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    SubjectRe: [PATCH v8 019/103] x86/cpu: Add helper functions to allocate/free TDX private host key id
    On Sun, Aug 07, 2022 at 03:01:04PM -0700, isaku.yamahata@intel.com wrote:
    > From: Isaku Yamahata <isaku.yamahata@intel.com>
    >
    > TDX private host key id is assigned to guest TD. The memory controller
    > encrypts guest TD memory with the assigned TDX private host key id (HIKD).
    > Add helper functions to allocate/free TDX private host key id so that TDX
    > KVM manage it.
    >
    > Also export the global TDX private host key id 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 host
    > key id. VMM needs the global TDX private host key id to flush such pages
    > TDX module accesses with the global TDX private host key id.
    >
    > Signed-off-by: Isaku Yamahata <isaku.yamahata@intel.com>
    > ---
    > 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 c887618e3cec..a32e8881e758 100644
    > --- a/arch/x86/include/asm/tdx.h
    > +++ b/arch/x86/include/asm/tdx.h
    > @@ -144,6 +144,16 @@ struct tdsysinfo_struct {
    > bool platform_tdx_enabled(void);
    > int tdx_init(void);
    > const struct tdsysinfo_struct *tdx_get_sysinfo(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 */
    > @@ -151,6 +161,8 @@ static inline bool platform_tdx_enabled(void) { return false; }
    > static inline int tdx_init(void) { return -ENODEV; }
    > struct tdsysinfo_struct;
    > static inline const struct tdsysinfo_struct *tdx_get_sysinfo(void) { return NULL; }
    > +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 918e79159bbf..2168e6133d45 100644
    > --- a/arch/x86/virt/vmx/tdx/tdx.c
    > +++ b/arch/x86/virt/vmx/tdx/tdx.c
    > @@ -56,7 +56,8 @@ static struct cmr_info tdx_cmr_array[MAX_CMRS] __aligned(CMR_INFO_ARRAY_ALIGNMEN
    > static int tdx_cmr_num;
    >
    > /* TDX module global KeyID. Used in TDH.SYS.CONFIG ABI. */
    > -static u32 tdx_global_keyid;
    > +u32 tdx_global_keyid __read_mostly;
    > +EXPORT_SYMBOL_GPL(tdx_global_keyid);
    >
    > /* Detect whether CPU supports SEAM */
    > static int detect_seam(void)
    > @@ -80,6 +81,31 @@ static int detect_seam(void)
    > return 0;
    > }
    >
    > +/* TDX KeyID pool */
    > +static DEFINE_IDA(tdx_keyid_pool);
    > +
    > +int tdx_keyid_alloc(void)
    > +{
    > + if (WARN_ON_ONCE(!tdx_keyid_start || !tdx_keyid_num))
    > + return -EINVAL;
    > +
    > + /* The first keyID is reserved for the global key. */
    > + return ida_alloc_range(&tdx_keyid_pool, tdx_keyid_start + 1,
    > + tdx_keyid_start + tdx_keyid_num - 1,
    > + GFP_KERNEL);
    > +}
    > +EXPORT_SYMBOL_GPL(tdx_keyid_alloc);
    > +
    > +void tdx_keyid_free(int keyid)
    > +{
    > + /* keyid = 0 is reserved. */
    > + if (!keyid || keyid <= 0)

    keyid <=0 covers !keyid.

    > + return;
    > +
    > + ida_free(&tdx_keyid_pool, keyid);
    > +}
    > +EXPORT_SYMBOL_GPL(tdx_keyid_free);
    > +
    > static int detect_tdx_keyids(void)
    > {
    > u64 keyid_part;
    > --
    > 2.25.1
    >

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