From: Chao Peng <[email protected]>
This new KVM exit allows userspace to handle memory-related errors. It
indicates an error happens in KVM at guest memory range [gpa, gpa+size).
The flags includes additional information for userspace to handle the
error. Currently bit 0 is defined as 'private memory' where '1'
indicates error happens due to private memory access and '0' indicates
error happens due to shared memory access.
When private memory is enabled, this new exit will be used for KVM to
exit to userspace for shared <-> private memory conversion in memory
encryption usage. In such usage, typically there are two kind of memory
conversions:
- explicit conversion: happens when guest explicitly calls into KVM
to map a range (as private or shared), KVM then exits to userspace
to perform the map/unmap operations.
- implicit conversion: happens in KVM page fault handler where KVM
exits to userspace for an implicit conversion when the page is in a
different state than requested (private or shared).
Suggested-by: Sean Christopherson <[email protected]>
Co-developed-by: Yu Zhang <[email protected]>
Signed-off-by: Yu Zhang <[email protected]>
Signed-off-by: Chao Peng <[email protected]>
Reviewed-by: Fuad Tabba <[email protected]>
Tested-by: Fuad Tabba <[email protected]>
Signed-off-by: Sean Christopherson <[email protected]>
---
Documentation/virt/kvm/api.rst | 22 ++++++++++++++++++++++
include/uapi/linux/kvm.h | 8 ++++++++
2 files changed, 30 insertions(+)
diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
index c0ddd3035462..34d4ce66e0c8 100644
--- a/Documentation/virt/kvm/api.rst
+++ b/Documentation/virt/kvm/api.rst
@@ -6700,6 +6700,28 @@ array field represents return values. The userspace should update the return
values of SBI call before resuming the VCPU. For more details on RISC-V SBI
spec refer, https://github.com/riscv/riscv-sbi-doc.
+::
+
+ /* KVM_EXIT_MEMORY_FAULT */
+ struct {
+ #define KVM_MEMORY_EXIT_FLAG_PRIVATE (1ULL << 3)
+ __u64 flags;
+ __u64 gpa;
+ __u64 size;
+ } memory;
+
+If exit reason is KVM_EXIT_MEMORY_FAULT then it indicates that the VCPU has
+encountered a memory error which is not handled by KVM kernel module and
+userspace may choose to handle it. The 'flags' field indicates the memory
+properties of the exit.
+
+ - KVM_MEMORY_EXIT_FLAG_PRIVATE - indicates the memory error is caused by
+ private memory access when the bit is set. Otherwise the memory error is
+ caused by shared memory access when the bit is clear.
+
+'gpa' and 'size' indicate the memory range the error occurs at. The userspace
+may handle the error and return to KVM to retry the previous memory access.
+
::
/* KVM_EXIT_NOTIFY */
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index 4d4b3de8ac55..6c6ed214b6ac 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -274,6 +274,7 @@ struct kvm_xen_exit {
#define KVM_EXIT_RISCV_SBI 35
#define KVM_EXIT_RISCV_CSR 36
#define KVM_EXIT_NOTIFY 37
+#define KVM_EXIT_MEMORY_FAULT 38
/* For KVM_EXIT_INTERNAL_ERROR */
/* Emulate instruction failed. */
@@ -520,6 +521,13 @@ struct kvm_run {
#define KVM_NOTIFY_CONTEXT_INVALID (1 << 0)
__u32 flags;
} notify;
+ /* KVM_EXIT_MEMORY_FAULT */
+ struct {
+#define KVM_MEMORY_EXIT_FLAG_PRIVATE (1ULL << 3)
+ __u64 flags;
+ __u64 gpa;
+ __u64 size;
+ } memory;
/* Fix the size of the union. */
char padding[256];
};
--
2.41.0.255.g8b1d071c50-goog
On Tue, Jul 18, 2023 at 04:44:50PM -0700, Sean Christopherson wrote:
> From: Chao Peng <[email protected]>
>
> This new KVM exit allows userspace to handle memory-related errors. It
> indicates an error happens in KVM at guest memory range [gpa, gpa+size).
> The flags includes additional information for userspace to handle the
> error. Currently bit 0 is defined as 'private memory' where '1'
> indicates error happens due to private memory access and '0' indicates
> error happens due to shared memory access.
Now it's bit 3:
#define KVM_MEMORY_EXIT_FLAG_PRIVATE (1ULL << 3)
I remember some other attributes were introduced in v10 yet:
#define KVM_MEMORY_ATTRIBUTE_READ (1ULL << 0)
#define KVM_MEMORY_ATTRIBUTE_WRITE (1ULL << 1)
#define KVM_MEMORY_ATTRIBUTE_EXECUTE (1ULL << 2)
#define KVM_MEMORY_ATTRIBUTE_PRIVATE (1ULL << 3)
So KVM_MEMORY_EXIT_FLAG_PRIVATE changed to bit 3 due to above things,
or other reason ? (Sorry I didn't follow v10 too much before).
