Re: [PATCH 10/25] KVM: TDX: Initialize KVM supported capabilities when module setup
From: Xiaoyao Li
Date: Thu Sep 12 2024 - 04:37:24 EST
On 9/12/2024 4:04 PM, Nikolay Borisov wrote:
On 5.09.24 г. 16:36 ч., Xiaoyao Li wrote:
On 9/4/2024 7:58 PM, Nikolay Borisov wrote:
On 13.08.24 г. 1:48 ч., Rick Edgecombe wrote:
From: Xiaoyao Li <xiaoyao.li@xxxxxxxxx>
While TDX module reports a set of capabilities/features that it
supports, what KVM currently supports might be a subset of them.
E.g., DEBUG and PERFMON are supported by TDX module but currently not
supported by KVM.
Introduce a new struct kvm_tdx_caps to store KVM's capabilities of TDX.
supported_attrs and suppported_xfam are validated against fixed0/1
values enumerated by TDX module. Configurable CPUID bits derive from
TDX
module plus applying KVM's capabilities (KVM_GET_SUPPORTED_CPUID),
i.e., mask off the bits that are configurable in the view of TDX module
but not supported by KVM yet.
KVM_TDX_CPUID_NO_SUBLEAF is the concept from TDX module, switch it to 0
and use KVM_CPUID_FLAG_SIGNIFCANT_INDEX, which are the concept of KVM.
Signed-off-by: Xiaoyao Li <xiaoyao.li@xxxxxxxxx>
Signed-off-by: Rick Edgecombe <rick.p.edgecombe@xxxxxxxxx>
---
uAPI breakout v1:
- Change setup_kvm_tdx_caps() to use the exported 'struct
tdx_sysinfo'
pointer.
- Change how to copy 'kvm_tdx_cpuid_config' since 'struct
tdx_sysinfo'
doesn't have 'kvm_tdx_cpuid_config'.
- Updates for uAPI changes
---
arch/x86/include/uapi/asm/kvm.h | 2 -
arch/x86/kvm/vmx/tdx.c | 81
+++++++++++++++++++++++++++++++++
2 files changed, 81 insertions(+), 2 deletions(-)
diff --git a/arch/x86/include/uapi/asm/kvm.h
b/arch/x86/include/uapi/asm/kvm.h
index 47caf508cca7..c9eb2e2f5559 100644
--- a/arch/x86/include/uapi/asm/kvm.h
+++ b/arch/x86/include/uapi/asm/kvm.h
@@ -952,8 +952,6 @@ struct kvm_tdx_cmd {
__u64 hw_error;
};
-#define KVM_TDX_CPUID_NO_SUBLEAF ((__u32)-1)
-
struct kvm_tdx_cpuid_config {
__u32 leaf;
__u32 sub_leaf;
diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c
index 90b44ebaf864..d89973e554f6 100644
--- a/arch/x86/kvm/vmx/tdx.c
+++ b/arch/x86/kvm/vmx/tdx.c
@@ -31,6 +31,19 @@ static void __used tdx_guest_keyid_free(int keyid)
ida_free(&tdx_guest_keyid_pool, keyid);
}
+#define KVM_TDX_CPUID_NO_SUBLEAF ((__u32)-1)
+
+struct kvm_tdx_caps {
+ u64 supported_attrs;
+ u64 supported_xfam;
+
+ u16 num_cpuid_config;
+ /* This must the last member. */
+ DECLARE_FLEX_ARRAY(struct kvm_tdx_cpuid_config, cpuid_configs);
+};
+
+static struct kvm_tdx_caps *kvm_tdx_caps;
+
static int tdx_get_capabilities(struct kvm_tdx_cmd *cmd)
{
const struct tdx_sysinfo_td_conf *td_conf =
&tdx_sysinfo->td_conf;
@@ -131,6 +144,68 @@ int tdx_vm_ioctl(struct kvm *kvm, void __user
*argp)
return r;
}
+#define KVM_SUPPORTED_TD_ATTRS (TDX_TD_ATTR_SEPT_VE_DISABLE)
Why isn't TDX_TD_ATTR_DEBUG added as well?
Because so far KVM doesn't support all the features of a DEBUG TD for
userspace. e.g., KVM doesn't provide interface for userspace to
read/write private memory of DEBUG TD.
But this means that you can't really run a TDX with SEPT_VE_DISABLE
disabled for debugging purposes, so perhaps it might be necessary to
rethink the condition allowing SEPT_VE_DISABLE to be disabled. Without
the debug flag and SEPT_VE_DISABLE disabled the code refuses to start
the VM, what if one wants to debug some SEPT issue by having an oops
generated inside the vm ?
sept_ve_disable is allowed to be disable, i.e., set to 0.
I think there must be some misunderstanding.
<snip>