[RFCv1 7/7] KVM: unmap guest memory using poisoned pages

From: Kirill A. Shutemov
Date: Fri Apr 02 2021 - 11:27:28 EST

TDX architecture aims to provide resiliency against confidentiality and
integrity attacks. Towards this goal, the TDX architecture helps enforce
the enabling of memory integrity for all TD-private memory.

The CPU memory controller computes the integrity check value (MAC) for
the data (cache line) during writes, and it stores the MAC with the
memory as meta-data. A 28-bit MAC is stored in the ECC bits.

Checking of memory integrity is performed during memory reads. If
integrity check fails, CPU poisones cache line.

On a subsequent consumption (read) of the poisoned data by software,
there are two possible scenarios:

- Core determines that the execution can continue and it treats
poison with exception semantics signaled as a #MCE

- Core determines execution cannot continue,and it does an unbreakable
shutdown

For more details, see Chapter 14 of Intel TDX Module EAS[1]

As some of integrity check failures may lead to system shutdown host
kernel must not allow any writes to TD-private memory. This requirment
clashes with KVM design: KVM expects the guest memory to be mapped into
host userspace (e.g. QEMU).

This patch aims to start discussion on how we can approach the issue.

For now I intentionally keep TDX out of picture here and try to find a
generic way to unmap KVM guest memory from host userspace. Hopefully, it
makes the patch more approachable. And anyone can try it out.

To the proposal:

Looking into existing codepaths I've discovered that we already have
semantics we want. That's PG_hwpoison'ed pages and SWP_HWPOISON swap
entries in page tables:

- If an application touches a page mapped with the SWP_HWPOISON, it will
get SIGBUS.

- GUP will fail with -EFAULT;

Access the poisoned memory via page cache doesn't match required
semantics right now, but it shouldn't be too hard to make it work:
access to poisoned dirty pages should give -EIO or -EHWPOISON.

My idea is that we can mark page as poisoned when we make it TD-private
and replace all PTEs that map the page with SWP_HWPOISON.

The patch is proof-of-concept and has known issues:

- Limited to swap-backed pages for now: anon or tmpfs/shmem

- No THP support

- Need a new FOLL_XXX flags to access such pages from KVM code.

- Page unpoisoning is not implemented. It proved to be more difficult
than I expected. I'm looking into solution.

- Poisoned pages must be tied to KVM instance and another KVM must not
be able to map the page into guest.

[1] https://software.intel.com/content/dam/develop/external/us/en/documents/intel-tdx-module-1eas.pdf

Not-signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
---
arch/x86/kvm/Kconfig | 1 +
arch/x86/kvm/cpuid.c | 3 +-
arch/x86/kvm/mmu/mmu.c | 15 ++-
arch/x86/kvm/mmu/paging_tmpl.h | 10 +-
arch/x86/kvm/x86.c | 6 ++
include/linux/kvm_host.h | 12 +++
include/linux/swapops.h | 20 ++++
include/uapi/linux/kvm_para.h | 1 +
mm/gup.c | 31 ++++---
mm/memory.c | 45 ++++++++-
mm/page_vma_mapped.c | 8 +-
mm/rmap.c | 2 +-
mm/shmem.c | 7 ++
virt/kvm/Kconfig | 3 +
virt/kvm/kvm_main.c | 164 +++++++++++++++++++++++++++++----
15 files changed, 290 insertions(+), 38 deletions(-)

