| Message ID | 20200601115957.1581250-4-peterx@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | KVM: Dirty ring interface | expand |
On Mon, Jun 01, 2020 at 07:59:46AM -0400, Peter Xu wrote: > Originally, we have three code paths that can dirty a page without > vcpu context for X86: > > - init_rmode_identity_map > - init_rmode_tss > - kvmgt_rw_gpa > > init_rmode_identity_map and init_rmode_tss will be setup on > destination VM no matter what (and the guest cannot even see them), so > it does not make sense to track them at all. > > To do this, allow __x86_set_memory_region() to return the userspace > address that just allocated to the caller. Then in both of the > functions we directly write to the userspace address instead of > calling kvm_write_*() APIs. > > Another trivial change is that we don't need to explicitly clear the > identity page table root in init_rmode_identity_map() because no > matter what we'll write to the whole page with 4M huge page entries. > > Suggested-by: Paolo Bonzini <pbonzini@redhat.com> > Signed-off-by: Peter Xu <peterx@redhat.com> > --- > arch/x86/include/asm/kvm_host.h | 3 +- > arch/x86/kvm/svm/avic.c | 11 +++-- > arch/x86/kvm/vmx/vmx.c | 84 ++++++++++++++++----------------- > arch/x86/kvm/x86.c | 44 +++++++++++++---- > 4 files changed, 86 insertions(+), 56 deletions(-) > > diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h > index 42a2d0d3984a..39477f8f3f2c 100644 > --- a/arch/x86/include/asm/kvm_host.h > +++ b/arch/x86/include/asm/kvm_host.h > @@ -1650,7 +1650,8 @@ void __kvm_request_immediate_exit(struct kvm_vcpu *vcpu); > > int kvm_is_in_guest(void); > > -int __x86_set_memory_region(struct kvm *kvm, int id, gpa_t gpa, u32 size); > +void __user *__x86_set_memory_region(struct kvm *kvm, int id, gpa_t gpa, > + u32 size); > bool kvm_vcpu_is_reset_bsp(struct kvm_vcpu *vcpu); > bool kvm_vcpu_is_bsp(struct kvm_vcpu *vcpu); > > diff --git a/arch/x86/kvm/svm/avic.c b/arch/x86/kvm/svm/avic.c > index e80daa98682f..86e9621ba026 100644 > --- a/arch/x86/kvm/svm/avic.c > +++ b/arch/x86/kvm/svm/avic.c > @@ -235,7 +235,9 @@ static u64 *avic_get_physical_id_entry(struct kvm_vcpu *vcpu, > */ > static int avic_update_access_page(struct kvm *kvm, bool activate) > { > - int ret = 0; > + void __user *ret; > + int r = 0; > + > > mutex_lock(&kvm->slots_lock); > /* > @@ -251,13 +253,16 @@ static int avic_update_access_page(struct kvm *kvm, bool activate) > APIC_ACCESS_PAGE_PRIVATE_MEMSLOT, > APIC_DEFAULT_PHYS_BASE, > activate ? PAGE_SIZE : 0); > - if (ret) > + if (IS_ERR(ret)) { > + r = PTR_ERR(ret); > goto out; > + } > + > > kvm->arch.apic_access_page_done = activate; > out: > mutex_unlock(&kvm->slots_lock); > - return ret; > + return r; > } > > static int avic_init_backing_page(struct kvm_vcpu *vcpu) > diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c > index c2c6335a998c..c44637e8e9d6 100644 > --- a/arch/x86/kvm/vmx/vmx.c > +++ b/arch/x86/kvm/vmx/vmx.c > @@ -3442,34 +3442,26 @@ static bool guest_state_valid(struct kvm_vcpu *vcpu) > return true; > } > > -static int init_rmode_tss(struct kvm *kvm) > +static int init_rmode_tss(struct kvm *kvm, void __user *ua) > { > - gfn_t fn; > - u16 data = 