From: Quentin Perret <qperret@google.com>
To: maz@kernel.org, james.morse@arm.com, alexandru.elisei@arm.com,
suzuki.poulose@arm.com, catalin.marinas@arm.com, will@kernel.org
Cc: linux-arm-kernel@lists.infradead.org,
kvmarm@lists.cs.columbia.edu, linux-kernel@vger.kernel.org,
ardb@kernel.org, qwandor@google.com, tabba@google.com,
dbrazdil@google.com, kernel-team@android.com,
Quentin Perret <qperret@google.com>
Subject: [PATCH v3 20/21] KVM: arm64: Restrict EL2 stage-1 changes in protected mode
Date: Thu, 29 Jul 2021 14:28:17 +0100 [thread overview]
Message-ID: <20210729132818.4091769-21-qperret@google.com> (raw)
In-Reply-To: <20210729132818.4091769-1-qperret@google.com>
The host kernel is currently able to change EL2 stage-1 mappings without
restrictions thanks to the __pkvm_create_mappings() hypercall. But in a
world where the host is no longer part of the TCB, this clearly poses a
problem.
To fix this, introduce a new hypercall to allow the host to share a
physical memory page with the hypervisor, and remove the
__pkvm_create_mappings() variant. The new hypercall implements
ownership and permission checks before allowing the sharing operation,
and it annotates the shared page in the hypervisor stage-1 and host
stage-2 page-tables.
Signed-off-by: Quentin Perret <qperret@google.com>
---
arch/arm64/include/asm/kvm_asm.h | 2 +-
arch/arm64/kvm/hyp/include/nvhe/mem_protect.h | 1 +
arch/arm64/kvm/hyp/nvhe/hyp-main.c | 11 +--
arch/arm64/kvm/hyp/nvhe/mem_protect.c | 89 +++++++++++++++++++
arch/arm64/kvm/mmu.c | 28 +++++-
5 files changed, 119 insertions(+), 12 deletions(-)
diff --git a/arch/arm64/include/asm/kvm_asm.h b/arch/arm64/include/asm/kvm_asm.h
index 432a9ea1f02e..aed2aa61766a 100644
--- a/arch/arm64/include/asm/kvm_asm.h
+++ b/arch/arm64/include/asm/kvm_asm.h
@@ -59,7 +59,7 @@
#define __KVM_HOST_SMCCC_FUNC___vgic_v3_save_aprs 13
#define __KVM_HOST_SMCCC_FUNC___vgic_v3_restore_aprs 14
#define __KVM_HOST_SMCCC_FUNC___pkvm_init 15
-#define __KVM_HOST_SMCCC_FUNC___pkvm_create_mappings 16
+#define __KVM_HOST_SMCCC_FUNC___pkvm_host_share_hyp 16
#define __KVM_HOST_SMCCC_FUNC___pkvm_create_private_mapping 17
#define __KVM_HOST_SMCCC_FUNC___pkvm_cpu_set_vector 18
#define __KVM_HOST_SMCCC_FUNC___pkvm_prot_finalize 19
diff --git a/arch/arm64/kvm/hyp/include/nvhe/mem_protect.h b/arch/arm64/kvm/hyp/include/nvhe/mem_protect.h
index 7ce36fbf5158..3d78d7782f1b 100644
--- a/arch/arm64/kvm/hyp/include/nvhe/mem_protect.h
+++ b/arch/arm64/kvm/hyp/include/nvhe/mem_protect.h
@@ -49,6 +49,7 @@ extern struct host_kvm host_kvm;
extern const u8 pkvm_hyp_id;
int __pkvm_prot_finalize(void);
+int __pkvm_host_share_hyp(u64 pfn);
bool addr_is_memory(phys_addr_t phys);
int host_stage2_idmap_locked(u64 start, u64 end, enum kvm_pgtable_prot prot);
diff --git a/arch/arm64/kvm/hyp/nvhe/hyp-main.c b/arch/arm64/kvm/hyp/nvhe/hyp-main.c
