On 1/23/2024 7:52 AM, isaku.yamahata@intel.com wrote:
> From: Isaku Yamahata <isaku.yamahata@intel.com>
>
> Some SEAMCALL may return TDX_RND_NO_ENTROPY error when the entropy is
> lacking. Retry SEAMCALL on the error following rdrand_long() to retry
> RDRAND_RETRY_LOOPS times.
>
> Signed-off-by: Isaku Yamahata <isaku.yamahata@intel.com>
> ---
> v18:
> - update to use struct tdx_modules_args for inputs.
> ---
> arch/x86/kvm/vmx/tdx_errno.h | 1 +
> arch/x86/kvm/vmx/tdx_ops.h | 15 +++++++++++----
> 2 files changed, 12 insertions(+), 4 deletions(-)
>
> diff --git a/arch/x86/kvm/vmx/tdx_errno.h b/arch/x86/kvm/vmx/tdx_errno.h
> index 7f96696b8e7c..bb093e292fef 100644
> --- a/arch/x86/kvm/vmx/tdx_errno.h
> +++ b/arch/x86/kvm/vmx/tdx_errno.h
> @@ -14,6 +14,7 @@
> #define TDX_OPERAND_INVALID 0xC000010000000000ULL
> #define TDX_OPERAND_BUSY 0x8000020000000000ULL
> #define TDX_PREVIOUS_TLB_EPOCH_BUSY 0x8000020100000000ULL
> +#define TDX_RND_NO_ENTROPY 0x8000020300000000ULL
> #define TDX_VCPU_NOT_ASSOCIATED 0x8000070200000000ULL
> #define TDX_KEY_GENERATION_FAILED 0x8000080000000000ULL
> #define TDX_KEY_STATE_INCORRECT 0xC000081100000000ULL
> diff --git a/arch/x86/kvm/vmx/tdx_ops.h b/arch/x86/kvm/vmx/tdx_ops.h
> index 0e26cf22240e..f4c16e5265f0 100644
> --- a/arch/x86/kvm/vmx/tdx_ops.h
> +++ b/arch/x86/kvm/vmx/tdx_ops.h
> @@ -6,6 +6,7 @@
>
> #include <linux/compiler.h>
>
> +#include <asm/archrandom.h>
> #include <asm/cacheflush.h>
> #include <asm/asm.h>
> #include <asm/kvm_host.h>
> @@ -17,14 +18,20 @@
> static inline u64 tdx_seamcall(u64 op, struct tdx_module_args *in,
> struct tdx_module_args *out)
> {
> + struct tdx_module_args args;
> + int retry;
> u64 ret;
>
> - if (out) {
> + if (!out)
> + out = &args;
> +
> + /* Mimic the existing rdrand_long() to retry RDRAND_RETRY_LOOPS times. */
> + retry = RDRAND_RETRY_LOOPS;
> + do {
> + /* As __seamcall_ret() overwrites out, init out on each loop. */
> *out = *in;
> ret = __seamcall_ret(op, out);
> - } else
> - ret = __seamcall(op, in);
> -
> + } while (unlikely(ret == TDX_RND_NO_ENTROPY) && --retry);
> if (unlikely(ret == TDX_SEAMCALL_UD)) {
> /*
> * SEAMCALLs fail with TDX_SEAMCALL_UD returned when VMX is off.
One question is when the return code is TDX_RND_NO_ENTROPY, does the input
tdx_module_args value will be modified or not?
As mentioned by Kai in previous review, there are seamcall*() variants which
handle TDX_RND_NO_ENTROPY already.
If the input tdx_module_args is not modified by a seamcall when the return
code is TDX_RND_NO_ENTROPY, the seamcall_ret() can be used directly.
But if the input tdx_module_args could be modified by a seamcall when the
return code is TDX_RND_NO_ENTROPY, the implementations of seamcall_ret() and
seamcall_saved_ret() have problem then, because the input tdx_module_args is
not re-initialized when retry.
They need to be fixed or deleted (no one is using them currently).