0; > - int idx, r; > + const void *zero_page = (const void *) __va(page_to_phys(ZERO_PAGE(0))); > + u16 data; > + int i, r; > + > + for (i = 0; i < 3; i++) { > + r = __copy_to_user(ua + PAGE_SIZE * i, zero_page, PAGE_SIZE); > + if (r) No need to capture the return in 'r'. > + return -EFAULT; > + } > > - idx = srcu_read_lock(&kvm->srcu); > - fn = to_kvm_vmx(kvm)->tss_addr >> PAGE_SHIFT; > - r = kvm_clear_guest_page(kvm, fn, 0, PAGE_SIZE); > - if (r < 0) > - goto out; > data = TSS_BASE_SIZE + TSS_REDIRECTION_SIZE; > - r = kvm_write_guest_page(kvm, fn++, &data, > - TSS_IOPB_BASE_OFFSET, sizeof(u16)); > - if (r < 0) > - goto out; > - r = kvm_clear_guest_page(kvm, fn++, 0, PAGE_SIZE); > - if (r < 0) > - goto out; > - r = kvm_clear_guest_page(kvm, fn, 0, PAGE_SIZE); > - if (r < 0) > - goto out; > + r = __copy_to_user(ua + TSS_IOPB_BASE_OFFSET, &data, sizeof(u16)); > + if (r) Same here. > + return -EFAULT; > + > data = ~0; > - r = kvm_write_guest_page(kvm, fn, &data, > - RMODE_TSS_SIZE - 2 * PAGE_SIZE - 1, > - sizeof(u8)); > -out: > - srcu_read_unlock(&kvm->srcu, idx); > + r = __copy_to_user(ua + RMODE_TSS_SIZE - 1, &data, sizeof(u8)); Not that it really matters, but this should match the behavior of the other __copy_to_user() calls, i.e. explicitly return -EFAULT. Or switch the others to return the result. The mixed usage is odd. > + > return r; > } > > @@ -3477,7 +3469,7 @@ static int init_rmode_identity_map(struct kvm *kvm) > { > struct kvm_vmx *kvm_vmx = to_kvm_vmx(kvm); > int i, r = 0; > - kvm_pfn_t identity_map_pfn; > + void __user *uaddr; > u32 tmp; > > /* Protect kvm_vmx->ept_identity_pagetable_done. */ > @@ -3488,24 +3480,25 @@ static int init_rmode_identity_map(struct kvm *kvm) > > if (!kvm_vmx->ept_identity_map_addr) > kvm_vmx->ept_identity_map_addr = VMX_EPT_IDENTITY_PAGETABLE_ADDR; > - identity_map_pfn = kvm_vmx->ept_identity_map_addr >> PAGE_SHIFT; > > - r = __x86_set_memory_region(kvm, IDENTITY_PAGETABLE_PRIVATE_MEMSLOT, > - kvm_vmx->ept_identity_map_addr, PAGE_SIZE); > - if (r < 0) > + uaddr = __x86_set_memory_region(kvm, > + IDENTITY_PAGETABLE_PRIVATE_MEMSLOT, > + kvm_vmx->ept_identity_map_addr, > + PAGE_SIZE); > + if (IS_ERR(uaddr)) { > + r = PTR_ERR(uaddr); > goto out; > + } > > - r = kvm_clear_guest_page(kvm, identity_map_pfn, 0, PAGE_SIZE); > - if (r < 0) > - goto out; > /* Set up identity-mapping pagetable for EPT in real mode */ > for (i = 0; i < PT32_ENT_PER_PAGE; i++) { > tmp = (i << 22) + (_PAGE_PRESENT | _PAGE_RW | _PAGE_USER | > _PAGE_ACCESSED | _PAGE_DIRTY | _PAGE_PSE); > - r = kvm_write_guest_page(kvm, identity_map_pfn, > - &tmp, i * sizeof(tmp), sizeof(tmp)); > - if (r < 0) > + r = __copy_to_user(uaddr + i * sizeof(tmp), &tmp, sizeof(tmp)); > + if (r) { > + r = -EFAULT; Another case where capturing the result is unnecessary. I don't have a preference as to whether the result of __copy_{to,from}_user() is returned directly or morphed to -EFAULT, but we should be consistent, especially within a single patch. > goto out; > + } > } > kvm_vmx->ept_identity_pagetable_done = true; > > @@ -3532,19 +3525,22 @@ static void seg_setup(int seg) > static int alloc_apic_access_page(struct kvm *kvm) > { > struct