diff --git a/arch/x86/kvm/Kconfig b/arch/x86/kvm/Kconfig
index 7ac592664c52..b7db1c455e7c 100644
--- a/arch/x86/kvm/Kconfig
+++ b/arch/x86/kvm/Kconfig
@@ -46,6 +46,7 @@ config KVM
select KVM_GENERIC_DIRTYLOG_READ_PROTECT
select KVM_VFIO
select SRCU
+ select HAVE_KVM_PROTECTED_MEMORY
help
Support hosting fully virtualized guest machines using hardware
virtualization extensions. You will need a fairly recent
diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index 38172ca627d3..1457692c1080 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -796,7 +796,8 @@ static inline int __do_cpuid_func(struct kvm_cpuid_array *array, u32 function)
(1 << KVM_FEATURE_PV_SEND_IPI) |
(1 << KVM_FEATURE_POLL_CONTROL) |
(1 << KVM_FEATURE_PV_SCHED_YIELD) |
- (1 << KVM_FEATURE_ASYNC_PF_INT);
+ (1 << KVM_FEATURE_ASYNC_PF_INT) |
+ (1 << KVM_FEATURE_MEM_PROTECTED);

if (sched_info_on())
entry->eax |= (1 << KVM_FEATURE_STEAL_TIME);
diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 6d16481aa29d..53a69c8c59f1 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -43,6 +43,7 @@
#include <linux/hash.h>
#include <linux/kern_levels.h>
#include <linux/kthread.h>
+#include <linux/rmap.h>

#include <asm/page.h>
#include <asm/memtype.h>
@@ -2758,7 +2759,8 @@ static void direct_pte_prefetch(struct kvm_vcpu *vcpu, u64 *sptep)
if (sp->role.level > PG_LEVEL_4K)
return;

- __direct_pte_prefetch(vcpu, sp, sptep);
+ if (!vcpu->kvm->mem_protected)
+ __direct_pte_prefetch(vcpu, sp, sptep);
}

static int host_pfn_mapping_level(struct kvm_vcpu *vcpu, gfn_t gfn,
@@ -3723,6 +3725,17 @@ static int direct_page_fault(struct kvm_vcpu *vcpu, gpa_t gpa, u32 error_code,
if (handle_abnormal_pfn(vcpu, is_tdp ? 0 : gpa, gfn, pfn, ACC_ALL, &r))
return r;

+ if (vcpu->kvm->mem_protected && unlikely(!is_noslot_pfn(pfn)) &&
+ !gfn_is_shared(vcpu->kvm, gfn)) {
+ struct page *page = pfn_to_page(pfn);
+ lock_page(page);
+ VM_BUG_ON_PAGE(!PageSwapBacked(page) && !PageReserved(page), page);
+ /* Recheck gfn_is_shared() under page lock */
+ if (!gfn_is_shared(vcpu->kvm, gfn) && !TestSetPageHWPoison(page))
+ try_to_unmap(page, TTU_IGNORE_MLOCK);
+ unlock_page(page);
+ }
+
r = RET_PF_RETRY;
spin_lock(&vcpu->kvm->mmu_lock);
if (mmu_notifier_retry(vcpu->kvm, mmu_seq))
diff --git a/arch/x86/kvm/mmu/paging_tmpl.h b/arch/x86/kvm/mmu/paging_tmpl.h
index 50e268eb8e1a..26b0494a1207 100644
--- a/arch/x86/kvm/mmu/paging_tmpl.h
+++ b/arch/x86/kvm/mmu/paging_tmpl.h
@@ -397,8 +397,14 @@ static int FNAME(walk_addr_generic)(struct guest_walker *walker,
goto error;

ptep_user = (pt_element_t __user *)((void *)host_addr + offset);
- if (unlikely(__get_user(pte, ptep_user)))
- goto error;
+ if (vcpu->kvm->mem_protected) {
+ if (copy_from_guest(vcpu->kvm, &pte, host_addr + offset,
+ sizeof(pte)))
+ goto error;
+ } else {
+ if (unlikely(__get_user(pte, ptep_user)))
+ goto error;
+ }
walker->ptep_user[walker->level - 1] = ptep_user;

trace_kvm_mmu_paging_element(pte, walker->level);
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 1b404e4d7dd8..f8183386abe7 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -8170,6 +8170,12 @@ int kvm_emulate_hypercall(struct kvm_vcpu *vcpu)
kvm_sched_yield(vcpu->kvm, a0);
ret = 0;
break;
+ case KVM_HC_ENABLE_MEM_PROTECTED:
+ ret = kvm_protect_memory(vcpu->kvm);
+ break;
+ case KVM_HC_MEM_SHARE:
+ ret = kvm_share_memory(vcpu->kvm, a0, a1);
+ break;
default:
ret = -KVM_ENOSYS;
break;
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index f3b1013fb22c..f941bcbefb79 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -436,6 +436,8 @@ static inline int kvm_arch_vcpu_memslots_id(struct kvm_vcpu *vcpu)
}
#endif

