[RFC 14/16] KVM: Introduce gfn_to_pfn_memslot_protected()

Kirill A. Shutemov
2020-05-22T12:52:42Z

The new interface allows to detect if the page is protected.
A protected page cannot be accessed directly by the host: it has to be
mapped manually.

This is preparation for the next patch.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
---
arch/powerpc/kvm/book3s_64_mmu_hv.c | 2 +-
arch/powerpc/kvm/book3s_64_mmu_radix.c | 2 +-
arch/x86/kvm/mmu/mmu.c | 6 +++--
include/linux/kvm_host.h | 2 +-
virt/kvm/kvm_main.c | 35 ++++++++++++++++++--------
5 files changed, 32 insertions(+), 15 deletions(-)

diff --git a/arch/powerpc/kvm/book3s_64_mmu_hv.c b/arch/powerpc/kvm/book3s_64_mmu_hv.c
index 2b35f9bcf892..e9a13ecf812f 100644
--- a/arch/powerpc/kvm/book3s_64_mmu_hv.c
+++ b/arch/powerpc/kvm/book3s_64_mmu_hv.c
@@ -587,7 +587,7 @@ int kvmppc_book3s_hv_page_fault(struct kvm_run *run, 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 aa12cd4078b3..58f8df466a94 100644
--- a/arch/powerpc/kvm/book3s_64_mmu_radix.c
+++ b/arch/powerpc/kvm/book3s_64_mmu_radix.c
@@ -798,7 +798,7 @@ 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/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 8071952e9cf2..0fc095a66a3c 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -4096,7 +4096,8 @@ static bool try_async_pf(struct kvm_vcpu *vcpu, bool prefault, gfn_t gfn,

slot = kvm_vcpu_gfn_to_memslot(vcpu, 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 */

@@ -4110,7 +4111,8 @@ 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/include/linux/kvm_host.h b/include/linux/kvm_host.h
index d7072f6d6aa0..eca18ef9b1f4 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -724,7 +724,7 @@ 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/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 63282def3760..8bcf3201304a 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -1779,9 +1779,10 @@ 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;

@@ -1795,9 +1796,15 @@ 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)
+ down_read(&current->mm->mmap_sem);
+ npages = get_user_pages(addr, 1, flags, &page, &vma);
+ if (npages != 1) {
+ up_read(&current->mm->mmap_sem);
return npages;
+ }
+ if (protected)
+ *protected = vma_is_kvm_protected(vma);
+ up_read(&current->mm->mmap_sem);

/* map read fault as writable if possible */
if (unlikely(!write_fault) && writable) {
@@ -1888,7 +1895,7 @@ 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;
@@ -1903,7 +1910,8 @@ 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;

@@ -1937,7 +1945,7 @@ 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);

@@ -1960,7 +1968,7 @@ 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);

@@ -1968,19 +1976,26 @@ 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);

--
2.26.2