page *page; > - int r = 0; > + void __user *r; > + int ret = 0; > > mutex_lock(&kvm->slots_lock); > if (kvm->arch.apic_access_page_done) > goto out; > r = __x86_set_memory_region(kvm, APIC_ACCESS_PAGE_PRIVATE_MEMSLOT, > APIC_DEFAULT_PHYS_BASE, PAGE_SIZE); Naming the new 'void __user *hva' would yield a smaller differ and would probably help readers in the future. > - if (r) > + if (IS_ERR(r)) { > + ret = PTR_ERR(r); > goto out; > + } > > page = gfn_to_page(kvm, APIC_DEFAULT_PHYS_BASE >> PAGE_SHIFT); > if (is_error_page(page)) { > - r = -EFAULT; > + ret = -EFAULT; > goto out; > } > > @@ -3556,7 +3552,7 @@ static int alloc_apic_access_page(struct kvm *kvm) > kvm->arch.apic_access_page_done = true; > out: > mutex_unlock(&kvm->slots_lock); > - return r; > + return ret; > } > > int allocate_vpid(void) > @@ -4483,7 +4479,7 @@ static int vmx_interrupt_allowed(struct kvm_vcpu *vcpu) > > static int vmx_set_tss_addr(struct kvm *kvm, unsigned int addr) > { > - int ret; > + void __user *ret; > > if (enable_unrestricted_guest) > return 0; > @@ -4493,10 +4489,12 @@ static int vmx_set_tss_addr(struct kvm *kvm, unsigned int addr) > PAGE_SIZE * 3); > mutex_unlock(&kvm->slots_lock); > > - if (ret) > - return ret; > + if (IS_ERR(ret)) > + return PTR_ERR(ret); > + > to_kvm_vmx(kvm)->tss_addr = addr; > - return init_rmode_tss(kvm); > + > + return init_rmode_tss(kvm, ret); > } > > static int vmx_set_identity_map_addr(struct kvm *kvm, u64 ident_addr) > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > index ac7b0e6f4000..5c106ca948ed 100644 > --- a/arch/x86/kvm/x86.c > +++ b/arch/x86/kvm/x86.c > @@ -9826,7 +9826,32 @@ void kvm_arch_sync_events(struct kvm *kvm) > kvm_free_pit(kvm); > } > > -int __x86_set_memory_region(struct kvm *kvm, int id, gpa_t gpa, u32 size) > +#define ERR_PTR_USR(e) ((void __user *)ERR_PTR(e)) > + > +/** > + * __x86_set_memory_region: Setup KVM internal memory slot > + * > + * @kvm: the kvm pointer to the VM. > + * @id: the slot ID to setup. > + * @gpa: the GPA to install the slot (unused when @size == 0). > + * @size: the size of the slot. Set to zero to uninstall a slot. > + * > + * This function helps to setup a KVM internal memory slot. Specify > + * @size > 0 to install a new slot, while @size == 0 to uninstall a > + * slot. The return code can be one of the following: > + * > + * HVA: on success (uninstall will return a bogus HVA) > + * -errno: on error > + * > + * The caller should always use IS_ERR() to check the return value > + * before use. Note, the KVM internal memory slots are guaranteed to > + * remain valid and unchanged until the VM is destroyed, i.e., the > + * GPA->HVA translation will not change. However, the HVA is a user > + * address, i.e. its accessibility is not guaranteed, and must be > + * accessed via __copy_{to,from}_user(). > + */ > +void __user * __x86_set_memory_region(struct kvm *kvm, int id, gpa_t gpa, > + u32 size) > { > int i, r; > unsigned long hva, uninitialized_var(old_npages); > @@ -9835,12 +9860,12 @@ int __x86_set_memory_region(struct kvm *kvm, int id, gpa_t gpa, u32 size) > > /* Called with kvm->slots_lock held. */ > if (WARN_ON(id >= KVM_MEM_SLOTS_NUM)) > - return -EINVAL; > + return