[RFCv2 14/16] KVM: Handle protected memory in __kvm_map_gfn()/__kvm_unmap_gfn()

From: Kirill A. Shutemov
Date: Tue Oct 20 2020 - 02:20:09 EST

We cannot access protected pages directly. Use ioremap() to
create a temporary mapping of the page. The mapping is destroyed
on __kvm_unmap_gfn().

The new interface gfn_to_pfn_memslot_protected() is used to detect if
the page is protected.

ioremap_cache_force() is a hack to bypass IORES_MAP_SYSTEM_RAM check in
the x86 ioremap code. We need a better solution.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
---
arch/powerpc/kvm/book3s_64_mmu_hv.c | 2 +-
arch/powerpc/kvm/book3s_64_mmu_radix.c | 2 +-
arch/x86/include/asm/io.h | 2 +
arch/x86/include/asm/pgtable_types.h | 1 +
arch/x86/kvm/mmu/mmu.c | 6 ++-
arch/x86/mm/ioremap.c | 16 ++++++--
include/linux/kvm_host.h | 3 +-
include/linux/kvm_types.h | 1 +
virt/kvm/kvm_main.c | 52 +++++++++++++++++++-------
9 files changed, 63 insertions(+), 22 deletions(-)

diff --git a/arch/powerpc/kvm/book3s_64_mmu_hv.c b/arch/powerpc/kvm/book3s_64_mmu_hv.c
index 38ea396a23d6..8e06cd3f759c 100644
--- a/arch/powerpc/kvm/book3s_64_mmu_hv.c
+++ b/arch/powerpc/kvm/book3s_64_mmu_hv.c
@@ -590,7 +590,7 @@ int kvmppc_book3s_hv_page_fault(struct kvm_vcpu *vcpu,
} else {
/* Call KVM generic code to do the slow-path check */
pfn = __gfn_to_pfn_memslot(memslot, gfn, false, NULL,
- writing, &write_ok);
+ writing, &write_ok, NULL);
if (is_error_noslot_pfn(pfn))
return -EFAULT;
page = NULL;
diff --git a/arch/powerpc/kvm/book3s_64_mmu_radix.c b/arch/powerpc/kvm/book3s_64_mmu_radix.c
index 22a677b18695..6fd4e3f9b66a 100644
--- a/arch/powerpc/kvm/book3s_64_mmu_radix.c
+++ b/arch/powerpc/kvm/book3s_64_mmu_radix.c
@@ -822,7 +822,7 @@ int kvmppc_book3s_instantiate_page(struct kvm_vcpu *vcpu,

/* Call KVM generic code to do the slow-path check */
pfn = __gfn_to_pfn_memslot(memslot, gfn, false, NULL,
- writing, upgrade_p);
+ writing, upgrade_p, NULL);
if (is_error_noslot_pfn(pfn))
return -EFAULT;
page = NULL;
diff --git a/arch/x86/include/asm/io.h b/arch/x86/include/asm/io.h
index c58d52fd7bf2..a3e1bfad1026 100644
--- a/arch/x86/include/asm/io.h
+++ b/arch/x86/include/asm/io.h
@@ -184,6 +184,8 @@ extern void __iomem *ioremap_uc(resource_size_t offset, unsigned long size);
#define ioremap_uc ioremap_uc
extern void __iomem *ioremap_cache(resource_size_t offset, unsigned long size);
#define ioremap_cache ioremap_cache
+extern void __iomem *ioremap_cache_force(resource_size_t offset, unsigned long size);
+#define ioremap_cache_force ioremap_cache_force
extern void __iomem *ioremap_prot(resource_size_t offset, unsigned long size, unsigned long prot_val);
#define ioremap_prot ioremap_prot
extern void __iomem *ioremap_encrypted(resource_size_t phys_addr, unsigned long size);
diff --git a/arch/x86/include/asm/pgtable_types.h b/arch/x86/include/asm/pgtable_types.h
index 816b31c68550..4c16a9583786 100644
--- a/arch/x86/include/asm/pgtable_types.h
+++ b/arch/x86/include/asm/pgtable_types.h
@@ -147,6 +147,7 @@ enum page_cache_mode {
_PAGE_CACHE_MODE_UC = 3,
_PAGE_CACHE_MODE_WT = 4,
_PAGE_CACHE_MODE_WP = 5,
+ _PAGE_CACHE_MODE_WB_FORCE = 6,

