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Message-ID: <bd61e29d-5842-4136-b30f-929b00bdf6f9@intel.com>
Date: Wed, 13 Mar 2024 11:44:08 +0800
From: Xiaoyao Li <xiaoyao.li@...el.com>
To: Kai Huang <kai.huang@...el.com>, linux-kernel@...r.kernel.org,
kvm@...r.kernel.org
Cc: x86@...nel.org, dave.hansen@...el.com, kirill.shutemov@...ux.intel.com,
peterz@...radead.org, tglx@...utronix.de, bp@...en8.de, mingo@...hat.com,
hpa@...or.com, seanjc@...gle.com, pbonzini@...hat.com,
isaku.yamahata@...el.com, jgross@...e.com
Subject: Re: [PATCH 5/5] x86/virt/tdx: Export global metadata read
infrastructure
On 3/1/2024 7:20 PM, Kai Huang wrote:
> KVM will need to read a bunch of non-TDMR related metadata to create and
> run TDX guests. Export the metadata read infrastructure for KVM to use.
>
> Specifically, export two helpers:
>
> 1) The helper which reads multiple metadata fields to a buffer of a
> structure based on the "field ID -> structure member" mapping table.
>
> 2) The low level helper which just reads a given field ID.
How about introducing a helper to read a single metadata field comparing
to 1) instead of the low level helper.
The low level helper tdx_sys_metadata_field_read() requires the data buf
to be u64 *. So the caller needs to use a temporary variable and handle
the memcpy when the field is less than 8 bytes.
so why not expose a high level helper to read single field, e.g.,
+int tdx_sys_metadata_read_single(u64 field_id, int bytes, void *buf)
+{
+ return stbuf_read_sys_metadata_field(field_id, 0, bytes, buf);
+}
+EXPORT_SYMBOL_GPL(tdx_sys_metadata_read_single);
> The two helpers cover cases when the user wants to cache a bunch of
> metadata fields to a certain structure and when the user just wants to
> query a specific metadata field on demand. They are enough for KVM to
> use (and also should be enough for other potential users).
>
> Signed-off-by: Kai Huang <kai.huang@...el.com>
> Reviewed-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
> ---
> arch/x86/include/asm/tdx.h | 22 ++++++++++++++++++++++
> arch/x86/virt/vmx/tdx/tdx.c | 25 ++++++++-----------------
> 2 files changed, 30 insertions(+), 17 deletions(-)
>
> diff --git a/arch/x86/include/asm/tdx.h b/arch/x86/include/asm/tdx.h
> index eba178996d84..709b9483f9e4 100644
> --- a/arch/x86/include/asm/tdx.h
> +++ b/arch/x86/include/asm/tdx.h
> @@ -116,6 +116,28 @@ static inline u64 sc_retry(sc_func_t func, u64 fn,
> int tdx_cpu_enable(void);
> int tdx_enable(void);
> const char *tdx_dump_mce_info(struct mce *m);
> +
> +struct tdx_metadata_field_mapping {
> + u64 field_id;
> + int offset;
> + int size;
> +};
> +
> +#define TD_SYSINFO_MAP(_field_id, _struct, _member) \
> + { .field_id = MD_FIELD_ID_##_field_id, \
> + .offset = offsetof(_struct, _member), \
> + .size = sizeof(typeof(((_struct *)0)->_member)) }
> +
> +/*
> + * Read multiple global metadata fields to a buffer of a structure
> + * based on the "field ID -> structure member" mapping table.
