On Sun, 12 Mar 2023 10:55:38 -0700
isaku.yamahata@xxxxxxxxx wrote:
> From: Isaku Yamahata <isaku.yamahata@xxxxxxxxx>
>
> 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.
>
^ This sentence should go to the below paragraph, which is "problem/way to go"
paragraph. For "background" paragraph, you can talk more about the usage of
HKID, like global/private HKID. Then you don't need to introduce them again in
the below paragraph and just talk about the solution.
> 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@xxxxxxxxx>
> ---
> arch/x86/include/asm/tdx.h | 12 ++++++++++++
> arch/x86/virt/vmx/tdx/tdx.c | 34 +++++++++++++++++++++++++++++++++-
> 2 files changed, 45 insertions(+), 1 deletion(-)
>
> diff --git a/arch/x86/include/asm/tdx.h b/arch/x86/include/asm/tdx.h
> index 6c01ab572c1f..7d99a48a98cc 100644
> --- a/arch/x86/include/asm/tdx.h
> +++ b/arch/x86/include/asm/tdx.h
> @@ -104,6 +104,16 @@ static inline long tdx_kvm_hypercall(unsigned int nr, unsigned long p1,
> bool platform_tdx_enabled(void);
> int tdx_cpu_enable(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 __ro_after_init;
> +int tdx_guest_keyid_alloc(void);
> +void tdx_guest_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 */
> @@ -112,6 +122,8 @@ static inline int tdx_cpu_enable(void) { return -EINVAL; }
> static inline int tdx_enable(void) { return -EINVAL; }
> static inline u64 __seamcall(u64 op, u64 rcx, u64 rdx, u64 r8, u64 r9,
> struct tdx_module_output *out) { return TDX_SEAMCALL_UD; };
> +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 ee94a7327d93..3251fdf74667 100644
> --- a/arch/x86/virt/vmx/tdx/tdx.c
> +++ b/arch/x86/virt/vmx/tdx/tdx.c
> @@ -33,7 +33,8 @@
> #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;
>
> @@ -138,6 +139,31 @@ static struct notifier_block tdx_memory_nb = {
> .notifier_call = tdx_memory_notifier,
> };
>
> +/* 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,
> + 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);
> +
> static int __init tdx_init(void)
> {
> u32 tdx_keyid_start, nr_tdx_keyids;
> @@ -1218,6 +1244,12 @@ 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);
>
