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Message-ID: <8972b2ac-c786-8ff5-74fc-040cd4d81c86@linux.intel.com>
Date: Sun, 24 Apr 2022 19:58:06 -0700
From: Sathyanarayanan Kuppuswamy
<sathyanarayanan.kuppuswamy@...ux.intel.com>
To: Kai Huang <kai.huang@...el.com>, linux-kernel@...r.kernel.org,
kvm@...r.kernel.org
Cc: seanjc@...gle.com, pbonzini@...hat.com, dave.hansen@...el.com,
len.brown@...el.com, tony.luck@...el.com,
rafael.j.wysocki@...el.com, reinette.chatre@...el.com,
dan.j.williams@...el.com, peterz@...radead.org, ak@...ux.intel.com,
kirill.shutemov@...ux.intel.com, isaku.yamahata@...el.com
Subject: Re: [PATCH v3 09/21] x86/virt/tdx: Get information about TDX module
and convertible memory
On 4/5/22 9:49 PM, Kai Huang wrote:
> TDX provides increased levels of memory confidentiality and integrity.
> This requires special hardware support for features like memory
> encryption and storage of memory integrity checksums. Not all memory
> satisfies these requirements.
>
> As a result, TDX introduced the concept of a "Convertible Memory Region"
> (CMR). During boot, the firmware builds a list of all of the memory
> ranges which can provide the TDX security guarantees. The list of these
> ranges, along with TDX module information, is available to the kernel by
> querying the TDX module via TDH.SYS.INFO SEAMCALL.
>
> Host kernel can choose whether or not to use all convertible memory
> regions as TDX memory. Before TDX module is ready to create any TD
> guests, all TDX memory regions that host kernel intends to use must be
> configured to the TDX module, using specific data structures defined by
> TDX architecture. Constructing those structures requires information of
> both TDX module and the Convertible Memory Regions. Call TDH.SYS.INFO
> to get this information as preparation to construct those structures.
>
> Signed-off-by: Kai Huang <kai.huang@...el.com>
> ---
Looks good. Some minor comments.
> arch/x86/virt/vmx/tdx/tdx.c | 131 ++++++++++++++++++++++++++++++++++++
> arch/x86/virt/vmx/tdx/tdx.h | 61 +++++++++++++++++
> 2 files changed, 192 insertions(+)
>
> diff --git a/arch/x86/virt/vmx/tdx/tdx.c b/arch/x86/virt/vmx/tdx/tdx.c
> index ef2718423f0f..482e6d858181 100644
> --- a/arch/x86/virt/vmx/tdx/tdx.c
> +++ b/arch/x86/virt/vmx/tdx/tdx.c
> @@ -80,6 +80,11 @@ static DEFINE_MUTEX(tdx_module_lock);
>
> static struct p_seamldr_info p_seamldr_info;
>
> +/* Base address of CMR array needs to be 512 bytes aligned. */
> +static struct cmr_info tdx_cmr_array[MAX_CMRS] __aligned(CMR_INFO_ARRAY_ALIGNMENT);
> +static int tdx_cmr_num;
> +static struct tdsysinfo_struct tdx_sysinfo;
> +
> static bool __seamrr_enabled(void)
> {
> return (seamrr_mask & SEAMRR_ENABLED_BITS) == SEAMRR_ENABLED_BITS;
> @@ -468,6 +473,127 @@ static int tdx_module_init_cpus(void)
> return seamcall_on_each_cpu(&sc);
> }
>
> +static inline bool cmr_valid(struct cmr_info *cmr)
> +{
> + return !!cmr->size;
> +}
> +
> +static void print_cmrs(struct cmr_info *cmr_array, int cmr_num,
> + const char *name)
> +{
> + int i;
> +
> + for (i = 0; i < cmr_num; i++) {
> + struct cmr_info *cmr = &cmr_array[i];
> +
> + pr_info("%s : [0x%llx, 0x%llx)\n", name,
> + cmr->base, cmr->base + cmr->size);
> + }
I am not sure if it is ok to print this info by default or pr_debug
would be better. I will let maintainers decide about it.
> +}
> +
> +static int sanitize_cmrs(struct cmr_info *cmr_array, int cmr_num)
Since this function only deals with tdx_cmr_array, why pass it
as argument?
> +{
> + int i, j;
> +
> + /*
> + * Intel TDX module spec, 20.7.3 CMR_INFO:
> + *
> + * TDH.SYS.INFO leaf function returns a MAX_CMRS (32) entry
> + * array of CMR_INFO entries. The CMRs are sorted from the
> + * lowest base address to the highest base address, and they
> + * are non-overlapping.
> + *
> + * This implies that BIOS may generate invalid empty entries
> + * if total CMRs are less than 32. Skip them manually.
> + */
> + for (i = 0; i < cmr_num; i++) {
> + struct cmr_info *cmr = &cmr_array[i];
> + struct cmr_info *prev_cmr = NULL;
Why not keep declarations together at the top of the function?
> +
> + /* Skip further invalid CMRs */
> + if (!cmr_valid(cmr))
> + break;
> +
> + if (i > 0)
> + prev_cmr = &cmr_array[i - 1];
> +
> + /*
> + * It is a TDX firmware bug if CMRs are not
> + * in address ascending order.
> + */
> + if (prev_cmr && ((prev_cmr->base + prev_cmr->size) >
> + cmr->base)) {
> + pr_err("Firmware bug: CMRs not in address ascending order.\n");
> + return -EFAULT;
> + }
Since above condition is only true for i > 0 case, why not combine them
together if (i > 0) {...}
> + }
> +
> + /*
> + * Also a sane BIOS should never generate invalid CMR(s) between
> + * two valid CMRs. Sanity check this and simply return error in
> + * this case.
> + *
> + * By reaching here @i is the index of the first invalid CMR (or
> + * cmr_num). Starting with next entry of @i since it has already
> + * been checked.
> + */
> + for (j = i + 1; j < cmr_num; j++)
> + if (cmr_valid(&cmr_array[j])) {
> + pr_err("Firmware bug: invalid CMR(s) among valid CMRs.\n");
> + return -EFAULT;
> + }
> +
> + /*
> + * Trim all tail invalid empty CMRs. BIOS should generate at
> + * least one valid CMR, otherwise it's a TDX firmware bug.
> + */
> + tdx_cmr_num = i;
> + if (!tdx_cmr_num) {
> + pr_err("Firmware bug: No valid CMR.\n");
> + return -EFAULT;
> + }
> +
> + /* Print kernel sanitized CMRs */
> + print_cmrs(tdx_cmr_array, tdx_cmr_num, "Kernel-sanitized-CMR");
> +
> + return 0;
> +}
> +
--
Sathyanarayanan Kuppuswamy
Linux Kernel Developer
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