On 11.11.2021 16.13, Chao Peng wrote:
Currently support to exit to userspace for private/shared memory
conversion.
Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
Signed-off-by: Yu Zhang <yu.c.zhang@xxxxxxxxxxxxxxx>
Signed-off-by: Chao Peng <chao.p.peng@xxxxxxxxxxxxxxx>
---
arch/x86/kvm/mmu/mmu.c | 20 ++++++++++++++++++++
include/uapi/linux/kvm.h | 15 +++++++++++++++
2 files changed, 35 insertions(+)
diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index af5ecf4ef62a..780868888aa8 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -3950,6 +3950,17 @@ static bool try_async_pf(struct kvm_vcpu *vcpu, bool prefault, gfn_t gfn,
slot = __kvm_vcpu_gfn_to_memslot(vcpu, gfn, private);
+ /*
+ * Exit to userspace to map the requested private/shared memory region
+ * if there is no memslot and (a) the access is private or (b) there is
+ * an existing private memslot. Emulated MMIO must be accessed through
+ * shared GPAs, thus a memslot miss on a private GPA is always handled
+ * as an implicit conversion "request".
+ */
+ if (!slot &&
+ (private || __kvm_vcpu_gfn_to_memslot(vcpu, gfn, true)))
+ goto out_convert;
+
/* Don't expose aliases for no slot GFNs or private memslots */
if ((cr2_or_gpa & vcpu_gpa_stolen_mask(vcpu)) &&
!kvm_is_visible_memslot(slot)) {
@@ -3994,6 +4005,15 @@ static bool try_async_pf(struct kvm_vcpu *vcpu, bool prefault, gfn_t gfn,
*pfn = __gfn_to_pfn_memslot(slot, gfn, false, NULL,
write, writable, hva);
return false;
+
+out_convert:
+ vcpu->run->exit_reason = KVM_EXIT_MEMORY_ERROR;
+ vcpu->run->mem.type = private ? KVM_EXIT_MEM_MAP_PRIVATE
+ : KVM_EXIT_MEM_MAP_SHARE;
+ vcpu->run->mem.u.map.gpa = cr2_or_gpa;
+ vcpu->run->mem.u.map.size = PAGE_SIZE;
+ return true;
+
I think this does just retry, no exit to user space?
}
static int direct_page_fault(struct kvm_vcpu *vcpu, gpa_t gpa, u32 error_code,
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index 8d20caae9180..470c472a9451 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -233,6 +233,18 @@ struct kvm_xen_exit {
} u;
};
+struct kvm_memory_exit {
+#define KVM_EXIT_MEM_MAP_SHARE 1
+#define KVM_EXIT_MEM_MAP_PRIVATE 2
+ __u32 type;
+ union {
+ struct {
+ __u64 gpa;
+ __u64 size;
+ } map;
+ } u;
+};
+
#define KVM_S390_GET_SKEYS_NONE 1
#define KVM_S390_SKEYS_MAX 1048576
@@ -272,6 +284,7 @@ struct kvm_xen_exit {
#define KVM_EXIT_X86_BUS_LOCK 33
#define KVM_EXIT_XEN 34
#define KVM_EXIT_TDVMCALL 35
+#define KVM_EXIT_MEMORY_ERROR 36
/* For KVM_EXIT_INTERNAL_ERROR */
/* Emulate instruction failed. */
@@ -455,6 +468,8 @@ struct kvm_run {
__u64 subfunc;
__u64 param[4];
} tdvmcall;
+ /* KVM_EXIT_MEMORY_ERROR */
+ struct kvm_memory_exit mem;
/* Fix the size of the union. */
char padding[256];
};