>
> When private memory is enabled, this new exit will be used for KVM to
> exit to userspace for shared <-> private memory conversion in memory
> encryption usage. In such usage, typically there are two kind of memory
> conversions:
> - explicit conversion: happens when guest explicitly calls into KVM
> to map a range (as private or shared), KVM then exits to userspace
> to perform the map/unmap operations.
> - implicit conversion: happens in KVM page fault handler where KVM
> exits to userspace for an implicit conversion when the page is in a
> different state than requested (private or shared).
>
> Suggested-by: Sean Christopherson <[email protected]>
> Co-developed-by: Yu Zhang <[email protected]>
> Signed-off-by: Yu Zhang <[email protected]>
> Signed-off-by: Chao Peng <[email protected]>
> Reviewed-by: Fuad Tabba <[email protected]>
> Tested-by: Fuad Tabba <[email protected]>
> Signed-off-by: Sean Christopherson <[email protected]>
> ---
> Documentation/virt/kvm/api.rst | 22 ++++++++++++++++++++++
> include/uapi/linux/kvm.h | 8 ++++++++
> 2 files changed, 30 insertions(+)
>
> diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
> index c0ddd3035462..34d4ce66e0c8 100644
> --- a/Documentation/virt/kvm/api.rst
> +++ b/Documentation/virt/kvm/api.rst
> @@ -6700,6 +6700,28 @@ array field represents return values. The userspace should update the return
> values of SBI call before resuming the VCPU. For more details on RISC-V SBI
> spec refer, https://github.com/riscv/riscv-sbi-doc.
>
> +::
> +
> + /* KVM_EXIT_MEMORY_FAULT */
> + struct {
> + #define KVM_MEMORY_EXIT_FLAG_PRIVATE (1ULL << 3)
> + __u64 flags;
> + __u64 gpa;
> + __u64 size;
> + } memory;
> +
> +If exit reason is KVM_EXIT_MEMORY_FAULT then it indicates that the VCPU has
> +encountered a memory error which is not handled by KVM kernel module and
> +userspace may choose to handle it. The 'flags' field indicates the memory
> +properties of the exit.
> +
> + - KVM_MEMORY_EXIT_FLAG_PRIVATE - indicates the memory error is caused by
> + private memory access when the bit is set. Otherwise the memory error is
> + caused by shared memory access when the bit is clear.
> +
> +'gpa' and 'size' indicate the memory range the error occurs at. The userspace
> +may handle the error and return to KVM to retry the previous memory access.
> +
> ::
>
> /* KVM_EXIT_NOTIFY */
> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> index 4d4b3de8ac55..6c6ed214b6ac 100644
> --- a/include/uapi/linux/kvm.h
> +++ b/include/uapi/linux/kvm.h
> @@ -274,6 +274,7 @@ struct kvm_xen_exit {
> #define KVM_EXIT_RISCV_SBI 35
> #define KVM_EXIT_RISCV_CSR 36
> #define KVM_EXIT_NOTIFY 37
> +#define KVM_EXIT_MEMORY_FAULT 38
>
> /* For KVM_EXIT_INTERNAL_ERROR */
> /* Emulate instruction failed. */
> @@ -520,6 +521,13 @@ struct kvm_run {
> #define KVM_NOTIFY_CONTEXT_INVALID (1 << 0)
> __u32 flags;
> } notify;
> + /* KVM_EXIT_MEMORY_FAULT */
> + struct {
> +#define KVM_MEMORY_EXIT_FLAG_PRIVATE (1ULL << 3)
> + __u64 flags;
> + __u64 gpa;
> + __u64 size;
> + } memory;
> /* Fix the size of the union. */
> char padding[256];
> };
> --
> 2.41.0.255.g8b1d071c50-goog
>
On Wed, Jul 19, 2023, Yuan Yao wrote:
> On Tue, Jul 18, 2023 at 04:44:50PM -0700, Sean Christopherson wrote:
> > From: Chao Peng <[email protected]>
> >
> > This new KVM exit allows userspace to handle memory-related errors. It
> > indicates an error happens in KVM at guest memory range [gpa, gpa+size).
> > The flags includes additional information for userspace to handle the
> > error. Currently bit 0 is defined as 'private memory' where '1'
> > indicates error happens due to private memory access and '0' indicates
> > error happens due to shared memory access.
>
> Now it's bit 3:
Yeah, I need to update (or write) a lot of changelogs.
> #define KVM_MEMORY_EXIT_FLAG_PRIVATE (1ULL << 3)
>
> I remember some other attributes were introduced in v10 yet:
>
> #define KVM_MEMORY_ATTRIBUTE_READ (1ULL << 0)
> #define KVM_MEMORY_ATTRIBUTE_WRITE (1ULL << 1)
> #define KVM_MEMORY_ATTRIBUTE_EXECUTE (1ULL << 2)
> #define KVM_MEMORY_ATTRIBUTE_PRIVATE (1ULL << 3)
>
> So KVM_MEMORY_EXIT_FLAG_PRIVATE changed to bit 3 due to above things,
> or other reason ? (Sorry I didn't follow v10 too much before).
Yep, I want to reserve space for the RWX bits.