,
Jonathan Corbet <corbet@lwn.net>,
Sean Christopherson <seanjc@google.com>,
Vitaly Kuznetsov <vkuznets@redhat.com>,
Wanpeng Li <wanpengli@tencent.com>,
Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
x86@kernel.org, "H . Peter Anvin" <hpa@zytor.com>,
Hugh Dickins <hughd@google.com>, Jeff Layton <jlayton@kernel.org>,
"J . Bruce Fields" <bfields@fieldses.org>,
Andrew Morton <akpm@linux-foundation.org>,
Shuah Khan <shuah@kernel.org>, Mike Rapoport <rppt@kernel.org>,
Steven Price <steven.price@arm.com>,
"Maciej S . Szmigiero" <mail@maciej.szmigiero.name>,
Vlastimil Babka <vbabka@suse.cz>,
Vishal Annapurve <vannapurve@google.com>,
Yu Zhang <yu.c.zhang@linux.intel.com>,
"Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>,
luto@kernel.org, jun.nakajima@intel.com, dave.hansen@intel.com,
ak@linux.intel.com, david@redhat.com, aarcange@redhat.com,
ddutile@redhat.com, dhildenb@redhat.com,
Quentin Perret <qperret@google.com>,
tabba@google.com, Michael Roth <michael.roth@amd.com>,
mhocko@suse.com, Muchun Song <songmuchun@bytedance.com>,
wei.w.wang@intel.com
Subject: Re: [PATCH v9 2/8] KVM: Extend the memslot to support fd-based private memory
Date: Mon, 14 Nov 2022 16:04:59 +0000 [thread overview]
Message-ID: <877czxbjf6.fsf@linaro.org> (raw)
In-Reply-To: <20221025151344.3784230-3-chao.p.peng@linux.intel.com>
Chao Peng <chao.p.peng@linux.intel.com> writes:
> In memory encryption usage, guest memory may be encrypted with special
> key and can be accessed only by the guest itself. We call such memory
> private memory. It's valueless and sometimes can cause problem to allow
> userspace to access guest private memory. This new KVM memslot extension
> allows guest private memory being provided though a restrictedmem
> backed file descriptor(fd) and userspace is restricted to access the
> bookmarked memory in the fd.
>
<snip>
> To make code maintenance easy, internally we use a binary compatible
> alias struct kvm_user_mem_region to handle both the normal and the
> '_ext' variants.
> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> index 0d5d4419139a..f1ae45c10c94 100644
> --- a/include/uapi/linux/kvm.h
> +++ b/include/uapi/linux/kvm.h
> @@ -103,6 +103,33 @@ struct kvm_userspace_memory_region {
> __u64 userspace_addr; /* start of the userspace allocated memory */
> };
>
> +struct kvm_userspace_memory_region_ext {
> + struct kvm_userspace_memory_region region;
> + __u64 restricted_offset;
> + __u32 restricted_fd;
> + __u32 pad1;
> + __u64 pad2[14];
> +};
> +
> +#ifdef __KERNEL__
> +/*
> + * kvm_user_mem_region is a kernel-only alias of kvm_userspace_memory_region_ext
> + * that "unpacks" kvm_userspace_memory_region so that KVM can directly access
> + * all fields from the top-level "extended" region.
> + */
> +struct kvm_user_mem_region {
> + __u32 slot;
> + __u32 flags;
> + __u64 guest_phys_addr;
> + __u64 memory_size;
> + __u64 userspace_addr;
> + __u64 restricted_offset;
> + __u32 restricted_fd;
> + __u32 pad1;
> + __u64 pad2[14];
> +};
> +#endif
I'm not sure I buy the argument this makes the code maintenance easier
because you now have multiple places to update if you extend the field.
Was this simply to avoid changing:
foo->slot to foo->region.slot
in the underlying code?