+#define KVM_NR_SHARED_RANGES 32
+
/*
* Note:
* memslots are not sorted by id anymore, please use id_to_memslot()
@@ -513,6 +515,9 @@ struct kvm {
pid_t userspace_pid;
unsigned int max_halt_poll_ns;
u32 dirty_ring_size;
+ bool mem_protected;
+ int nr_shared_ranges;
+ struct range shared_ranges[KVM_NR_SHARED_RANGES];
};

#define kvm_err(fmt, ...) \
@@ -709,6 +714,10 @@ void kvm_arch_flush_shadow_all(struct kvm *kvm);
void kvm_arch_flush_shadow_memslot(struct kvm *kvm,
struct kvm_memory_slot *slot);

+int kvm_protect_memory(struct kvm *kvm);
+int kvm_share_memory(struct kvm *kvm, unsigned long gfn, unsigned long npages);
+bool gfn_is_shared(struct kvm *kvm, unsigned long gfn);
+
int gfn_to_page_many_atomic(struct kvm_memory_slot *slot, gfn_t gfn,
struct page **pages, int nr_pages);

@@ -718,6 +727,9 @@ unsigned long gfn_to_hva_prot(struct kvm *kvm, gfn_t gfn, bool *writable);
unsigned long gfn_to_hva_memslot(struct kvm_memory_slot *slot, gfn_t gfn);
unsigned long gfn_to_hva_memslot_prot(struct kvm_memory_slot *slot, gfn_t gfn,
bool *writable);
+int copy_from_guest(struct kvm *kvm, void *data, unsigned long hva, int len);
+int copy_to_guest(struct kvm *kvm, unsigned long hva, const void *data, int len);
+
void kvm_release_page_clean(struct page *page);
void kvm_release_page_dirty(struct page *page);
void kvm_set_page_accessed(struct page *page);
diff --git a/include/linux/swapops.h b/include/linux/swapops.h
index d9b7c9132c2f..520589b12fb3 100644
--- a/include/linux/swapops.h
+++ b/include/linux/swapops.h
@@ -323,6 +323,16 @@ static inline int is_hwpoison_entry(swp_entry_t entry)
return swp_type(entry) == SWP_HWPOISON;
}

+static inline unsigned long hwpoison_entry_to_pfn(swp_entry_t entry)
+{
+ return swp_offset(entry);
+}
+
+static inline struct page *hwpoison_entry_to_page(swp_entry_t entry)
+{
+ return pfn_to_page(hwpoison_entry_to_pfn(entry));
+}
+
static inline void num_poisoned_pages_inc(void)
{
atomic_long_inc(&num_poisoned_pages);
@@ -345,6 +355,16 @@ static inline int is_hwpoison_entry(swp_entry_t swp)
return 0;
}

+static inline unsigned long hwpoison_entry_to_pfn(swp_entry_t entry)
+{
+ return 0;
+}
+
+static inline struct page *hwpoison_entry_to_page(swp_entry_t entry)
+{
+ return NULL;
+}
+
static inline void num_poisoned_pages_inc(void)
{
}
diff --git a/include/uapi/linux/kvm_para.h b/include/uapi/linux/kvm_para.h
index 09d36683ee0a..743e621111f0 100644
--- a/include/uapi/linux/kvm_para.h
+++ b/include/uapi/linux/kvm_para.h
@@ -17,6 +17,7 @@
#define KVM_E2BIG E2BIG
#define KVM_EPERM EPERM
#define KVM_EOPNOTSUPP 95
+#define KVM_EINTR EINTR