_PAGE_CACHE_MODE_NUM = 8
};
diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 71aa3da2a0b7..162cb285b87b 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -4058,7 +4058,8 @@ static bool try_async_pf(struct kvm_vcpu *vcpu, bool prefault, gfn_t gfn,
}

async = false;
- *pfn = __gfn_to_pfn_memslot(slot, gfn, false, &async, write, writable);
+ *pfn = __gfn_to_pfn_memslot(slot, gfn, false, &async, write, writable,
+ NULL);
if (!async)
return false; /* *pfn has correct page already */

@@ -4072,7 +4073,8 @@ static bool try_async_pf(struct kvm_vcpu *vcpu, bool prefault, gfn_t gfn,
return true;
}

- *pfn = __gfn_to_pfn_memslot(slot, gfn, false, NULL, write, writable);
+ *pfn = __gfn_to_pfn_memslot(slot, gfn, false, NULL, write, writable,
+ NULL);
return false;
}

diff --git a/arch/x86/mm/ioremap.c b/arch/x86/mm/ioremap.c
index 9e5ccc56f8e0..4409785e294c 100644
--- a/arch/x86/mm/ioremap.c
+++ b/arch/x86/mm/ioremap.c
@@ -202,9 +202,12 @@ __ioremap_caller(resource_size_t phys_addr, unsigned long size,
__ioremap_check_mem(phys_addr, size, &io_desc);

/*
- * Don't allow anybody to remap normal RAM that we're using..
+ * Don't allow anybody to remap normal RAM that we're using, unless
+ * _PAGE_CACHE_MODE_WB_FORCE is used.
*/
- if (io_desc.flags & IORES_MAP_SYSTEM_RAM) {
+ if (pcm == _PAGE_CACHE_MODE_WB_FORCE) {
+ pcm = _PAGE_CACHE_MODE_WB;
+ } else if (io_desc.flags & IORES_MAP_SYSTEM_RAM) {
WARN_ONCE(1, "ioremap on RAM at %pa - %pa\n",
&phys_addr, &last_addr);
return NULL;
@@ -419,6 +422,13 @@ void __iomem *ioremap_cache(resource_size_t phys_addr, unsigned long size)
}
EXPORT_SYMBOL(ioremap_cache);

+void __iomem *ioremap_cache_force(resource_size_t phys_addr, unsigned long size)
+{
+ return __ioremap_caller(phys_addr, size, _PAGE_CACHE_MODE_WB_FORCE,
+ __builtin_return_address(0), false);
+}
+EXPORT_SYMBOL(ioremap_cache_force);
+
void __iomem *ioremap_prot(resource_size_t phys_addr, unsigned long size,
unsigned long prot_val)
{
@@ -467,7 +477,7 @@ void iounmap(volatile void __iomem *addr)
p = find_vm_area((void __force *)addr);

if (!p) {
- printk(KERN_ERR "iounmap: bad address %p\n", addr);
+ printk(KERN_ERR "iounmap: bad address %px\n", addr);
dump_stack();
return;
}
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 6655e8da4555..0d5f3885747b 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -238,6 +238,7 @@ struct kvm_host_map {
void *hva;
kvm_pfn_t pfn;
kvm_pfn_t gfn;
+ bool protected;
};

