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SubjectRe: [PATCH v11 013/113] x86/cpu: Add helper functions to allocate/free TDX private host key id
On Thu, 12 Jan 2023 08:31:21 -0800
isaku.yamahata@intel.com wrote:

> From: Isaku Yamahata <isaku.yamahata@intel.com>
>
> TDX private host key id (HKID) is assigned to guest TD. The memory
> controller encrypts guest TD memory with the assigned TDX HKID. Add
> helper functions to allocate/free TDX private HKID so that TDX KVM can
> manage it.
>
> Also export the global TDX private HKID that is used to encrypt TDX
> module, its memory and some dynamic data (TDR). When VMM releasing
> encrypted page to reuse it, the page needs to be flushed with the used
> HKID. VMM needs the global TDX private HKID to flush such pages.
>
> Signed-off-by: Isaku Yamahata <isaku.yamahata@intel.com>
> ---
> arch/x86/include/asm/tdx.h | 12 ++++++++++++
> arch/x86/virt/vmx/tdx/tdx.c | 35 +++++++++++++++++++++++++++++++++++
> 2 files changed, 47 insertions(+)
>
> diff --git a/arch/x86/include/asm/tdx.h b/arch/x86/include/asm/tdx.h
> index 0f71d3856ede..ed9cf61ff8b4 100644
> --- a/arch/x86/include/asm/tdx.h
> +++ b/arch/x86/include/asm/tdx.h
> @@ -107,11 +107,23 @@ static inline long tdx_kvm_hypercall(unsigned int
> nr, unsigned long p1, #ifdef CONFIG_INTEL_TDX_HOST
> bool platform_tdx_enabled(void);
> int tdx_enable(void);
> +/*
> + * 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 __read_mostly;
> +int tdx_keyid_alloc(void);
> +void tdx_keyid_free(int keyid);
> +
> u64 __seamcall(u64 op, u64 rcx, u64 rdx, u64 r8, u64 r9,
> struct tdx_module_output *out);
> #else /* !CONFIG_INTEL_TDX_HOST */
> static inline bool platform_tdx_enabled(void) { return false; }
> static inline int tdx_enable(void) { return -EINVAL; }
> +static inline int tdx_keyid_alloc(void) { return -EOPNOTSUPP; }
> +static inline void tdx_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 eba7e62cebec..d18ab5c4d447 100644
> --- a/arch/x86/virt/vmx/tdx/tdx.c
> +++ b/arch/x86/virt/vmx/tdx/tdx.c
> @@ -51,6 +51,10 @@ static DEFINE_MUTEX(tdx_module_lock);
> /* All TDX-usable memory regions */
> static LIST_HEAD(tdx_memlist);
>
> +/* TDX module global KeyID. Used in TDH.SYS.CONFIG ABI. */
> +u32 tdx_global_keyid __read_mostly;
> +EXPORT_SYMBOL_GPL(tdx_global_keyid);
> +
> /*
> * tdx_keyid_start and nr_tdx_keyids indicate that TDX is uninitialized.
> * This is used in TDX initialization error paths to take it from
> @@ -132,6 +136,31 @@ static struct notifier_block tdx_memory_nb = {
> .notifier_call = tdx_memory_notifier,
> };
>
> +/* TDX KeyID pool */
> +static DEFINE_IDA(tdx_keyid_pool);
> +
> +int tdx_keyid_alloc(void)
> +{
> + if (WARN_ON_ONCE(!tdx_keyid_start || !nr_tdx_keyids))
> + return -EINVAL;

Better mention that tdx_keyid_start and nr_tdx_keyids are defined in
another patches.

> +
> + /* The first keyID is reserved for the global key. */
> + return ida_alloc_range(&tdx_keyid_pool, tdx_keyid_start + 1,
> + tdx_keyid_start + nr_tdx_keyids - 1,
> + GFP_KERNEL);
> +}
> +EXPORT_SYMBOL_GPL(tdx_keyid_alloc);
> +
> +void tdx_keyid_free(int keyid)
> +{
> + /* keyid = 0 is reserved. */
> + if (WARN_ON_ONCE(keyid <= 0))
> + return;
> +
> + ida_free(&tdx_keyid_pool, keyid);
> +}
> +EXPORT_SYMBOL_GPL(tdx_keyid_free);
> +
> static int __init tdx_init(void)
> {
> int err;
> @@ -1161,6 +1190,12 @@ static int init_tdx_module(void)
> if (ret)
> goto out_free_pamts;
>
> + /*
> + * Reserve the first TDX KeyID as global KeyID to protect
> + * TDX module metadata.
> + */
> + tdx_global_keyid = tdx_keyid_start;
> +
> /* Initialize TDMRs to complete the TDX module initialization */
> ret = init_tdmrs(&tdmr_list);
> if (ret)

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