#define KVM_HC_VAPIC_POLL_IRQ 1
#define KVM_HC_MMU_OP 2
diff --git a/mm/gup.c b/mm/gup.c
index e4c224cd9661..ce4fdf213455 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -384,22 +384,31 @@ static struct page *follow_page_pte(struct vm_area_struct *vma,
ptep = pte_offset_map_lock(mm, pmd, address, &ptl);
pte = *ptep;
if (!pte_present(pte)) {
- swp_entry_t entry;
+ swp_entry_t entry = pte_to_swp_entry(pte);
+
+ if (pte_none(pte))
+ goto no_page;
+
/*
* KSM's break_ksm() relies upon recognizing a ksm page
* even while it is being migrated, so for that case we
* need migration_entry_wait().
*/
- if (likely(!(flags & FOLL_MIGRATION)))
- goto no_page;
- if (pte_none(pte))
- goto no_page;
- entry = pte_to_swp_entry(pte);
- if (!is_migration_entry(entry))
- goto no_page;
- pte_unmap_unlock(ptep, ptl);
- migration_entry_wait(mm, pmd, address);
- goto retry;
+ if (is_migration_entry(entry) && (flags & FOLL_MIGRATION)) {
+ pte_unmap_unlock(ptep, ptl);
+ migration_entry_wait(mm, pmd, address);
+ goto retry;
+ }
+
+ if (is_hwpoison_entry(entry)) {
+ page = hwpoison_entry_to_page(entry);
+ if (PageHWPoison(page) /* && (flags & FOLL_ALLOW_POISONED) */) {
+ get_page(page);
+ goto out;
+ }
+ }
+
+ goto no_page;
}
if ((flags & FOLL_NUMA) && pte_protnone(pte))
goto no_page;
diff --git a/mm/memory.c b/mm/memory.c
index feff48e1465a..524dce15a087 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -767,6 +767,9 @@ copy_nonpresent_pte(struct mm_struct *dst_mm, struct mm_struct *src_mm,
pte = pte_swp_mkuffd_wp(pte);
set_pte_at(src_mm, addr, src_pte, pte);
}
+ } else if (is_hwpoison_entry(entry)) {
+ page = hwpoison_entry_to_page(entry);
+ get_page(page);
}
set_pte_at(dst_mm, addr, dst_pte, pte);
return 0;
@@ -1305,6 +1308,9 @@ static unsigned long zap_pte_range(struct mmu_gather *tlb,

page = migration_entry_to_page(entry);
rss[mm_counter(page)]--;
+
+ } else if (is_hwpoison_entry(entry)) {
+ put_page(hwpoison_entry_to_page(entry));
}
if (unlikely(!free_swap_and_cache(entry)))
print_bad_pte(vma, addr, ptent, NULL);
@@ -3274,7 +3280,43 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
vmf->page = device_private_entry_to_page(entry);
ret = vmf->page->pgmap->ops->migrate_to_ram(vmf);
} else if (is_hwpoison_entry(entry)) {
- ret = VM_FAULT_HWPOISON;
+ page = hwpoison_entry_to_page(entry);
+
+ locked = lock_page_or_retry(page, vma->vm_mm, vmf->flags);
+ if (!locked) {
+ ret = VM_FAULT_RETRY;
+ goto out;
+ }
+
+ vmf->pte = pte_offset_map_lock(vma->vm_mm, vmf->pmd,
+ vmf->address, &vmf->ptl);
+
+ if (unlikely(!pte_same(*vmf->pte, vmf->orig_pte))) {
+ ret = 0;
+ } else if (PageHWPoison(page)) {
+ ret = VM_FAULT_HWPOISON;
+ } else {
+ /*
+ * The page is unpoisoned. Replace hwpoison
+ * entry with a present PTE.
+ */
+
+ inc_mm_counter(vma->vm_mm, mm_counter(page));
+ pte = mk_pte(page, vma->vm_page_prot);
+
+ if (PageAnon(page)) {
+ page_add_anon_rmap(page, vma,
+ vmf->address, false);
+ } else {
+ page_add_file_rmap(page, false);
+ }
+
+ set_pte_at(vma->vm_mm, vmf->address,
+ vmf->pte, pte);
+ }
+
+ pte_unmap_unlock(vmf->pte, vmf->ptl);
+ unlock_page(page);
} else {
print_bad_pte(vma, vmf->address, vmf->orig_pte, NULL);
ret = VM_FAULT_SIGBUS;
@@ -3282,7 +3324,6 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
goto out;
}