/*
@@ -725,7 +726,7 @@ kvm_pfn_t gfn_to_pfn_memslot(struct kvm_memory_slot *slot, gfn_t gfn);
kvm_pfn_t gfn_to_pfn_memslot_atomic(struct kvm_memory_slot *slot, gfn_t gfn);
kvm_pfn_t __gfn_to_pfn_memslot(struct kvm_memory_slot *slot, gfn_t gfn,
bool atomic, bool *async, bool write_fault,
- bool *writable);
+ bool *writable, bool *protected);

void kvm_release_pfn_clean(kvm_pfn_t pfn);
void kvm_release_pfn_dirty(kvm_pfn_t pfn);
diff --git a/include/linux/kvm_types.h b/include/linux/kvm_types.h
index a7580f69dda0..0a8c6426b4f4 100644
--- a/include/linux/kvm_types.h
+++ b/include/linux/kvm_types.h
@@ -58,6 +58,7 @@ struct gfn_to_pfn_cache {
gfn_t gfn;
kvm_pfn_t pfn;
bool dirty;
+ bool protected;
};

#ifdef KVM_ARCH_NR_OBJS_PER_MEMORY_CACHE
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 9b569b78874a..7c2c764c28c5 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -1852,9 +1852,10 @@ static bool hva_to_pfn_fast(unsigned long addr, bool write_fault,
* 1 indicates success, -errno is returned if error is detected.
*/
static int hva_to_pfn_slow(unsigned long addr, bool *async, bool write_fault,
- bool *writable, kvm_pfn_t *pfn)
+ bool *writable, bool *protected, kvm_pfn_t *pfn)
{
unsigned int flags = FOLL_HWPOISON | FOLL_KVM;
+ struct vm_area_struct *vma;
struct page *page;
int npages = 0;

@@ -1868,9 +1869,15 @@ static int hva_to_pfn_slow(unsigned long addr, bool *async, bool write_fault,
if (async)
flags |= FOLL_NOWAIT;

- npages = get_user_pages_unlocked(addr, 1, &page, flags);
- if (npages != 1)
+ mmap_read_lock(current->mm);
+ npages = get_user_pages(addr, 1, flags, &page, &vma);
+ if (npages != 1) {
+ mmap_read_unlock(current->mm);
return npages;
+ }
+ if (protected)
+ *protected = vma_is_kvm_protected(vma);
+ mmap_read_unlock(current->mm);

/* map read fault as writable if possible */
if (unlikely(!write_fault) && writable) {
@@ -1961,7 +1968,7 @@ static int hva_to_pfn_remapped(struct vm_area_struct *vma,
* whether the mapping is writable.
*/
static kvm_pfn_t hva_to_pfn(unsigned long addr, bool atomic, bool *async,
- bool write_fault, bool *writable)
+ bool write_fault, bool *writable, bool *protected)
{
struct vm_area_struct *vma;
kvm_pfn_t pfn = 0;
@@ -1976,7 +1983,8 @@ static kvm_pfn_t hva_to_pfn(unsigned long addr, bool atomic, bool *async,
if (atomic)
return KVM_PFN_ERR_FAULT;

- npages = hva_to_pfn_slow(addr, async, write_fault, writable, &pfn);
+ npages = hva_to_pfn_slow(addr, async, write_fault, writable, protected,
+ &pfn);
if (npages == 1)
return pfn;

@@ -2010,7 +2018,7 @@ static kvm_pfn_t hva_to_pfn(unsigned long addr, bool atomic, bool *async,

kvm_pfn_t __gfn_to_pfn_memslot(struct kvm_memory_slot *slot, gfn_t gfn,
bool atomic, bool *async, bool write_fault,
- bool *writable)
+ bool *writable, bool *protected)
{
unsigned long addr = __gfn_to_hva_many(slot, gfn, NULL, write_fault);

@@ -2033,7 +2041,7 @@ kvm_pfn_t __gfn_to_pfn_memslot(struct kvm_memory_slot *slot, gfn_t gfn,
}

return hva_to_pfn(addr, atomic, async, write_fault,
- writable);
+ writable, protected);
}
EXPORT_SYMBOL_GPL(__gfn_to_pfn_memslot);