> +
> /*
> * The bit 0 ~ bit 15 of kvm_memory_region::flags are visible for userspace,
> * other bits are reserved for kvm internal use which are defined in
> @@ -110,6 +137,7 @@ struct kvm_userspace_memory_region {
> */
> #define KVM_MEM_LOG_DIRTY_PAGES (1UL << 0)
> #define KVM_MEM_READONLY (1UL << 1)
> +#define KVM_MEM_PRIVATE (1UL << 2)
>
> /* for KVM_IRQ_LINE */
> struct kvm_irq_level {
> @@ -1178,6 +1206,7 @@ struct kvm_ppc_resize_hpt {
> #define KVM_CAP_S390_ZPCI_OP 221
> #define KVM_CAP_S390_CPU_TOPOLOGY 222
> #define KVM_CAP_DIRTY_LOG_RING_ACQ_REL 223
> +#define KVM_CAP_PRIVATE_MEM 224
>
> #ifdef KVM_CAP_IRQ_ROUTING
>
> diff --git a/virt/kvm/Kconfig b/virt/kvm/Kconfig
> index 800f9470e36b..9ff164c7e0cc 100644
> --- a/virt/kvm/Kconfig
> +++ b/virt/kvm/Kconfig
> @@ -86,3 +86,6 @@ config KVM_XFER_TO_GUEST_WORK
>
> config HAVE_KVM_PM_NOTIFIER
> bool
> +
> +config HAVE_KVM_RESTRICTED_MEM
> + bool
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index e30f1b4ecfa5..8dace78a0278 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -1526,7 +1526,7 @@ static void kvm_replace_memslot(struct kvm *kvm,
> }
> }
>
> -static int check_memory_region_flags(const struct kvm_userspace_memory_region *mem)
> +static int check_memory_region_flags(const struct kvm_user_mem_region *mem)
> {
> u32 valid_flags = KVM_MEM_LOG_DIRTY_PAGES;
>
> @@ -1920,7 +1920,7 @@ static bool kvm_check_memslot_overlap(struct kvm_memslots *slots, int id,
> * Must be called holding kvm->slots_lock for write.
> */
> int __kvm_set_memory_region(struct kvm *kvm,
> - const struct kvm_userspace_memory_region *mem)
> + const struct kvm_user_mem_region *mem)
> {
> struct kvm_memory_slot *old, *new;
> struct kvm_memslots *slots;
> @@ -2024,7 +2024,7 @@ int __kvm_set_memory_region(struct kvm *kvm,
> EXPORT_SYMBOL_GPL(__kvm_set_memory_region);
>
> int kvm_set_memory_region(struct kvm *kvm,
> - const struct kvm_userspace_memory_region *mem)
> + const struct kvm_user_mem_region *mem)
> {
> int r;
>
> @@ -2036,7 +2036,7 @@ int kvm_set_memory_region(struct kvm *kvm,
> EXPORT_SYMBOL_GPL(kvm_set_memory_region);
>
> static int kvm_vm_ioctl_set_memory_region(struct kvm *kvm,
> - struct kvm_userspace_memory_region *mem)
> + struct kvm_user_mem_region *mem)
> {
> if ((u16)mem->slot >= KVM_USER_MEM_SLOTS)
> return -EINVAL;
> @@ -4627,6 +4627,33 @@ static int kvm_vm_ioctl_get_stats_fd(struct kvm *kvm)
> return fd;
> }
>
> +#define SANITY_CHECK_MEM_REGION_FIELD(field) \
> +do { \
> + BUILD_BUG_ON(offsetof(struct kvm_user_mem_region, field) != \
> + offsetof(struct kvm_userspace_memory_region, field)); \
> + BUILD_BUG_ON(sizeof_field(struct kvm_user_mem_region, field) != \
> + sizeof_field(struct kvm_userspace_memory_region, field)); \
> +} while (0)
> +
> +#define SANITY_CHECK_MEM_REGION_EXT_FIELD(field) \
> +do { \
> + BUILD_BUG_ON(offsetof(struct kvm_user_mem_region, field) != \
> + offsetof(struct kvm_userspace_memory_region_ext, field)); \
> + BUILD_BUG_ON(sizeof_field(struct kvm_user_mem_region, field) != \
> + sizeof_field(struct kvm_userspace_memory_region_ext, field)); \
> +} while (0)
> +
> +static void kvm_sanity_check_user_mem_region_alias(void)
> +{
> + SANITY_CHECK_MEM_REGION_FIELD(slot);
> + SANITY_CHECK_MEM_REGION_FIELD(flags);
> + SANITY_CHECK_MEM_REGION_FIELD(guest_phys_addr);
> + SANITY_CHECK_MEM_REGION_FIELD(memory_size);
> + SANITY_CHECK_MEM_REGION_FIELD(userspace_addr);
> + SANITY_CHECK_MEM_REGION_EXT_FIELD(restricted_offset);
> + SANITY_CHECK_MEM_REGION_EXT_FIELD(restricted_fd);
> +}
Do we have other examples in the kernel that jump these hoops?
