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Subject[PATCH AUTOSEL 5.0 29/98] KVM: arm/arm64: Enforce PTE mappings at stage2 when needed
Date
From: Suzuki K Poulose <suzuki.poulose@arm.com>

[ Upstream commit a80868f398554842b14d07060012c06efb57c456 ]

commit 6794ad5443a2118 ("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 : 6794ad5443a2118 ("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>
Signed-off-by: Sasha Levin (Microsoft) <sashal@kernel.org>
---
virt/kvm/arm/mmu.c | 43 +++++++++++++++++++++----------------------
1 file changed, 21 insertions(+), 22 deletions(-)

diff --git a/virt/kvm/arm/mmu.c b/virt/kvm/arm/mmu.c
index 5cc22cdaa5ba..6dccb36465e6 100644
--- a/virt/kvm/arm/mmu.c
+++ b/virt/kvm/arm/mmu.c
@@ -1595,8 +1595,9 @@ 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, gpa_end;
hva_t uaddr_start, uaddr_end;
@@ -1612,34 +1613,34 @@ 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).
@@ -1648,8 +1649,8 @@ 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,
@@ -1678,12 +1679,6 @@ 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);
@@ -1694,6 +1689,12 @@ 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
@@ -1701,11 +1702,9 @@ 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 */
--
2.19.1
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