ERR_PTR_USR(-EINVAL); > > slot = id_to_memslot(slots, id); > if (size) { > if (slot && slot->npages) > - return -EEXIST; > + return ERR_PTR_USR(-EEXIST); > > /* > * MAP_SHARED to prevent internal slot pages from being moved > @@ -9849,17 +9874,18 @@ int __x86_set_memory_region(struct kvm *kvm, int id, gpa_t gpa, u32 size) > hva = vm_mmap(NULL, 0, size, PROT_READ | PROT_WRITE, > MAP_SHARED | MAP_ANONYMOUS, 0); > if (IS_ERR((void *)hva)) > - return PTR_ERR((void *)hva); > + return (void __user *)hva; > } else { > - if (!slot || !slot->npages) > - return 0; > - > /* > * Stuff a non-canonical value to catch use-after-delete. This > * ends up being 0 on 32-bit KVM, but there's no better > * alternative. > */ > hva = (unsigned long)(0xdeadull << 48); > + > + if (!slot || !slot->npages) > + return (void __user *)hva; My clever shenanigans got discarded, so this weirdness happily is gone. > + > old_npages = slot->npages; > } > > @@ -9873,13 +9899,13 @@ int __x86_set_memory_region(struct kvm *kvm, int id, gpa_t gpa, u32 size) > m.memory_size = size; > r = __kvm_set_memory_region(kvm, &m); > if (r < 0) > - return r; > + return ERR_PTR_USR(r); > } > > if (!size) > vm_munmap(hva, old_npages * PAGE_SIZE); > > - return 0; > + return (void __user *)hva; > } > EXPORT_SYMBOL_GPL(__x86_set_memory_region); > > -- > 2.26.2 >
On Thu, Jul 02, 2020 at 05:05:57PM -0700, Sean Christopherson wrote: > > /* Set up identity-mapping pagetable for EPT in real mode */ > > for (i = 0; i < PT32_ENT_PER_PAGE; i++) { > > tmp = (i << 22) + (_PAGE_PRESENT | _PAGE_RW | _PAGE_USER | > > _PAGE_ACCESSED | _PAGE_DIRTY | _PAGE_PSE); > > - r = kvm_write_guest_page(kvm, identity_map_pfn, > > - &tmp, i * sizeof(tmp), sizeof(tmp)); > > - if (r < 0) > > + r = __copy_to_user(uaddr + i * sizeof(tmp), &tmp, sizeof(tmp)); > > + if (r) { > > + r = -EFAULT; > > Another case where capturing the result is unnecessary. I don't have a > preference as to whether the result of __copy_{to,from}_user() is returned > directly or morphed to -EFAULT, but we should be consistent, especially > within a single patch. OK, I'll clean all these __copy_to_user() callers in the next version. > > > goto out; > > + } > > } > > kvm_vmx->ept_identity_pagetable_done = true; > > > > @@ -3532,19 +3525,22 @@ static void seg_setup(int seg) > > static int alloc_apic_access_page(struct kvm *kvm) > > { > > struct page *page; > > - int r = 0; > > + void __user *r; > > + int ret = 0; > > > > mutex_lock(&kvm->slots_lock); > > if (kvm->arch.apic_access_page_done) > > goto out; > > r = __x86_set_memory_region(kvm, APIC_ACCESS_PAGE_PRIVATE_MEMSLOT, > > APIC_DEFAULT_PHYS_BASE, PAGE_SIZE); > > Naming the new 'void __user *hva' would yield a smaller differ and would > probably help readers in the future. OK. > > } else { > > - if (!slot || !slot->npages) > > - return 0; > > - > > /* > > * Stuff a non-canonical value to catch use-after-delete. This > > * ends up being 0 on 32-bit KVM, but there's no better > > * alternative. > > */ > > hva = (unsigned long)(0xdeadull << 48); > > + > > + if (!slot || !slot->npages) > > + return (void __user *)hva; > > My clever shenanigans got discarded, so this weirdness happily is gone. I'll see what I get when I rebase. This series is easy to encounter conflicts during previous rebases for misterious reasons. I guess I'll just repost less frequently so I suffer less from rebase too. :) Thanks.