-
delayacct_set_flag(DELAYACCT_PF_SWAPIN);
page = lookup_swap_cache(entry, vma, vmf->address);
swapcache = page;
diff --git a/mm/page_vma_mapped.c b/mm/page_vma_mapped.c
index 86e3a3688d59..8fffae175104 100644
--- a/mm/page_vma_mapped.c
+++ b/mm/page_vma_mapped.c
@@ -93,10 +93,12 @@ static bool check_pte(struct page_vma_mapped_walk *pvmw)
return false;
entry = pte_to_swp_entry(*pvmw->pte);

- if (!is_migration_entry(entry))
+ if (is_migration_entry(entry))
+ pfn = migration_entry_to_pfn(entry);
+ else if (is_hwpoison_entry(entry))
+ pfn = hwpoison_entry_to_pfn(entry);
+ else
return false;
-
- pfn = migration_entry_to_pfn(entry);
} else if (is_swap_pte(*pvmw->pte)) {
swp_entry_t entry;

diff --git a/mm/rmap.c b/mm/rmap.c
index 08c56aaf72eb..f08d1fc28522 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -1575,7 +1575,7 @@ static bool try_to_unmap_one(struct page *page, struct vm_area_struct *vma,
dec_mm_counter(mm, mm_counter(page));
set_pte_at(mm, address, pvmw.pte, pteval);
}
-
+ get_page(page);
} else if (pte_unused(pteval) && !userfaultfd_armed(vma)) {
/*
* The guest indicated that the page content is of no
diff --git a/mm/shmem.c b/mm/shmem.c
index 7c6b6d8f6c39..d29a0c9be19c 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -1832,6 +1832,13 @@ static int shmem_getpage_gfp(struct inode *inode, pgoff_t index,

if (page)
hindex = page->index;
+
+ if (page && PageHWPoison(page)) {
+ unlock_page(page);
+ put_page(page);
+ return -EIO;
+ }
+
if (page && sgp == SGP_WRITE)
mark_page_accessed(page);

diff --git a/virt/kvm/Kconfig b/virt/kvm/Kconfig
index 1c37ccd5d402..50d7422386aa 100644
--- a/virt/kvm/Kconfig
+++ b/virt/kvm/Kconfig
@@ -63,3 +63,6 @@ config HAVE_KVM_NO_POLL

config KVM_XFER_TO_GUEST_WORK
bool
+
+config HAVE_KVM_PROTECTED_MEMORY
+ bool
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 8367d88ce39b..f182c54bfa34 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -51,6 +51,7 @@
#include <linux/io.h>
#include <linux/lockdep.h>
#include <linux/kthread.h>
+#include <linux/rmap.h>

#include <asm/processor.h>
#include <asm/ioctl.h>
@@ -2333,19 +2334,85 @@ static int next_segment(unsigned long len, int offset)
return len;
}

