From: Liran Alon <liran.alon@xxxxxxxxxx>
Create a separate mm for KVM that will be active when KVM #VMExit
handlers run. Up until the point which we architectully need to
access host (or other VM) sensitive data.
This patch just create kvm_mm but never makes it active yet.
This will be done by next commits.
Signed-off-by: Liran Alon <liran.alon@xxxxxxxxxx>
Signed-off-by: Alexandre Chartre <alexandre.chartre@xxxxxxxxxx>
---
arch/x86/kvm/isolation.c | 95 ++++++++++++++++++++++++++++++++++++++++++++++
arch/x86/kvm/isolation.h | 8 ++++
arch/x86/kvm/x86.c | 10 ++++-
3 files changed, 112 insertions(+), 1 deletions(-)
create mode 100644 arch/x86/kvm/isolation.h
diff --git a/arch/x86/kvm/isolation.c b/arch/x86/kvm/isolation.c
index e25f663..74bc0cd 100644
--- a/arch/x86/kvm/isolation.c
+++ b/arch/x86/kvm/isolation.c
@@ -7,6 +7,21 @@
#include <linux/module.h>
#include <linux/moduleparam.h>
+#include <linux/printk.h>
+
+#include <asm/mmu_context.h>
+#include <asm/pgalloc.h>
+
+#include "isolation.h"
+
+struct mm_struct kvm_mm = {
+ .mm_rb = RB_ROOT,
+ .mm_users = ATOMIC_INIT(2),
+ .mm_count = ATOMIC_INIT(1),
+ .mmap_sem = __RWSEM_INITIALIZER(kvm_mm.mmap_sem),
+ .page_table_lock = __SPIN_LOCK_UNLOCKED(kvm_mm.page_table_lock),
+ .mmlist = LIST_HEAD_INIT(kvm_mm.mmlist),
+};
/*
* When set to true, KVM #VMExit handlers run in isolated address space
@@ -24,3 +39,83 @@
*/
static bool __read_mostly address_space_isolation;
module_param(address_space_isolation, bool, 0444);
+
+static int kvm_isolation_init_mm(void)
+{
+ pgd_t *kvm_pgd;
+ gfp_t gfp_mask;
+
+ gfp_mask = GFP_KERNEL | __GFP_ZERO;
+ kvm_pgd = (pgd_t *)__get_free_pages(gfp_mask, PGD_ALLOCATION_ORDER);
+ if (!kvm_pgd)
+ return -ENOMEM;
+
+#ifdef CONFIG_PAGE_TABLE_ISOLATION
+ /*
+ * With PTI, we have two PGDs: one the kernel page table, and one
+ * for the user page table. The PGD with the kernel page table has
+ * to be the entire kernel address space because paranoid faults
+ * will unconditionally use it. So we define the KVM address space
+ * in the user table space, although it will be used in the kernel.
+ */
+
+ /* initialize the kernel page table */
+ memcpy(kvm_pgd, current->active_mm->pgd, sizeof(pgd_t) * PTRS_PER_PGD);
+
+ /* define kvm_mm with the user page table */
+ kvm_mm.pgd = kernel_to_user_pgdp(kvm_pgd);
+#else /* CONFIG_PAGE_TABLE_ISOLATION */
+ kvm_mm.pgd = kvm_pgd;
+#endif /* CONFIG_PAGE_TABLE_ISOLATION */
+ mm_init_cpumask(&kvm_mm);
+ init_new_context(NULL, &kvm_mm);
+
+ return 0;
+}
+
+static void kvm_isolation_uninit_mm(void)
+{
+ pgd_t *kvm_pgd;
+
+ BUG_ON(current->active_mm == &kvm_mm);
+
+ destroy_context(&kvm_mm);
+
+#ifdef CONFIG_PAGE_TABLE_ISOLATION
+ /*
+ * With PTI, the KVM address space is defined in the user
+ * page table space, but the full PGD starts with the kernel
+ * page table space.
+ */
+ kvm_pgd = user_to_kernel_pgdp(kvm_pgd);
+#else /* CONFIG_PAGE_TABLE_ISOLATION */
+ kvm_pgd = kvm_mm.pgd;
+#endif /* CONFIG_PAGE_TABLE_ISOLATION */
+ kvm_mm.pgd = NULL;
+ free_pages((unsigned long)kvm_pgd, PGD_ALLOCATION_ORDER);
+}
+
+int kvm_isolation_init(void)
+{
+ int r;
+
+ if (!address_space_isolation)
+ return 0;
+
+ r = kvm_isolation_init_mm();
+ if (r)
+ return r;
+
+ pr_info("KVM: x86: Running with isolated address space\n");
+
+ return 0;
+}
+
+void kvm_isolation_uninit(void)
+{
+ if (!address_space_isolation)
+ return;
+
+ kvm_isolation_uninit_mm();
+ pr_info("KVM: x86: End of isolated address space\n");
+}
diff --git a/arch/x86/kvm/isolation.h b/arch/x86/kvm/isolation.h
new file mode 100644
index 0000000..cf8c7d4
--- /dev/null
+++ b/arch/x86/kvm/isolation.h
@@ -0,0 +1,8 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef ARCH_X86_KVM_ISOLATION_H
+#define ARCH_X86_KVM_ISOLATION_H
+
+extern int kvm_isolation_init(void);
+extern void kvm_isolation_uninit(void);
+
+#endif
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index b5edc8e..4b7cec2 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -29,6 +29,7 @@
#include "cpuid.h"
#include "pmu.h"
#include "hyperv.h"
+#include "isolation.h"
#include <linux/clocksource.h>
#include <linux/interrupt.h>
@@ -6972,10 +6973,14 @@ int kvm_arch_init(void *opaque)
goto out_free_x86_fpu_cache;
}
- r = kvm_mmu_module_init();
+ r = kvm_isolation_init();
if (r)
goto out_free_percpu;
+ r = kvm_mmu_module_init();
+ if (r)
+ goto out_uninit_isolation;
+
kvm_set_mmio_spte_mask();
kvm_x86_ops = ops;
@@ -7000,6 +7005,8 @@ int kvm_arch_init(void *opaque)
return 0;
+out_uninit_isolation:
+ kvm_isolation_uninit();
out_free_percpu:
free_percpu(shared_msrs);
out_free_x86_fpu_cache:
@@ -7024,6 +7031,7 @@ void kvm_arch_exit(void)
#ifdef CONFIG_X86_64
pvclock_gtod_unregister_notifier(&pvclock_gtod_notifier);
#endif
+ kvm_isolation_uninit();
kvm_x86_ops = NULL;
kvm_mmu_module_exit();
free_percpu(shared_msrs);
--
1.7.1
