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From: Alexandru Elisei <alexandru.elisei@arm.com>
To: linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu
Cc: maz@kernel.org
Subject: [PATCH 1/2] KVM: arm64: Update page shift if stage 2 block mapping not supported
Date: Tue,  1 Sep 2020 14:33:56 +0100	[thread overview]
Message-ID: <20200901133357.52640-2-alexandru.elisei@arm.com> (raw)
In-Reply-To: <20200901133357.52640-1-alexandru.elisei@arm.com>

Commit 196f878a7ac2e (" KVM: arm/arm64: Signal SIGBUS when stage2 discovers
hwpoison memory") modifies user_mem_abort() to send a SIGBUS signal when
the fault IPA maps to a hwpoisoned page. Commit 1559b7583ff6 ("KVM:
arm/arm64: Re-check VMA on detecting a poisoned page") changed
kvm_send_hwpoison_signal() to use the page shift instead of the VMA because
at that point the code had already released the mmap lock, which means
userspace could have modified the VMA.

If userspace uses hugetlbfs for the VM memory, user_mem_abort() tries to
map the guest fault IPA using block mappings in stage 2. That is not always
possible, if, for example, userspace uses dirty page logging for the VM.
Update the page shift appropriately in those cases when we downgrade the
stage 2 entry from a block mapping to a page.

Fixes: 1559b7583ff6 ("KVM: arm/arm64: Re-check VMA on detecting a poisoned page")
Signed-off-by: Alexandru Elisei <alexandru.elisei@arm.com>
---
 arch/arm64/kvm/mmu.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
index ba00bcc0c884..25e7dc52c086 100644
--- a/arch/arm64/kvm/mmu.c
+++ b/arch/arm64/kvm/mmu.c
@@ -1877,6 +1877,7 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
 	    !fault_supports_stage2_huge_mapping(memslot, hva, vma_pagesize)) {
 		force_pte = true;
 		vma_pagesize = PAGE_SIZE;
+		vma_shift = PAGE_SHIFT;
 	}
 
 	/*
-- 
2.28.0

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kvmarm@lists.cs.columbia.edu
https://lists.cs.columbia.edu/mailman/listinfo/kvmarm

WARNING: multiple messages have this Message-ID (diff)
From: Alexandru Elisei <alexandru.elisei@arm.com>
To: linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu
Cc: maz@kernel.org, james.morse@arm.com,
	julien.thierry.kdev@gmail.com, suzuki.poulose@arm.com
Subject: [PATCH 1/2] KVM: arm64: Update page shift if stage 2 block mapping not supported
Date: Tue,  1 Sep 2020 14:33:56 +0100	[thread overview]
Message-ID: <20200901133357.52640-2-alexandru.elisei@arm.com> (raw)
In-Reply-To: <20200901133357.52640-1-alexandru.elisei@arm.com>

Commit 196f878a7ac2e (" KVM: arm/arm64: Signal SIGBUS when stage2 discovers
hwpoison memory") modifies user_mem_abort() to send a SIGBUS signal when
the fault IPA maps to a hwpoisoned page. Commit 1559b7583ff6 ("KVM:
arm/arm64: Re-check VMA on detecting a poisoned page") changed
kvm_send_hwpoison_signal() to use the page shift instead of the VMA because
at that point the code had already released the mmap lock, which means
userspace could have modified the VMA.

If userspace uses hugetlbfs for the VM memory, user_mem_abort() tries to
map the guest fault IPA using block mappings in stage 2. That is not always
possible, if, for example, userspace uses dirty page logging for the VM.
Update the page shift appropriately in those cases when we downgrade the
stage 2 entry from a block mapping to a page.

Fixes: 1559b7583ff6 ("KVM: arm/arm64: Re-check VMA on detecting a poisoned page")
Signed-off-by: Alexandru Elisei <alexandru.elisei@arm.com>
---
 arch/arm64/kvm/mmu.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
index ba00bcc0c884..25e7dc52c086 100644
--- a/arch/arm64/kvm/mmu.c
+++ b/arch/arm64/kvm/mmu.c
@@ -1877,6 +1877,7 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
 	    !fault_supports_stage2_huge_mapping(memslot, hva, vma_pagesize)) {
 		force_pte = true;
 		vma_pagesize = PAGE_SIZE;
+		vma_shift = PAGE_SHIFT;
 	}
 
 	/*
-- 
2.28.0


_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

  reply	other threads:[~2020-09-01 13:33 UTC|newest]

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-09-01 13:33 [PATCH 0/2] KVM: arm64: user_mem_abort() improvements Alexandru Elisei
2020-09-01 13:33 ` Alexandru Elisei
2020-09-01 13:33 ` Alexandru Elisei [this message]
2020-09-01 13:33   ` [PATCH 1/2] KVM: arm64: Update page shift if stage 2 block mapping not supported Alexandru Elisei
2020-09-02  0:57   ` Gavin Shan
2020-09-02  0:57     ` Gavin Shan
2020-09-01 13:33 ` [PATCH 2/2] KVM: arm64: Try PMD block mappings if PUD mappings are " Alexandru Elisei
2020-09-01 13:33   ` Alexandru Elisei
2020-09-02  1:23   ` Gavin Shan
2020-09-02  1:23     ` Gavin Shan
2020-09-02  9:01     ` Alexandru Elisei
2020-09-02  9:01       ` Alexandru Elisei
2020-09-03  0:06       ` Gavin Shan
2020-09-03  0:06         ` Gavin Shan
2020-09-04  9:58   ` Marc Zyngier
2020-09-04  9:58     ` Marc Zyngier
2020-09-08 12:23     ` Alexandru Elisei
2020-09-08 12:23       ` Alexandru Elisei
2020-09-08 12:41       ` Marc Zyngier
2020-09-08 12:41         ` Marc Zyngier
2020-09-04 10:18 ` [PATCH 0/2] KVM: arm64: user_mem_abort() improvements Marc Zyngier
2020-09-04 10:18   ` Marc Zyngier

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