-static int __kvm_read_guest_page(struct kvm_memory_slot *slot, gfn_t gfn,
- void *data, int offset, int len)
+int copy_from_guest(struct kvm *kvm, void *data, unsigned long hva, int len)
+{
+ int offset = offset_in_page(hva);
+ struct page *page;
+ int npages, seg;
+ void *vaddr;
+
+ if (!IS_ENABLED(CONFIG_HAVE_KVM_PROTECTED_MEMORY) ||
+ !kvm->mem_protected) {
+ return __copy_from_user(data, (void __user *)hva, len);
+ }
+
+ might_fault();
+ kasan_check_write(data, len);
+ check_object_size(data, len, false);
+
+ while ((seg = next_segment(len, offset)) != 0) {
+ npages = get_user_pages_unlocked(hva, 1, &page, 0);
+ if (npages != 1)
+ return -EFAULT;
+
+ vaddr = kmap_atomic(page);
+ memcpy(data, vaddr + offset, seg);
+ kunmap_atomic(vaddr);
+
+ put_page(page);
+ len -= seg;
+ hva += seg;
+ data += seg;
+ offset = 0;
+ }
+
+ return 0;
+}
+
+int copy_to_guest(struct kvm *kvm, unsigned long hva, const void *data, int len)
+{
+ int offset = offset_in_page(hva);
+ struct page *page;
+ int npages, seg;
+ void *vaddr;
+
+ if (!IS_ENABLED(CONFIG_HAVE_KVM_PROTECTED_MEMORY) ||
+ !kvm->mem_protected) {
+ return __copy_to_user((void __user *)hva, data, len);
+ }
+
+ might_fault();
+ kasan_check_read(data, len);
+ check_object_size(data, len, true);
+
+ while ((seg = next_segment(len, offset)) != 0) {
+ npages = get_user_pages_unlocked(hva, 1, &page, FOLL_WRITE);
+ if (npages != 1)
+ return -EFAULT;
+
+ vaddr = kmap_atomic(page);
+ memcpy(vaddr + offset, data, seg);
+ kunmap_atomic(vaddr);
+
+ put_page(page);
+ len -= seg;
+ hva += seg;
+ data += seg;
+ offset = 0;
+ }
+
+ return 0;
+}
+
+static int __kvm_read_guest_page(struct kvm *kvm, struct kvm_memory_slot *slot,
+ gfn_t gfn, void *data, int offset, int len)
{
- int r;
unsigned long addr;

addr = gfn_to_hva_memslot_prot(slot, gfn, NULL);
if (kvm_is_error_hva(addr))
return -EFAULT;
- r = __copy_from_user(data, (void __user *)addr + offset, len);
- if (r)
- return -EFAULT;
- return 0;
+ return copy_from_guest(kvm, data, addr + offset, len);
}

int kvm_read_guest_page(struct kvm *kvm, gfn_t gfn, void *data, int offset,
@@ -2353,7 +2420,7 @@ int kvm_read_guest_page(struct kvm *kvm, gfn_t gfn, void *data, int offset,
{
struct kvm_memory_slot *slot = gfn_to_memslot(kvm, gfn);

- return __kvm_read_guest_page(slot, gfn, data, offset, len);
+ return __kvm_read_guest_page(kvm, slot, gfn, data, offset, len);
}
EXPORT_SYMBOL_GPL(kvm_read_guest_page);

@@ -2362,7 +2429,7 @@ int kvm_vcpu_read_guest_page(struct kvm_vcpu *vcpu, gfn_t gfn, void *data,
{
struct kvm_memory_slot *slot = kvm_vcpu_gfn_to_memslot(vcpu, gfn);

- return __kvm_read_guest_page(slot, gfn, data, offset, len);
+ return __kvm_read_guest_page(vcpu->kvm, slot, gfn, data, offset, len);
}
EXPORT_SYMBOL_GPL(kvm_vcpu_read_guest_page);

@@ -2444,7 +2511,8 @@ static int __kvm_write_guest_page(struct kvm *kvm,
addr = gfn_to_hva_memslot(memslot, gfn);
if (kvm_is_error_hva(addr))
return -EFAULT;
- r = __copy_to_user((void __user *)addr + offset, data, len);
+
+ r = copy_to_guest(kvm, addr + offset, data, len);
if (r)
return -EFAULT;
mark_page_dirty_in_slot(kvm, memslot, gfn);
@@ -2581,7 +2649,7 @@ int kvm_write_guest_offset_cached(struct kvm *kvm, struct gfn_to_hva_cache *ghc,
if (unlikely(!ghc->memslot))
return kvm_write_guest(kvm, gpa, data, len);

