Commit 1050dcda30529 introduced KVM_MEMSLOT_INCOHERENT to flag memory
regions that may have coherency issues due to mapping host system RAM
as non-cacheable. This was introduced as a KVM internal flag, but now
give KVM userspace access to it so that it may use it for hinting
likely problematic regions. Also rename to KVM_MEM_UNCACHED.
Signed-off-by: Andrew Jones <drjones@xxxxxxxxxx>
---
Documentation/virtual/kvm/api.txt | 20 ++++++++++++++------
arch/arm/include/uapi/asm/kvm.h | 1 +
arch/arm/kvm/arm.c | 1 +
arch/arm/kvm/mmu.c | 4 ++--
arch/arm64/include/uapi/asm/kvm.h | 1 +
include/linux/kvm_host.h | 1 -
include/uapi/linux/kvm.h | 2 ++
virt/kvm/kvm_main.c | 7 ++++++-
8 files changed, 27 insertions(+), 10 deletions(-)
diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
index 9fa2bf8c3f6f1..04ffd9f5db5f2 100644
--- a/Documentation/virtual/kvm/api.txt
+++ b/Documentation/virtual/kvm/api.txt
@@ -905,6 +905,7 @@ struct kvm_userspace_memory_region {
/* for kvm_memory_region::flags */
#define KVM_MEM_LOG_DIRTY_PAGES (1UL << 0)
#define KVM_MEM_READONLY (1UL << 1)
+#define KVM_MEM_UNCACHED (1UL << 2)
This ioctl allows the user to create or modify a guest physical memory
slot. When changing an existing slot, it may be moved in the guest
@@ -920,12 +921,19 @@ It is recommended that the lower 21 bits of guest_phys_addr and userspace_addr
be identical. This allows large pages in the guest to be backed by large
pages in the host.
-The flags field supports two flags: KVM_MEM_LOG_DIRTY_PAGES and
-KVM_MEM_READONLY. The former can be set to instruct KVM to keep track of
-writes to memory within the slot. See KVM_GET_DIRTY_LOG ioctl to know how to
-use it. The latter can be set, if KVM_CAP_READONLY_MEM capability allows it,
-to make a new slot read-only. In this case, writes to this memory will be
-posted to userspace as KVM_EXIT_MMIO exits.
+The flags field supports the following flags. All flags may be used in
+combination.
+ - KVM_MEM_LOG_DIRTY_PAGES: no capability required
+ Set this to instruct KVM to keep track of writes to memory within
+ the slot. (See the KVM_GET_DIRTY_LOG ioctl)
+ - KVM_MEM_READONLY: depends on capability KVM_CAP_READONLY_MEM
+ Set this to make a new slot read-only. In this case, writes to
+ this memory will be posted to userspace as KVM_EXIT_MMIO exits.
+ EINVAL will be returned if the slot is not new.
+ - KVM_MEM_UNCACHED: depends on capability KVM_CAP_UNCACHED_MEM
+ Set this to make a new slot uncached, i.e. userspace will always
+ directly read/write RAM for this memory region. EINVAL will be
+ returned if the slot is not new.