> static long kvm_vm_ioctl(struct file *filp,
> unsigned int ioctl, unsigned long arg)
> {
> @@ -4650,14 +4677,20 @@ static long kvm_vm_ioctl(struct file *filp,
> break;
> }
> case KVM_SET_USER_MEMORY_REGION: {
> - struct kvm_userspace_memory_region kvm_userspace_mem;
> + struct kvm_user_mem_region mem;
> + unsigned long size = sizeof(struct kvm_userspace_memory_region);
> +
> + kvm_sanity_check_user_mem_region_alias();
>
> r = -EFAULT;
> - if (copy_from_user(&kvm_userspace_mem, argp,
> - sizeof(kvm_userspace_mem)))
> + if (copy_from_user(&mem, argp, size))
> + goto out;
> +
> + r = -EINVAL;
> + if (mem.flags & KVM_MEM_PRIVATE)
> goto out;
Hmm I can see in the later code you explicitly check for the
KVM_MEM_PRIVATE flag with:
if (get_user(flags, (u32 __user *)(argp + flags_offset)))
goto out;
if (flags & KVM_MEM_PRIVATE)
size = sizeof(struct kvm_userspace_memory_region_ext);
else
size = sizeof(struct kvm_userspace_memory_region);
I think it would make sense to bring that sanity checking forward into
this patch to avoid the validation logic working in two different ways
over the series.
>
> - r = kvm_vm_ioctl_set_memory_region(kvm, &kvm_userspace_mem);
> + r = kvm_vm_ioctl_set_memory_region(kvm, &mem);
> break;
> }
> case KVM_GET_DIRTY_LOG: {
--
Alex Bennée
next prev parent reply other threads:[~2022-11-14 16:16 UTC|newest]
Thread overview: 101+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-10-25 15:13 [PATCH v9 0/8] KVM: mm: fd-based approach for supporting KVM Chao Peng
2022-10-25 15:13 ` [PATCH v9 1/8] mm: Introduce memfd_restricted system call to create restricted user memory Chao Peng
2022-10-26 17:31 ` Isaku Yamahata
2022-10-28 6:12 ` Chao Peng
2022-10-27 10:20 ` Fuad Tabba
2022-10-31 17:47 ` Michael Roth
2022-11-01 11:37 ` Chao Peng
2022-11-01 15:19 ` Michael Roth
2022-11-01 19:30 ` Michael Roth
2022-11-02 14:53 ` Chao Peng
2022-11-02 21:19 ` Michael Roth
2022-11-14 14:02 ` Vlastimil Babka
2022-11-14 15:28 ` Kirill A. Shutemov
2022-11-14 22:16 ` Michael Roth
2022-11-15 9:48 ` Chao Peng
2022-11-14 22:16 ` Michael Roth
2022-11-02 21:14 ` Kirill A. Shutemov
2022-11-02 21:26 ` Michael Roth
2022-11-02 22:07 ` Michael Roth
2022-11-03 16:30 ` Kirill A. Shutemov
2022-11-29 0:06 ` Michael Roth
2022-11-29 11:21 ` Kirill A. Shutemov
2022-11-29 11:39 ` David Hildenbrand
2022-11-29 13:59 ` Chao Peng
2022-11-29 13:58 ` Chao Peng
2022-11-29 0:37 ` Michael Roth
2022-11-29 14:06 ` Chao Peng
2022-11-29 19:06 ` Michael Roth
2022-11-29 19:18 ` Michael Roth
2022-11-30 9:39 ` Chao Peng
2022-11-30 14:31 ` Michael Roth
2022-11-29 18:01 ` Vishal Annapurve
2022-12-02 2:16 ` Vishal Annapurve
2022-12-02 6:49 ` Chao Peng
2022-12-02 13:44 ` Kirill A . Shutemov