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h index 42a2d0d3984a..39477f8f3f2c 100644 --- a/arch/x86/include/asm/kvm_host.h +++ b/arch/x86/include/asm/kvm_host.h @@ -1650,7 +1650,8 @@ void __kvm_request_immediate_exit(struct kvm_vcpu *vcpu); int kvm_is_in_guest(void); -int __x86_set_memory_region(struct kvm *kvm, int id, gpa_t gpa, u32 size); +void __user *__x86_set_memory_region(struct kvm *kvm, int id, gpa_t gpa, + u32 size); bool kvm_vcpu_is_reset_bsp(struct kvm_vcpu *vcpu); bool kvm_vcpu_is_bsp(struct kvm_vcpu *vcpu); diff --git a/arch/x86/kvm/svm/avic.c b/arch/x86/kvm/svm/avic.c index e80daa98682f..86e9621ba026 100644 --- a/arch/x86/kvm/svm/avic.c +++ b/arch/x86/kvm/svm/avic.c @@ -235,7 +235,9 @@ static u64 *avic_get_physical_id_entry(struct kvm_vcpu *vcpu, */ static int avic_update_access_page(struct kvm *kvm, bool activate) { - int ret = 0; + void __user *ret; + int r = 0; + mutex_lock(&kvm->slots_lock); /* @@ -251,13 +253,16 @@ static int avic_update_access_page(struct kvm *kvm, bool activate) APIC_ACCESS_PAGE_PRIVATE_MEMSLOT, APIC_DEFAULT_PHYS_BASE, activate ? PAGE_SIZE : 0); - if (ret) + if (IS_ERR(ret)) { + r = PTR_ERR(ret); goto out; + } + kvm->arch.apic_access_page_done = activate; out: mutex_unlock(&kvm->slots_lock); - return ret; + return r; } static int avic_init_backing_page(struct kvm_vcpu *vcpu) diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c index c2c6335a998c..c44637e8e9d6 100644 --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -3442,34 +3442,26 @@ static bool guest_state_valid(struct kvm_vcpu *vcpu) return true; } -static int init_rmode_tss(struct kvm *kvm) +static int init_rmode_tss(struct kvm *kvm, void __user *ua) { - gfn_t fn; - u16 data = 0; - int idx, r; + const void *zero_page = (const void *) __va(page_to_phys(ZERO_PAGE(0))); + u16 data; + int i, r; + + for (i = 0; i < 3; i++) { + r = __copy_to_user(ua + PAGE_SIZE * i, zero_page, PAGE_SIZE); + if (r) + return -EFAULT; + } - idx = srcu_read_lock(&kvm->srcu); - fn = to_kvm_vmx(kvm)->tss_addr >> PAGE_SHIFT; - r = kvm_clear_guest_page(kvm, fn, 0, PAGE_SIZE); - if (r < 0) - goto out; data = TSS_BASE_SIZE + TSS_REDIRECTION_SIZE; - r = kvm_write_guest_page(kvm, fn++, &data, - TSS_IOPB_BASE_OFFSET, sizeof(u16)); - if (r < 0) - goto out; - r = kvm_clear_guest_page(kvm, fn++, 0, PAGE_SIZE); - if (r < 0) - goto out; - r = kvm_clear_guest_page(kvm, fn, 0, PAGE_SIZE); - if (r < 0) - goto out; + r = __copy_to_user(ua + TSS_IOPB_BASE_OFFSET, &data, sizeof(u16)); + if (r) + return -EFAULT; + data = ~0; - r = kvm_write_guest_page(kvm, fn, &data, - RMODE_TSS_SIZE - 2 * PAGE_SIZE - 1, - sizeof(u8)); -out: - srcu_read_unlock(&kvm->srcu, idx); + r = __copy_to_user(ua + RMODE_TSS_SIZE - 1, &data, sizeof(u8)); + return r; } @@ -3477,7 +3469,7 @@ static int init_rmode_identity_map(struct kvm *kvm) { struct kvm_vmx *kvm_vmx = to_kvm_vmx(kvm); int i, r = 0; - kvm_pfn_t identity_map_pfn; + void __user *uaddr; u32 tmp; /* Protect