- r = __copy_to_user((void __user *)ghc->hva + offset, data, len);
+ r = copy_to_guest(kvm, ghc->hva + offset, data, len);
if (r)
return -EFAULT;
mark_page_dirty_in_slot(kvm, ghc->memslot, gpa >> PAGE_SHIFT);
@@ -2602,7 +2670,6 @@ int kvm_read_guest_offset_cached(struct kvm *kvm, struct gfn_to_hva_cache *ghc,
unsigned long len)
{
struct kvm_memslots *slots = kvm_memslots(kvm);
- int r;
gpa_t gpa = ghc->gpa + offset;

BUG_ON(len + offset > ghc->len);
@@ -2618,11 +2685,7 @@ int kvm_read_guest_offset_cached(struct kvm *kvm, struct gfn_to_hva_cache *ghc,
if (unlikely(!ghc->memslot))
return kvm_read_guest(kvm, gpa, data, len);

- r = __copy_from_user(data, (void __user *)ghc->hva + offset, len);
- if (r)
- return -EFAULT;
-
- return 0;
+ return copy_from_guest(kvm, data, ghc->hva + offset, len);
}
EXPORT_SYMBOL_GPL(kvm_read_guest_offset_cached);

@@ -2688,6 +2751,73 @@ void kvm_vcpu_mark_page_dirty(struct kvm_vcpu *vcpu, gfn_t gfn)
}
EXPORT_SYMBOL_GPL(kvm_vcpu_mark_page_dirty);

+int kvm_protect_memory(struct kvm *kvm)
+{
+ if (mmap_write_lock_killable(kvm->mm))
+ return -KVM_EINTR;
+ kvm->mem_protected = true;
+ kvm_arch_flush_shadow_all(kvm);
+ mmap_write_unlock(kvm->mm);
+
+ return 0;
+}
+
+bool gfn_is_shared(struct kvm *kvm, unsigned long gfn)
+{
+ bool ret = false;
+ int i;
+
+ spin_lock(&kvm->mmu_lock);
+ for (i = 0; i < kvm->nr_shared_ranges; i++) {
+ if (gfn < kvm->shared_ranges[i].start)
+ continue;
+ if (gfn >= kvm->shared_ranges[i].end)
+ continue;
+
+ ret = true;
+ break;
+ }
+ spin_unlock(&kvm->mmu_lock);
+
+ return ret;
+}
+
+int kvm_share_memory(struct kvm *kvm, unsigned long gfn, unsigned long npages)
+{
+ unsigned long end = gfn + npages;
+
+ if (!npages)
+ return 0;
+
+ /*
+ * Out of slots.
+ * Still worth to proceed: the new range may merge with an existing
+ * one.
+ */
+ WARN_ON_ONCE(kvm->nr_shared_ranges == ARRAY_SIZE(kvm->shared_ranges));
+
+ spin_lock(&kvm->mmu_lock);
+ kvm->nr_shared_ranges = add_range_with_merge(kvm->shared_ranges,
+ ARRAY_SIZE(kvm->shared_ranges),
+ kvm->nr_shared_ranges, gfn, end);
+ kvm->nr_shared_ranges = clean_sort_range(kvm->shared_ranges,
+ ARRAY_SIZE(kvm->shared_ranges));
+ spin_unlock(&kvm->mmu_lock);
+
+ for (; gfn < end; gfn++) {
+ struct page *page = gfn_to_page(kvm, gfn);
+
+ if (page == KVM_ERR_PTR_BAD_PAGE)
+ continue;
+ lock_page(page);
+ ClearPageHWPoison(page);
+ unlock_page(page);
+ put_page(page);
+ }
+
+ return 0;
+}
+
void kvm_sigset_activate(struct kvm_vcpu *vcpu)
{
if (!vcpu->sigset_active)
--
2.26.3