2022-10-25 15:13 ` [PATCH v9 2/8] KVM: Extend the memslot to support fd-based private memory Chao Peng
2022-10-27 10:25 ` Fuad Tabba
2022-10-28 7:04 ` Xiaoyao Li
2022-10-31 14:14 ` Chao Peng
2022-11-14 16:04 ` Alex Bennée [this message]
2022-11-15 9:29 ` Chao Peng
2022-10-25 15:13 ` [PATCH v9 3/8] KVM: Add KVM_EXIT_MEMORY_FAULT exit Chao Peng
2022-10-25 15:26 ` Peter Maydell
2022-10-25 16:17 ` Sean Christopherson
2022-10-27 10:27 ` Fuad Tabba
2022-10-28 6:14 ` Chao Peng
2022-11-15 16:56 ` Alex Bennée
2022-11-16 3:14 ` Chao Peng
2022-11-16 19:03 ` Alex Bennée
2022-11-17 13:45 ` Chao Peng
2022-11-17 15:08 ` Alex Bennée
2022-11-18 1:32 ` Chao Peng
2022-11-18 13:23 ` Alex Bennée
2022-11-18 15:59 ` Sean Christopherson
2022-11-22 9:50 ` Chao Peng
2022-11-23 18:02 ` Sean Christopherson
2022-11-16 18:15 ` Andy Lutomirski
2022-11-16 18:48 ` Sean Christopherson
2022-11-17 13:42 ` Chao Peng
2022-10-25 15:13 ` [PATCH v9 4/8] KVM: Use gfn instead of hva for mmu_notifier_retry Chao Peng
2022-10-27 10:29 ` Fuad Tabba
2022-11-04 2:28 ` Chao Peng
2022-11-04 22:29 ` Sean Christopherson
2022-11-08 7:16 ` Chao Peng
2022-11-10 17:53 ` Sean Christopherson
2022-11-10 20:06 ` Sean Christopherson
2022-11-11 8:27 ` Chao Peng
2022-10-25 15:13 ` [PATCH v9 5/8] KVM: Register/unregister the guest private memory regions Chao Peng
2022-10-27 10:31 ` Fuad Tabba
2022-11-03 23:04 ` Sean Christopherson
2022-11-04 8:28 ` Chao Peng
2022-11-04 21:19 ` Sean Christopherson
2022-11-08 8:24 ` Chao Peng
2022-11-08 1:35 ` Yuan Yao
2022-11-08 9:41 ` Chao Peng
2022-11-09 5:52 ` Yuan Yao
2022-11-16 22:24 ` Sean Christopherson
2022-11-17 13:20 ` Chao Peng
2022-10-25 15:13 ` [PATCH v9 6/8] KVM: Update lpage info when private/shared memory are mixed Chao Peng
2022-10-26 20:46 ` Isaku Yamahata
2022-10-28 6:38 ` Chao Peng
2022-11-08 12:08 ` Yuan Yao
2022-11-09 4:13 ` Chao Peng
2022-10-25 15:13 ` [PATCH v9 7/8] KVM: Handle page fault for private memory Chao Peng
2022-10-26 21:54 ` Isaku Yamahata
2022-10-28 6:55 ` Chao Peng
2022-11-01 0:02 ` Isaku Yamahata
2022-11-01 11:38 ` Chao Peng
2022-11-16 20:50 ` Ackerley Tng
2022-11-16 22:13 ` Sean Christopherson
2022-11-17 13:25 ` Chao Peng
2022-10-25 15:13 ` [PATCH v9 8/8] KVM: Enable and expose KVM_MEM_PRIVATE Chao Peng
2022-10-27 10:31 ` Fuad Tabba
2022-11-03 12:13 ` [PATCH v9 0/8] KVM: mm: fd-based approach for supporting KVM Vishal Annapurve
2022-11-08 0:41 ` Isaku Yamahata
2022-11-09 15:54 ` Kirill A. Shutemov
2022-11-15 14:36 ` Kirill A. Shutemov
2022-11-14 11:43 ` Alex Bennée
2022-11-16 5:00 ` Chao Peng
2022-11-16 9:40 ` Alex Bennée
2022-11-17 14:16 ` Chao Peng
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