kvm_vmx->ept_identity_pagetable_done. */ @@ -3488,24 +3480,25 @@ static int init_rmode_identity_map(struct kvm *kvm) if (!kvm_vmx->ept_identity_map_addr) kvm_vmx->ept_identity_map_addr = VMX_EPT_IDENTITY_PAGETABLE_ADDR; - identity_map_pfn = kvm_vmx->ept_identity_map_addr >> PAGE_SHIFT; - r = __x86_set_memory_region(kvm, IDENTITY_PAGETABLE_PRIVATE_MEMSLOT, - kvm_vmx->ept_identity_map_addr, PAGE_SIZE); - if (r < 0) + uaddr = __x86_set_memory_region(kvm, + IDENTITY_PAGETABLE_PRIVATE_MEMSLOT, + kvm_vmx->ept_identity_map_addr, + PAGE_SIZE); + if (IS_ERR(uaddr)) { + r = PTR_ERR(uaddr); goto out; + } - r = kvm_clear_guest_page(kvm, identity_map_pfn, 0, PAGE_SIZE); - if (r < 0) - goto out; /* Set up identity-mapping pagetable for EPT in real mode */ for (i = 0; i < PT32_ENT_PER_PAGE; i++) { tmp = (i << 22) + (_PAGE_PRESENT | _PAGE_RW | _PAGE_USER | _PAGE_ACCESSED | _PAGE_DIRTY | _PAGE_PSE); - r = kvm_write_guest_page(kvm, identity_map_pfn, - &tmp, i * sizeof(tmp), sizeof(tmp)); - if (r < 0) + r = __copy_to_user(uaddr + i * sizeof(tmp), &tmp, sizeof(tmp)); + if (r) { + r = -EFAULT; goto out; + } } kvm_vmx->ept_identity_pagetable_done = true; @@ -3532,19 +3525,22 @@ static void seg_setup(int seg) static int alloc_apic_access_page(struct kvm *kvm) { struct page *page; - int r = 0; + void __user *r; + int ret = 0; mutex_lock(&kvm->slots_lock); if (kvm->arch.apic_access_page_done) goto out; r = __x86_set_memory_region(kvm, APIC_ACCESS_PAGE_PRIVATE_MEMSLOT, APIC_DEFAULT_PHYS_BASE, PAGE_SIZE); - if (r) + if (IS_ERR(r)) { + ret = PTR_ERR(r); goto out; + } page = gfn_to_page(kvm, APIC_DEFAULT_PHYS_BASE >> PAGE_SHIFT); if (is_error_page(page)) { - r = -EFAULT; + ret = -EFAULT; goto out; } @@ -3556,7 +3552,7 @@ static int alloc_apic_access_page(struct kvm *kvm) kvm->arch.apic_access_page_done = true; out: mutex_unlock(&kvm->slots_lock); - return r; + return ret; } int allocate_vpid(void) @@ -4483,7 +4479,7 @@ static int vmx_interrupt_allowed(struct kvm_vcpu *vcpu) static int vmx_set_tss_addr(struct kvm *kvm, unsigned int addr) { - int ret; + void __user *ret; if (enable_unrestricted_guest) return 0; @@ -4493,10 +4489,12 @@ static int vmx_set_tss_addr(struct kvm *kvm, unsigned int addr) PAGE_SIZE * 3); mutex_unlock(&kvm->slots_lock); - if (ret) - return ret; + if (IS_ERR(ret)) + return PTR_ERR(ret); + to_kvm_vmx(kvm)->tss_addr = addr; - return init_rmode_tss(kvm); + + return init_rmode_tss(kvm, ret); } static int vmx_set_identity_map_addr(struct kvm *kvm, u64 ident_addr) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index ac7b0e6f4000..5c106ca948ed 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -9826,7 +9826,32 @@ void kvm_arch_sync_events(struct kvm *kvm) kvm_free_pit(kvm); } -int __x86_set_memory_region(struct kvm *kvm, int id, gpa_t gpa, u32 size) +#define ERR_PTR_USR(e) ((void __user *)ERR_PTR(e)) + +/** + * __x86_set_memory_region: Setup KVM internal memory slot + * + * @kvm: the kvm pointer to the VM. + * @id: the slot ID to setup. + * @gpa: the GPA to install the slot (unused when @size == 0). + * @size: the size of the slot. Set to zero to uninstall a slot. + * + * This function helps to setup a KVM internal memory