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KVM: arm/arm64: Enforce PTE mappings at stage2 when needed 

commit 6794ad5443 ("KVM: arm/arm64: Fix unintended stage 2 PMD mappings")
made the checks to skip huge mappings, stricter. However it introduced
a bug where we still use huge mappings, ignoring the flag to
use PTE mappings, by not reseting the vma_pagesize to PAGE_SIZE.

Also, the checks do not cover the PUD huge pages, that was
under review during the same period. This patch fixes both
the issues.

Fixes : 6794ad5443 ("KVM: arm/arm64: Fix unintended stage 2 PMD mappings")
Reported-by: Zenghui Yu <yuzenghui@huawei.com>
Cc: Zenghui Yu <yuzenghui@huawei.com>
Cc: Christoffer Dall <christoffer.dall@arm.com>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
This commit is contained in:
Suzuki K Poulose 2019-03-12 09:52:51 +00:00 committed by Marc Zyngier
parent 7494cec6cb
commit a80868f398
1 changed files with 21 additions and 22 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

43
virt/kvm/arm/mmu.c
View File

@ -1594,8 +1594,9 @@ static void kvm_send_hwpoison_signal(unsigned long address,
send_sig_mceerr(BUS_MCEERR_AR, (void __user *)address, lsb, current);
}
static bool fault_supports_stage2_pmd_mappings(struct kvm_memory_slot *memslot,
unsigned long hva)
static bool fault_supports_stage2_huge_mapping(struct kvm_memory_slot *memslot,
unsigned long hva,
unsigned long map_size)
{
gpa_t gpa_start;
hva_t uaddr_start, uaddr_end;
@ -1610,34 +1611,34 @@ static bool fault_supports_stage2_pmd_mappings(struct kvm_memory_slot *memslot,
/*
* Pages belonging to memslots that don't have the same alignment
* within a PMD for userspace and IPA cannot be mapped with stage-2
* PMD entries, because we'll end up mapping the wrong pages.
* within a PMD/PUD for userspace and IPA cannot be mapped with stage-2
* PMD/PUD entries, because we'll end up mapping the wrong pages.
*
* Consider a layout like the following:
*
* memslot->userspace_addr:
* +-----+--------------------+--------------------+---+
* |abcde|fgh Stage-1 PMD | Stage-1 PMD tv|xyz|
* |abcde|fgh Stage-1 block | Stage-1 block tv|xyz|
* +-----+--------------------+--------------------+---+
*
* memslot->base_gfn << PAGE_SIZE:
* +---+--------------------+--------------------+-----+
* |abc|def Stage-2 PMD | Stage-2 PMD |tvxyz|
* |abc|def Stage-2 block | Stage-2 block |tvxyz|
* +---+--------------------+--------------------+-----+
*
* If we create those stage-2 PMDs, we'll end up with this incorrect
* If we create those stage-2 blocks, we'll end up with this incorrect
* mapping:
* d -> f
* e -> g
* f -> h
*/
if ((gpa_start & ~S2_PMD_MASK) != (uaddr_start & ~S2_PMD_MASK))
if ((gpa_start & (map_size - 1)) != (uaddr_start & (map_size - 1)))
return false;
/*
* Next, let's make sure we're not trying to map anything not covered
* by the memslot. This means we have to prohibit PMD size mappings
* for the beginning and end of a non-PMD aligned and non-PMD sized
* by the memslot. This means we have to prohibit block size mappings
* for the beginning and end of a non-block aligned and non-block sized
* memory slot (illustrated by the head and tail parts of the
* userspace view above containing pages 'abcde' and 'xyz',
* respectively).
@ -1646,8 +1647,8 @@ static bool fault_supports_stage2_pmd_mappings(struct kvm_memory_slot *memslot,
* userspace_addr or the base_gfn, as both are equally aligned (per
* the check above) and equally sized.
*/
return (hva & S2_PMD_MASK) >= uaddr_start &&
(hva & S2_PMD_MASK) + S2_PMD_SIZE <= uaddr_end;
return (hva & ~(map_size - 1)) >= uaddr_start &&
(hva & ~(map_size - 1)) + map_size <= uaddr_end;
}
static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
@ -1676,12 +1677,6 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
return -EFAULT;
}
if (!fault_supports_stage2_pmd_mappings(memslot, hva))
force_pte = true;
if (logging_active)
force_pte = true;
/* Let's check if we will get back a huge page backed by hugetlbfs */
down_read(&current->mm->mmap_sem);
vma = find_vma_intersection(current->mm, hva, hva + 1);
@ -1692,6 +1687,12 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
}
vma_pagesize = vma_kernel_pagesize(vma);
if (logging_active ||
!fault_supports_stage2_huge_mapping(memslot, hva, vma_pagesize)) {
force_pte = true;
vma_pagesize = PAGE_SIZE;
}
/*
* The stage2 has a minimum of 2 level table (For arm64 see
* kvm_arm_setup_stage2()). Hence, we are guaranteed that we can
@ -1699,11 +1700,9 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
* As for PUD huge maps, we must make sure that we have at least
* 3 levels, i.e, PMD is not folded.
*/
if ((vma_pagesize == PMD_SIZE ||
(vma_pagesize == PUD_SIZE && kvm_stage2_has_pmd(kvm))) &&
!force_pte) {
if (vma_pagesize == PMD_SIZE ||
(vma_pagesize == PUD_SIZE && kvm_stage2_has_pmd(kvm)))
gfn = (fault_ipa & huge_page_mask(hstate_vma(vma))) >> PAGE_SHIFT;
}
up_read(&current->mm->mmap_sem);
/* We need minimum second+third level pages */