index 7900d5b66ba3..2da6aa8da868 100644
--- a/arch/arm64/kvm/hyp/nvhe/hyp-main.c
+++ b/arch/arm64/kvm/hyp/nvhe/hyp-main.c
@@ -140,14 +140,11 @@ static void handle___pkvm_cpu_set_vector(struct kvm_cpu_context *host_ctxt)
cpu_reg(host_ctxt, 1) = pkvm_cpu_set_vector(slot);
}
-static void handle___pkvm_create_mappings(struct kvm_cpu_context *host_ctxt)
+static void handle___pkvm_host_share_hyp(struct kvm_cpu_context *host_ctxt)
{
- DECLARE_REG(unsigned long, start, host_ctxt, 1);
- DECLARE_REG(unsigned long, size, host_ctxt, 2);
- DECLARE_REG(unsigned long, phys, host_ctxt, 3);
- DECLARE_REG(enum kvm_pgtable_prot, prot, host_ctxt, 4);
+ DECLARE_REG(u64, pfn, host_ctxt, 1);
- cpu_reg(host_ctxt, 1) = __pkvm_create_mappings(start, size, phys, prot);
+ cpu_reg(host_ctxt, 1) = __pkvm_host_share_hyp(pfn);
}
static void handle___pkvm_create_private_mapping(struct kvm_cpu_context *host_ctxt)
@@ -185,7 +182,7 @@ static const hcall_t host_hcall[] = {
HANDLE_FUNC(__vgic_v3_restore_aprs),
HANDLE_FUNC(__pkvm_init),
HANDLE_FUNC(__pkvm_cpu_set_vector),
- HANDLE_FUNC(__pkvm_create_mappings),
+ HANDLE_FUNC(__pkvm_host_share_hyp),
HANDLE_FUNC(__pkvm_create_private_mapping),
HANDLE_FUNC(__pkvm_prot_finalize),
};
diff --git a/arch/arm64/kvm/hyp/nvhe/mem_protect.c b/arch/arm64/kvm/hyp/nvhe/mem_protect.c
index 0ccea58df7e0..1b67f562b6fc 100644
--- a/arch/arm64/kvm/hyp/nvhe/mem_protect.c
+++ b/arch/arm64/kvm/hyp/nvhe/mem_protect.c
@@ -338,6 +338,95 @@ static int host_stage2_idmap(u64 addr)
return ret;
}
+static inline bool check_prot(enum kvm_pgtable_prot prot,
+ enum kvm_pgtable_prot required,
+ enum kvm_pgtable_prot denied)
+{
+ return (prot & (required | denied)) == required;
+}
+
+int __pkvm_host_share_hyp(u64 pfn)
+{
+ phys_addr_t addr = hyp_pfn_to_phys(pfn);
+ enum kvm_pgtable_prot prot, cur;
+ void *virt = __hyp_va(addr);
+ enum pkvm_page_state state;
+ kvm_pte_t pte;
+ u32 level;
+ int ret;
+
+ if (!range_is_memory(addr, addr + PAGE_SIZE))
+ return -EINVAL;
+
+ hyp_spin_lock(&host_kvm.lock);
+ hyp_spin_lock(&pkvm_pgd_lock);
+
+ ret = kvm_pgtable_get_leaf(&host_kvm.pgt, addr, &pte, &level);
+ if (ret)
+ goto unlock;
+ if (!pte)
+ goto map_shared;
+
+ /*
+ * Check attributes in the host stage-2 PTE. We need the page to be:
+ * - mapped RWX as we're sharing memory;
+ * - not borrowed, as that implies absence of ownership.
+ * Otherwise, we can't let it got through
+ */
+ cur = kvm_pgtable_stage2_pte_prot(pte);
+ prot = pkvm_mkstate(0, PKVM_PAGE_SHARED_BORROWED);
+ if (!check_prot(cur, KVM_PGTABLE_PROT_RWX, prot)) {
+ ret = -EPERM;
+ goto unlock;
+ }
+
+ state = pkvm_getstate(cur);
+ if (state == PKVM_PAGE_OWNED)
+ goto map_shared;
+
+ /*
+ * Tolerate double-sharing the same page, but this requires
+ * cross-checking the hypervisor stage-1.
