On 1/22/24 10:28 AM, H. Peter Anvin wrote:
On January 22, 2024 8:32:22 AM PST, Dave Hansen <dave.hansen@xxxxxxxxx> wrote:
On 1/9/24 00:40, Alexey Makhalov wrote:
+#ifdef CONFIG_INTEL_TDX_GUEST
+unsigned long vmware_tdx_hypercall(unsigned long cmd,
+ struct tdx_module_args *args)
+{
+ if (!hypervisor_is_type(X86_HYPER_VMWARE))
+ return ULONG_MAX;
+
+ if (cmd & ~VMWARE_CMD_MASK) {
+ pr_warn_once("Out of range command %lx\n", cmd);
+ return ULONG_MAX;
+ }
+
+ args->r10 = VMWARE_TDX_VENDOR_LEAF;
+ args->r11 = VMWARE_TDX_HCALL_FUNC;
+ args->r12 = VMWARE_HYPERVISOR_MAGIC;
+ args->r13 = cmd;
+ args->r15 = 0; /* CPL */
+
+ __tdx_hypercall(args);
+
+ return args->r12;
+}
+EXPORT_SYMBOL_GPL(vmware_tdx_hypercall);
+#endif
This is the kind of wrapper that I was hoping for. Thanks.
Acked-by: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
I'm slightly confused by this TBH.
Why are the arguments passed in as a structure, which is modified by the wrapper to boot? This is analogous to a system call interface.
Furthermore, this is an out-of-line function; it should never be called with !X86_HYPER_VMWARE or you are introducing overhead for other hypervisors; I believe a pr_warn_once() is in order at least, just as you have for the out-of-range test.
This patch series introduces vmware_hypercall family of functions
similar to kvm_hypercall. Similarity: both vmware and kvm
implementations are static inline functions and both of them use
__tdx_hypercall (global not exported symbol). Difference: kvm_hypercall
functions are used _only_ within the kernel, but vmware_hypercall are
also used by modules.
Exporting __tdx_hypercall function is an original Dave's concern.
So we ended up with exporting wrapper, not generic, but VMware specific
with added checks against arbitrary use.
vmware_tdx_hypercall is not designed for !X86_HYPER_VMWARE callers. But
such a calls are not forbidden.
Arguments in a structure is an API for __tdx_hypercall(). Input and
output argument handling are done by vmware_hypercall callers, while
VMware specific dress up is inside the wrapper.
Peter, do you think code comments are required to make it clear for the
reader?