slot. Specify + * @size > 0 to install a new slot, while @size == 0 to uninstall a + * slot. The return code can be one of the following: + * + * HVA: on success (uninstall will return a bogus HVA) + * -errno: on error + * + * The caller should always use IS_ERR() to check the return value + * before use. Note, the KVM internal memory slots are guaranteed to + * remain valid and unchanged until the VM is destroyed, i.e., the + * GPA->HVA translation will not change. However, the HVA is a user + * address, i.e. its accessibility is not guaranteed, and must be + * accessed via __copy_{to,from}_user(). + */ +void __user * __x86_set_memory_region(struct kvm *kvm, int id, gpa_t gpa, + u32 size) { int i, r; unsigned long hva, uninitialized_var(old_npages); @@ -9835,12 +9860,12 @@ int __x86_set_memory_region(struct kvm *kvm, int id, gpa_t gpa, u32 size) /* Called with kvm->slots_lock held. */ if (WARN_ON(id >= KVM_MEM_SLOTS_NUM)) - return -EINVAL; + return ERR_PTR_USR(-EINVAL); slot = id_to_memslot(slots, id); if (size) { if (slot && slot->npages) - return -EEXIST; + return ERR_PTR_USR(-EEXIST); /* * MAP_SHARED to prevent internal slot pages from being moved @@ -9849,17 +9874,18 @@ int __x86_set_memory_region(struct kvm *kvm, int id, gpa_t gpa, u32 size) hva = vm_mmap(NULL, 0, size, PROT_READ | PROT_WRITE, MAP_SHARED | MAP_ANONYMOUS, 0); if (IS_ERR((void *)hva)) - return PTR_ERR((void *)hva); + return (void __user *)hva; } else { - if (!slot || !slot->npages) - return 0; - /* * Stuff a non-canonical value to catch use-after-delete. This * ends up being 0 on 32-bit KVM, but there's no better * alternative. */ hva = (unsigned long)(0xdeadull << 48); + + if (!slot || !slot->npages) + return (void __user *)hva; + old_npages = slot->npages; } @@ -9873,13 +9899,13 @@ int __x86_set_memory_region(struct kvm *kvm, int id, gpa_t gpa, u32 size) m.memory_size = size; r = __kvm_set_memory_region(kvm, &m); if (r < 0) - return r; + return ERR_PTR_USR(r); } if (!size) vm_munmap(hva, old_npages * PAGE_SIZE); - return 0; + return (void __user *)hva; } EXPORT_SYMBOL_GPL(__x86_set_memory_region);
Originally, we have three code paths that can dirty a page without vcpu context for X86: - init_rmode_identity_map - init_rmode_tss - kvmgt_rw_gpa init_rmode_identity_map and init_rmode_tss will be setup on destination VM no matter what (and the guest cannot even see them), so it does not make sense to track them at all. To do this, allow __x86_set_memory_region() to return the userspace address that just allocated to the caller. Then in both of the functions we directly write to the userspace address instead of calling kvm_write_*() APIs. Another trivial change is that we don't need to explicitly clear the identity page table root in init_rmode_identity_map() because no matter what we'll write to the whole page with 4M huge page entries. Suggested-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Peter Xu <peterx@redhat.com> --- arch/x86/include/asm/kvm_host.h | 3 +- arch/x86/kvm/svm/avic.c | 11 +++-- arch/x86/kvm/vmx/vmx.c | 84 ++++++++++++++++----------------- arch/x86/kvm/x86.c | 44 +++++++++++++---- 4 files changed, 86 insertions(+), 56 deletions(-)