+ */
+ if (state != PKVM_PAGE_SHARED_OWNED) {
+ ret = -EPERM;
+ goto unlock;
+ }
+
+ ret = kvm_pgtable_get_leaf(&pkvm_pgtable, (u64)virt, &pte, &level);
+ if (ret)
+ goto unlock;
+
+ /*
+ * If the page has been shared with the hypervisor, it must be
+ * SHARED_BORROWED already.
+ */
+ cur = kvm_pgtable_hyp_pte_prot(pte);
+ prot = pkvm_mkstate(PAGE_HYP, PKVM_PAGE_SHARED_BORROWED);
+ if (!check_prot(cur, prot, ~prot))
+ ret = EPERM;
+ goto unlock;
+
+map_shared:
+ /*
+ * If the page is not yet shared, adjust mappings in both page-tables
+ * while both locks are held.
+ */
+ prot = pkvm_mkstate(PAGE_HYP, PKVM_PAGE_SHARED_BORROWED);
+ ret = pkvm_create_mappings_locked(virt, virt + PAGE_SIZE, prot);
+ BUG_ON(ret);
+
+ prot = pkvm_mkstate(KVM_PGTABLE_PROT_RWX, PKVM_PAGE_SHARED_OWNED);
+ ret = host_stage2_idmap_locked(addr, addr + PAGE_SIZE, prot);
+ BUG_ON(ret);
+
+unlock:
+ hyp_spin_unlock(&pkvm_pgd_lock);
+ hyp_spin_unlock(&host_kvm.lock);
+
+ return ret;
+}
+
void handle_host_mem_abort(struct kvm_cpu_context *host_ctxt)
{
struct kvm_vcpu_fault_info fault;
diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
index 0625bf2353c2..cbab146cda6a 100644
--- a/arch/arm64/kvm/mmu.c
+++ b/arch/arm64/kvm/mmu.c
@@ -259,10 +259,8 @@ static int __create_hyp_mappings(unsigned long start, unsigned long size,
{
int err;
- if (!kvm_host_owns_hyp_mappings()) {
- return kvm_call_hyp_nvhe(__pkvm_create_mappings,
- start, size, phys, prot);
- }
+ if (WARN_ON(!kvm_host_owns_hyp_mappings()))
+ return -EINVAL;
mutex_lock(&kvm_hyp_pgd_mutex);
err = kvm_pgtable_hyp_map(hyp_pgtable, start, size, phys, prot);
@@ -282,6 +280,21 @@ static phys_addr_t kvm_kaddr_to_phys(void *kaddr)
}
}
+static int pkvm_share_hyp(phys_addr_t start, phys_addr_t end)
+{
+ phys_addr_t addr;
+ int ret;
+
+ for (addr = ALIGN_DOWN(start, PAGE_SIZE); addr < end; addr += PAGE_SIZE) {
+ ret = kvm_call_hyp_nvhe(__pkvm_host_share_hyp,
+ __phys_to_pfn(addr));
+ if (ret)
+ return ret;
+ }
+
+ return 0;
+}
+
/**
* create_hyp_mappings - duplicate a kernel virtual address range in Hyp mode
* @from: The virtual kernel start address of the range
@@ -302,6 +315,13 @@ int create_hyp_mappings(void *from, void *to, enum kvm_pgtable_prot prot)
if (is_kernel_in_hyp_mode())
return 0;
+ if (!kvm_host_owns_hyp_mappings()) {
+ if (WARN_ON(prot != PAGE_HYP))
+ return -EPERM;
+ return pkvm_share_hyp(kvm_kaddr_to_phys(from),
+ kvm_kaddr_to_phys(to));
+ }
+
start = start & PAGE_MASK;
end = PAGE_ALIGN(end);
--
2.32.0.432.gabb21c7263-goog
next prev parent reply other threads:[~2021-07-29 13:29 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-29 13:27 [PATCH v3 00/21] Track shared pages at EL2 in protected mode Quentin Perret
2021-07-29 13:27 ` [PATCH v3 01/21] KVM: arm64: Add hyp_spin_is_locked() for basic locking assertions at EL2 Quentin Perret
