Re: [PATCH RESEND v2 03/17] KVM: X86: Don't track dirty for KVM_SET_[TSS_ADDR|IDENTITY_MAP_ADDR]

Paolo Bonzini
2019-12-21T13:52:04Z

On 21/12/19 02:49, 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, a new parameter is added to kvm_[write|clear]_guest_page()
> to show whether we would like to track dirty bits for the operations.
> With that, pass in "false" to this new parameter for any guest memory
> write of the ioctls (KVM_SET_TSS_ADDR, KVM_SET_IDENTITY_MAP_ADDR).

We can also return the hva from x86_set_memory_region and
__x86_set_memory_region.

Paolo

> Signed-off-by: Peter Xu <peterx@redhat.com>
> ---
> arch/x86/kvm/vmx/vmx.c | 18 ++++++++++--------
> include/linux/kvm_host.h | 5 +++--
> virt/kvm/kvm_main.c | 25 ++++++++++++++++---------
> 3 files changed, 29 insertions(+), 19 deletions(-)
>
> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> index 04a8212704c1..1ff5a428f489 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -3452,24 +3452,24 @@ static int init_rmode_tss(struct kvm *kvm)
>
> 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);
> + r = kvm_clear_guest_page(kvm, fn, 0, PAGE_SIZE, false);
> 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));
> + TSS_IOPB_BASE_OFFSET, sizeof(u16), false);
> if (r < 0)
> goto out;
> - r = kvm_clear_guest_page(kvm, fn++, 0, PAGE_SIZE);
> + r = kvm_clear_guest_page(kvm, fn++, 0, PAGE_SIZE, false);
> if (r < 0)
> goto out;
> - r = kvm_clear_guest_page(kvm, fn, 0, PAGE_SIZE);
> + r = kvm_clear_guest_page(kvm, fn, 0, PAGE_SIZE, false);
> if (r < 0)
> goto out;
> data = ~0;
> r = kvm_write_guest_page(kvm, fn, &data,
> RMODE_TSS_SIZE - 2 * PAGE_SIZE - 1,
> - sizeof(u8));
> + sizeof(u8), false);
> out:
> srcu_read_unlock(&kvm->srcu, idx);
> return r;
> @@ -3498,7 +3498,7 @@ static int init_rmode_identity_map(struct kvm *kvm)
> goto out2;
>
> idx = srcu_read_lock(&kvm->srcu);
> - r = kvm_clear_guest_page(kvm, identity_map_pfn, 0, PAGE_SIZE);
> + r = kvm_clear_guest_page(kvm, identity_map_pfn, 0, PAGE_SIZE, false);
> if (r < 0)
> goto out;
> /* Set up identity-mapping pagetable for EPT in real mode */
> @@ -3506,7 +3506,8 @@ static int init_rmode_identity_map(struct kvm *kvm)
> 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));
> + &tmp, i * sizeof(tmp),
> + sizeof(tmp), false);
> if (r < 0)
> goto out;
> }
> @@ -7265,7 +7266,8 @@ static int vmx_write_pml_buffer(struct kvm_vcpu *vcpu)
> dst = vmcs12->pml_address + sizeof(u64) * vmcs12->guest_pml_index;
>
> if (kvm_write_guest_page(vcpu->kvm, gpa_to_gfn(dst), &gpa,
> - offset_in_page(dst), sizeof(gpa)))
> + offset_in_page(dst), sizeof(gpa),
> + false))
> return 0;
>
> vmcs12->guest_pml_index--;
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index 2ea1ea79befd..4e34cf97ca90 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -734,7 +734,7 @@ int kvm_read_guest(struct kvm *kvm, gpa_t gpa, void *data, unsigned long len);
> int kvm_read_guest_cached(struct kvm *kvm, struct gfn_to_hva_cache *ghc,
> void *data, unsigned long len);
> int kvm_write_guest_page(struct kvm *kvm, gfn_t gfn, const void *data,
> - int offset, int len);
> + int offset, int len, bool track_dirty);
> int kvm_write_guest(struct kvm *kvm, gpa_t gpa, const void *data,
> unsigned long len);
> int kvm_write_guest_cached(struct kvm *kvm, struct gfn_to_hva_cache *ghc,
> @@ -744,7 +744,8 @@ int kvm_write_guest_offset_cached(struct kvm *kvm, struct gfn_to_hva_cache *ghc,
