On 11/7/2023 10:55 PM, isaku.yamahata@xxxxxxxxx wrote:
> From: Isaku Yamahata <isaku.yamahata@xxxxxxxxx>
>
> Add helper functions to allocate/free TDX private host key id (HKID), and
> export the global TDX HKID.
>
> The memory controller encrypts TDX memory with the assigned TDX HKIDs. The
> global TDX HKID is to encrypt the TDX module, its memory, and some dynamic
> data (TDR). The private TDX HKID is assigned to guest TD to encrypt guest
> memory and the related data. When VMM releases an encrypted page for
> reuse, the page needs a cache flush with the used HKID. VMM needs the
> global TDX HKID and the private TDX HKIDs to flush encrypted pages.
>
> Signed-off-by: Isaku Yamahata <isaku.yamahata@xxxxxxxxx>
> ---
> arch/x86/include/asm/tdx.h | 12 ++++++++++++
> arch/x86/virt/vmx/tdx/tdx.c | 28 +++++++++++++++++++++++++++-
> 2 files changed, 39 insertions(+), 1 deletion(-)
>
> diff --git a/arch/x86/include/asm/tdx.h b/arch/x86/include/asm/tdx.h
> index b7cfdf084860..3b648f290af3 100644
> --- a/arch/x86/include/asm/tdx.h
> +++ b/arch/x86/include/asm/tdx.h
> @@ -114,6 +114,16 @@ int tdx_cpu_enable(void);
> int tdx_enable(void);
> void tdx_reset_memory(void);
> bool tdx_is_private_mem(unsigned long phys);
> +
> +/*
> + * Key id globally used by TDX module: TDX module maps TDR with this TDX global
> + * key id. TDR includes key id assigned to the TD. Then TDX module maps other
> + * TD-related pages with the assigned key id. TDR requires this TDX global key
> + * id for cache flush unlike other TD-related pages.
> + */
> +extern u32 tdx_global_keyid;
> +int tdx_guest_keyid_alloc(void);
> +void tdx_guest_keyid_free(int keyid);
> #else
> static inline u64 __seamcall(u64 fn, struct tdx_module_args *args)
> {
> @@ -132,6 +142,8 @@ static inline int tdx_cpu_enable(void) { return -ENODEV; }
> static inline int tdx_enable(void) { return -ENODEV; }
> static inline void tdx_reset_memory(void) { }
> static inline bool tdx_is_private_mem(unsigned long phys) { return false; }
> +static inline int tdx_guest_keyid_alloc(void) { return -EOPNOTSUPP; }
> +static inline void tdx_guest_keyid_free(int keyid) { }
> #endif /* CONFIG_INTEL_TDX_HOST */
>
> #endif /* !__ASSEMBLY__ */
> diff --git a/arch/x86/virt/vmx/tdx/tdx.c b/arch/x86/virt/vmx/tdx/tdx.c
> index 38ec6815a42a..c01cbfc81fbb 100644
> --- a/arch/x86/virt/vmx/tdx/tdx.c
> +++ b/arch/x86/virt/vmx/tdx/tdx.c
> @@ -37,7 +37,8 @@
> #include <asm/tdx.h>
> #include "tdx.h"
>
> -static u32 tdx_global_keyid __ro_after_init;
> +u32 tdx_global_keyid __ro_after_init;
> +EXPORT_SYMBOL_GPL(tdx_global_keyid);
> static u32 tdx_guest_keyid_start __ro_after_init;
> static u32 tdx_nr_guest_keyids __ro_after_init;
>
> @@ -105,6 +106,31 @@ static inline int sc_retry_prerr(sc_func_t func, sc_err_func_t err_func,
> #define seamcall_prerr_ret(__fn, __args) \
> sc_retry_prerr(__seamcall_ret, seamcall_err_ret, (__fn), (__args))
>
> +/* TDX KeyID pool */
> +static DEFINE_IDA(tdx_guest_keyid_pool);
> +
> +int tdx_guest_keyid_alloc(void)
> +{
> + if (WARN_ON_ONCE(!tdx_guest_keyid_start || !tdx_nr_guest_keyids))
> + return -EINVAL;
> +
> + /* The first keyID is reserved for the global key. */
> + return ida_alloc_range(&tdx_guest_keyid_pool, tdx_guest_keyid_start + 1,
Per
https://lore.kernel.org/all/121aab11b48b4e6550cfe6d23b4daab744ee2076.1697532085.git.kai.huang@xxxxxxxxx/
tdx_guest_keyid_start has already reserved the first keyID for global
key, I think we don't need to reserve another one here.
> + tdx_guest_keyid_start + tdx_nr_guest_keyids - 1,
> + GFP_KERNEL);
> +}
> +EXPORT_SYMBOL_GPL(tdx_guest_keyid_alloc);
> +
> +void tdx_guest_keyid_free(int keyid)
> +{
> + /* keyid = 0 is reserved. */
> + if (WARN_ON_ONCE(keyid <= 0))
> + return;
> +
> + ida_free(&tdx_guest_keyid_pool, keyid);
> +}
> +EXPORT_SYMBOL_GPL(tdx_guest_keyid_free);
> +
> /*
> * Do the module global initialization once and return its result.
> * It can be done on any cpu. It's always called with interrupts