When the KVM_CAP_SYNC_MMU capability is available, changes in the backing of
the memory region are automatically reflected into the guest. For example, an
diff --git a/arch/arm/include/uapi/asm/kvm.h b/arch/arm/include/uapi/asm/kvm.h
index df3f60cb1168a..893a331655115 100644
--- a/arch/arm/include/uapi/asm/kvm.h
+++ b/arch/arm/include/uapi/asm/kvm.h
@@ -26,6 +26,7 @@
#define __KVM_HAVE_GUEST_DEBUG
#define __KVM_HAVE_IRQ_LINE
#define __KVM_HAVE_READONLY_MEM
+#define __KVM_HAVE_UNCACHED_MEM
#define KVM_REG_SIZE(id) \
(1U << (((id) & KVM_REG_SIZE_MASK) >> KVM_REG_SIZE_SHIFT))
diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c
index d9631ecddd56e..cbb532de9c8b5 100644
--- a/arch/arm/kvm/arm.c
+++ b/arch/arm/kvm/arm.c
@@ -182,6 +182,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
case KVM_CAP_ARM_PSCI_0_2:
case KVM_CAP_READONLY_MEM:
case KVM_CAP_MP_STATE:
+ case KVM_CAP_UNCACHED_MEM:
r = 1;
break;
case KVM_CAP_COALESCED_MMIO:
diff --git a/arch/arm/kvm/mmu.c b/arch/arm/kvm/mmu.c
index 1d5accbd3dcf2..bc1665acd73e7 100644
--- a/arch/arm/kvm/mmu.c
+++ b/arch/arm/kvm/mmu.c
@@ -1307,7 +1307,7 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
if (!hugetlb && !force_pte)
hugetlb = transparent_hugepage_adjust(&pfn, &fault_ipa);
- fault_ipa_uncached = memslot->flags & KVM_MEMSLOT_INCOHERENT;
+ fault_ipa_uncached = memslot->flags & KVM_MEM_UNCACHED;
if (hugetlb) {
pmd_t new_pmd = pfn_pmd(pfn, mem_type);
@@ -1834,7 +1834,7 @@ int kvm_arch_create_memslot(struct kvm *kvm, struct kvm_memory_slot *slot,
* regions as incoherent.
*/
if (slot->flags & KVM_MEM_READONLY)
- slot->flags |= KVM_MEMSLOT_INCOHERENT;
+ slot->flags |= KVM_MEM_UNCACHED;
return 0;
}
diff --git a/arch/arm64/include/uapi/asm/kvm.h b/arch/arm64/include/uapi/asm/kvm.h
index d26832022127e..be46855ca01b7 100644
--- a/arch/arm64/include/uapi/asm/kvm.h
+++ b/arch/arm64/include/uapi/asm/kvm.h
@@ -38,6 +38,7 @@
#define __KVM_HAVE_GUEST_DEBUG
#define __KVM_HAVE_IRQ_LINE
#define __KVM_HAVE_READONLY_MEM
+#define __KVM_HAVE_UNCACHED_MEM
#define KVM_REG_SIZE(id) \
(1U << (((id) & KVM_REG_SIZE_MASK) >> KVM_REG_SIZE_SHIFT))
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index ad45054309a0f..74d6a14529f53 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -39,7 +39,6 @@
* include/linux/kvm_h.
*/
#define KVM_MEMSLOT_INVALID (1UL << 16)
-#define KVM_MEMSLOT_INCOHERENT (1UL << 17)
/* Two fragments for cross MMIO pages. */
#define KVM_MAX_MMIO_FRAGMENTS 2
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index 4b60056776d14..ceb6e805e5f77 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -108,6 +108,7 @@ struct kvm_userspace_memory_region {
*/
#define KVM_MEM_LOG_DIRTY_PAGES (1UL << 0)
#define KVM_MEM_READONLY (1UL << 1)
+#define KVM_MEM_UNCACHED (1UL << 2)
/* for KVM_IRQ_LINE */
struct kvm_irq_level {
@@ -814,6 +815,7 @@ struct kvm_ppc_smmu_info {
#define KVM_CAP_S390_INJECT_IRQ 113
#define KVM_CAP_S390_IRQ_STATE 114
#define KVM_CAP_PPC_HWRNG 115
+#define KVM_CAP_UNCACHED_MEM 116
#ifdef KVM_CAP_IRQ_ROUTING
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 90977418aeb6e..d1d535d80a075 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -719,6 +719,10 @@ static int check_memory_region_flags(struct kvm_userspace_memory_region *mem)
valid_flags |= KVM_MEM_READONLY;
#endif
+#ifdef __KVM_HAVE_UNCACHED_MEM
+ valid_flags |= KVM_MEM_UNCACHED;
+#endif
+
if (mem->flags & ~valid_flags)
return -EINVAL;
@@ -816,7 +820,8 @@ int __kvm_set_memory_region(struct kvm *kvm,
else { /* Modify an existing slot. */
if ((mem->userspace_addr != old.userspace_addr) ||
(npages != old.npages) ||
- ((new.flags ^ old.flags) & KVM_MEM_READONLY))
+ ((new.flags ^ old.flags) &
+ (KVM_MEM_READONLY | KVM_MEM_UNCACHED)))
goto out;
if (base_gfn != old.base_gfn)
--
2.1.0
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