@@ -2041,19 +2049,26 @@ kvm_pfn_t gfn_to_pfn_prot(struct kvm *kvm, gfn_t gfn, bool write_fault,
bool *writable)
{
return __gfn_to_pfn_memslot(gfn_to_memslot(kvm, gfn), gfn, false, NULL,
- write_fault, writable);
+ write_fault, writable, NULL);
}
EXPORT_SYMBOL_GPL(gfn_to_pfn_prot);

kvm_pfn_t gfn_to_pfn_memslot(struct kvm_memory_slot *slot, gfn_t gfn)
{
- return __gfn_to_pfn_memslot(slot, gfn, false, NULL, true, NULL);
+ return __gfn_to_pfn_memslot(slot, gfn, false, NULL, true, NULL, NULL);
}
EXPORT_SYMBOL_GPL(gfn_to_pfn_memslot);

+static kvm_pfn_t gfn_to_pfn_memslot_protected(struct kvm_memory_slot *slot,
+ gfn_t gfn, bool *protected)
+{
+ return __gfn_to_pfn_memslot(slot, gfn, false, NULL, true, NULL,
+ protected);
+}
+
kvm_pfn_t gfn_to_pfn_memslot_atomic(struct kvm_memory_slot *slot, gfn_t gfn)
{
- return __gfn_to_pfn_memslot(slot, gfn, true, NULL, true, NULL);
+ return __gfn_to_pfn_memslot(slot, gfn, true, NULL, true, NULL, NULL);
}
EXPORT_SYMBOL_GPL(gfn_to_pfn_memslot_atomic);

@@ -2134,7 +2149,7 @@ static void kvm_cache_gfn_to_pfn(struct kvm_memory_slot *slot, gfn_t gfn,
{
kvm_release_pfn(cache->pfn, cache->dirty, cache);

- cache->pfn = gfn_to_pfn_memslot(slot, gfn);
+ cache->pfn = gfn_to_pfn_memslot_protected(slot, gfn, &cache->protected);
cache->gfn = gfn;
cache->dirty = false;
cache->generation = gen;
@@ -2149,6 +2164,7 @@ static int __kvm_map_gfn(struct kvm_memslots *slots, gfn_t gfn,
void *hva = NULL;
struct page *page = KVM_UNMAPPED_PAGE;
struct kvm_memory_slot *slot = __gfn_to_memslot(slots, gfn);
+ bool protected;
u64 gen = slots->generation;

if (!map)
@@ -2162,15 +2178,20 @@ static int __kvm_map_gfn(struct kvm_memslots *slots, gfn_t gfn,
kvm_cache_gfn_to_pfn(slot, gfn, cache, gen);
}
pfn = cache->pfn;
+ protected = cache->protected;
} else {
if (atomic)
return -EAGAIN;
- pfn = gfn_to_pfn_memslot(slot, gfn);
+ pfn = gfn_to_pfn_memslot_protected(slot, gfn, &protected);
}
if (is_error_noslot_pfn(pfn))
return -EINVAL;

- if (pfn_valid(pfn)) {
+ if (protected) {
+ if (atomic)
+ return -EAGAIN;
+ hva = ioremap_cache_force(pfn_to_hpa(pfn), PAGE_SIZE);
+ } else if (pfn_valid(pfn)) {
page = pfn_to_page(pfn);
if (atomic)
hva = kmap_atomic(page);
@@ -2191,6 +2212,7 @@ static int __kvm_map_gfn(struct kvm_memslots *slots, gfn_t gfn,
map->hva = hva;
map->pfn = pfn;
map->gfn = gfn;
+ map->protected = protected;

return 0;
}
@@ -2221,7 +2243,9 @@ static void __kvm_unmap_gfn(struct kvm_memory_slot *memslot,
if (!map->hva)
return;

- if (map->page != KVM_UNMAPPED_PAGE) {
+ if (map->protected) {
+ iounmap(map->hva);
+ } else if (map->page != KVM_UNMAPPED_PAGE) {
if (atomic)
kunmap_atomic(map->hva);
else
--
2.26.2