> unsigned long len);
> int kvm_gfn_to_hva_cache_init(struct kvm *kvm, struct gfn_to_hva_cache *ghc,
> gpa_t gpa, unsigned long len);
> -int kvm_clear_guest_page(struct kvm *kvm, gfn_t gfn, int offset, int len);
> +int kvm_clear_guest_page(struct kvm *kvm, gfn_t gfn, int offset, int len,
> + bool track_dirty);
> int kvm_clear_guest(struct kvm *kvm, gpa_t gpa, unsigned long len);
> struct kvm_memory_slot *gfn_to_memslot(struct kvm *kvm, gfn_t gfn);
> bool kvm_is_visible_gfn(struct kvm *kvm, gfn_t gfn);
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index 7ee28af9eb48..b1047173d78e 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -2051,7 +2051,8 @@ int kvm_vcpu_read_guest_atomic(struct kvm_vcpu *vcpu, gpa_t gpa,
> EXPORT_SYMBOL_GPL(kvm_vcpu_read_guest_atomic);
>
> static int __kvm_write_guest_page(struct kvm_memory_slot *memslot, gfn_t gfn,
> - const void *data, int offset, int len)
> + const void *data, int offset, int len,
> + bool track_dirty)
> {
> int r;
> unsigned long addr;
> @@ -2062,16 +2063,19 @@ static int __kvm_write_guest_page(struct kvm_memory_slot *memslot, gfn_t gfn,
> r = __copy_to_user((void __user *)addr + offset, data, len);
> if (r)
> return -EFAULT;
> - mark_page_dirty_in_slot(memslot, gfn);
> + if (track_dirty)
> + mark_page_dirty_in_slot(memslot, gfn);
> return 0;
> }
>
> int kvm_write_guest_page(struct kvm *kvm, gfn_t gfn,
> - const void *data, int offset, int len)
> + const void *data, int offset, int len,
> + bool track_dirty)
> {
> struct kvm_memory_slot *slot = gfn_to_memslot(kvm, gfn);
>
> - return __kvm_write_guest_page(slot, gfn, data, offset, len);
> + return __kvm_write_guest_page(slot, gfn, data, offset, len,
> + track_dirty);
> }
> EXPORT_SYMBOL_GPL(kvm_write_guest_page);
>
> @@ -2080,7 +2084,8 @@ int kvm_vcpu_write_guest_page(struct kvm_vcpu *vcpu, gfn_t gfn,
> {
> struct kvm_memory_slot *slot = kvm_vcpu_gfn_to_memslot(vcpu, gfn);
>
> - return __kvm_write_guest_page(slot, gfn, data, offset, len);
> + return __kvm_write_guest_page(slot, gfn, data, offset,
> + len, true);
> }
> EXPORT_SYMBOL_GPL(kvm_vcpu_write_guest_page);
>
> @@ -2093,7 +2098,7 @@ int kvm_write_guest(struct kvm *kvm, gpa_t gpa, const void *data,
> int ret;
>
> while ((seg = next_segment(len, offset)) != 0) {
> - ret = kvm_write_guest_page(kvm, gfn, data, offset, seg);
> + ret = kvm_write_guest_page(kvm, gfn, data, offset, seg, true);
> if (ret < 0)
> return ret;
> offset = 0;
> @@ -2232,11 +2237,13 @@ int kvm_read_guest_cached(struct kvm *kvm, struct gfn_to_hva_cache *ghc,
> }
> EXPORT_SYMBOL_GPL(kvm_read_guest_cached);
>
> -int kvm_clear_guest_page(struct kvm *kvm, gfn_t gfn, int offset, int len)
> +int kvm_clear_guest_page(struct kvm *kvm, gfn_t gfn, int offset, int len,
> + bool track_dirty)
> {
> const void *zero_page = (const void *) __va(page_to_phys(ZERO_PAGE(0)));
>
> - return kvm_write_guest_page(kvm, gfn, zero_page, offset, len);
> + return kvm_write_guest_page(kvm, gfn, zero_page, offset, len,
> + track_dirty);
> }
> EXPORT_SYMBOL_GPL(kvm_clear_guest_page);
>
> @@ -2248,7 +2255,7 @@ int kvm_clear_guest(struct kvm *kvm, gpa_t gpa, unsigned long len)
> int ret;
>
> while ((seg = next_segment(len, offset)) != 0) {
> - ret = kvm_clear_guest_page(kvm, gfn, offset, seg);
> + ret = kvm_clear_guest_page(kvm, gfn, offset, seg, true);
> if (ret < 0)
> return ret;
> offset = 0;
>