2021-07-29 13:27 ` [PATCH v3 02/21] KVM: arm64: Introduce hyp_assert_lock_held() Quentin Perret
2021-07-29 13:28 ` [PATCH v3 03/21] KVM: arm64: Provide the host_stage2_try() helper macro Quentin Perret
2021-08-02 9:36 ` Fuad Tabba
2021-07-29 13:28 ` [PATCH v3 04/21] KVM: arm64: Introduce helper to retrieve a PTE and its level Quentin Perret
2021-07-29 13:28 ` [PATCH v3 05/21] KVM: arm64: Expose page-table helpers Quentin Perret
2021-07-29 13:28 ` [PATCH v3 06/21] KVM: arm64: Optimize host memory aborts Quentin Perret
2021-08-02 9:37 ` Fuad Tabba
2021-07-29 13:28 ` [PATCH v3 07/21] KVM: arm64: Rename KVM_PTE_LEAF_ATTR_S2_IGNORED Quentin Perret
2021-08-02 9:37 ` Fuad Tabba
2021-07-29 13:28 ` [PATCH v3 08/21] KVM: arm64: Don't overwrite software bits with owner id Quentin Perret
2021-08-02 9:38 ` Fuad Tabba
2021-07-29 13:28 ` [PATCH v3 09/21] KVM: arm64: Tolerate re-creating hyp mappings to set software bits Quentin Perret
2021-08-02 9:50 ` Fuad Tabba
2021-07-29 13:28 ` [PATCH v3 10/21] KVM: arm64: Enable forcing page-level stage-2 mappings Quentin Perret
2021-08-02 9:49 ` Fuad Tabba
2021-08-03 10:13 ` Quentin Perret
2021-08-03 10:43 ` Fuad Tabba
2021-07-29 13:28 ` [PATCH v3 11/21] KVM: arm64: Allow populating software bits Quentin Perret
2021-07-29 13:28 ` [PATCH v3 12/21] KVM: arm64: Add helpers to tag shared pages in SW bits Quentin Perret
2021-08-02 10:30 ` Fuad Tabba
2021-07-29 13:28 ` [PATCH v3 13/21] KVM: arm64: Expose host stage-2 manipulation helpers Quentin Perret
2021-08-02 11:13 ` Fuad Tabba
2021-08-03 10:20 ` Quentin Perret
2021-07-29 13:28 ` [PATCH v3 14/21] KVM: arm64: Expose pkvm_hyp_id Quentin Perret
2021-07-29 13:28 ` [PATCH v3 15/21] KVM: arm64: Introduce addr_is_memory() Quentin Perret
2021-08-02 14:52 ` Fuad Tabba
2021-08-03 10:23 ` Quentin Perret
2021-07-29 13:28 ` [PATCH v3 16/21] KVM: arm64: Enable retrieving protections attributes of PTEs Quentin Perret
2021-08-02 14:52 ` Fuad Tabba
2021-08-03 10:24 ` Quentin Perret
2021-07-29 13:28 ` [PATCH v3 17/21] KVM: arm64: Mark host bss and rodata section as shared Quentin Perret
2021-08-03 5:02 ` Fuad Tabba
2021-08-03 10:34 ` Quentin Perret
2021-08-03 10:54 ` Fuad Tabba
2021-07-29 13:28 ` [PATCH v3 18/21] KVM: arm64: Remove __pkvm_mark_hyp Quentin Perret
2021-07-29 13:28 ` [PATCH v3 19/21] KVM: arm64: Refactor protected nVHE stage-1 locking Quentin Perret
2021-08-03 5:31 ` Fuad Tabba
2021-08-03 10:37 ` Quentin Perret
2021-08-03 10:51 ` Fuad Tabba
2021-07-29 13:28 ` Quentin Perret [this message]
2021-08-03 8:22 ` [PATCH v3 20/21] KVM: arm64: Restrict EL2 stage-1 changes in protected mode Fuad Tabba
2021-08-03 10:43 ` Quentin Perret
2021-07-29 13:28 ` [PATCH v3 21/21] KVM: arm64: Make __pkvm_create_mappings static Quentin Perret
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