> + */
> +int tdx_sys_metadata_read(const struct tdx_metadata_field_mapping *fields,
> + int nr_fields, void *stbuf);
> +
> +/* Read a single global metadata field */
> +int tdx_sys_metadata_field_read(u64 field_id, u64 *data);
> +
> #else
> static inline void tdx_init(void) { }
> static inline int tdx_cpu_enable(void) { return -ENODEV; }
> diff --git a/arch/x86/virt/vmx/tdx/tdx.c b/arch/x86/virt/vmx/tdx/tdx.c
> index 4ee4b8cf377c..dc21310776ab 100644
> --- a/arch/x86/virt/vmx/tdx/tdx.c
> +++ b/arch/x86/virt/vmx/tdx/tdx.c
> @@ -251,7 +251,7 @@ static int build_tdx_memlist(struct list_head *tmb_list)
> return ret;
> }
>
> -static int read_sys_metadata_field(u64 field_id, u64 *data)
> +int tdx_sys_metadata_field_read(u64 field_id, u64 *data)
> {
> struct tdx_module_args args = {};
> int ret;
> @@ -270,6 +270,7 @@ static int read_sys_metadata_field(u64 field_id, u64 *data)
>
> return 0;
> }
> +EXPORT_SYMBOL_GPL(tdx_sys_metadata_field_read);
>
> /* Return the metadata field element size in bytes */
> static int get_metadata_field_bytes(u64 field_id)
> @@ -295,7 +296,7 @@ static int stbuf_read_sys_metadata_field(u64 field_id,
> if (WARN_ON_ONCE(get_metadata_field_bytes(field_id) != bytes))
> return -EINVAL;
>
> - ret = read_sys_metadata_field(field_id, &tmp);
> + ret = tdx_sys_metadata_field_read(field_id, &tmp);
> if (ret)
> return ret;
>
> @@ -304,19 +305,8 @@ static int stbuf_read_sys_metadata_field(u64 field_id,
> return 0;
> }
>
> -struct field_mapping {
> - u64 field_id;
> - int offset;
> - int size;
> -};
> -
> -#define TD_SYSINFO_MAP(_field_id, _struct, _member) \
> - { .field_id = MD_FIELD_ID_##_field_id, \
> - .offset = offsetof(_struct, _member), \
> - .size = sizeof(typeof(((_struct *)0)->_member)) }
> -
> -static int read_sys_metadata(const struct field_mapping *fields, int nr_fields,
> - void *stbuf)
> +int tdx_sys_metadata_read(const struct tdx_metadata_field_mapping *fields,
> + int nr_fields, void *stbuf)
> {
> int i, ret;
>
> @@ -331,6 +321,7 @@ static int read_sys_metadata(const struct field_mapping *fields, int nr_fields,
>
> return 0;
> }
> +EXPORT_SYMBOL_GPL(tdx_sys_metadata_read);
>
> #define TD_SYSINFO_MAP_TDMR_INFO(_field_id, _member) \
> TD_SYSINFO_MAP(_field_id, struct tdx_tdmr_sysinfo, _member)
> @@ -338,7 +329,7 @@ static int read_sys_metadata(const struct field_mapping *fields, int nr_fields,
> static int get_tdx_tdmr_sysinfo(struct tdx_tdmr_sysinfo *tdmr_sysinfo)
> {
> /* Map TD_SYSINFO fields into 'struct tdx_tdmr_sysinfo': */
> - const struct field_mapping fields[] = {
> + const struct tdx_metadata_field_mapping fields[] = {
> TD_SYSINFO_MAP_TDMR_INFO(MAX_TDMRS, max_tdmrs),
> TD_SYSINFO_MAP_TDMR_INFO(MAX_RESERVED_PER_TDMR, max_reserved_per_tdmr),
> TD_SYSINFO_MAP_TDMR_INFO(PAMT_4K_ENTRY_SIZE, pamt_entry_size[TDX_PS_4K]),
> @@ -347,7 +338,7 @@ static int get_tdx_tdmr_sysinfo(struct tdx_tdmr_sysinfo *tdmr_sysinfo)
> };
>
> /* Populate 'tdmr_sysinfo' fields using the mapping structure above: */
> - return read_sys_metadata(fields, ARRAY_SIZE(fields), tdmr_sysinfo);
> + return tdx_sys_metadata_read(fields, ARRAY_SIZE(fields), tdmr_sysinfo);
> }
>
> /* Calculate the actual TDMR size */
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