Re: [PATCH v4 1/3] x86/tdx: Add TDX Guest attestation interface driver
From: Dave Hansen
Date: Thu Apr 28 2022 - 14:04:56 EST
On 4/28/22 10:56, Sathyanarayanan Kuppuswamy wrote:
> On 4/28/22 10:45 AM, Wander Lairson Costa wrote:
>> On Fri, Apr 22, 2022 at 04:34:16PM -0700, Kuppuswamy Sathyanarayanan
>>> +static long tdx_get_tdreport(void __user *argp)
>>> + void *report_buf = NULL, *tdreport_buf = NULL;
>>> + long ret = 0, err;
>>> + /* Allocate space for report data */
>>> + report_buf = kmalloc(TDX_REPORT_DATA_LEN, GFP_KERNEL);
>>> + if (!report_buf)
>>> + return -ENOMEM;
>>> + /*
>>> + * Allocate space for TDREPORT buffer (1024-byte aligned).
>>> + * Full page alignment is more than enough.
>>> + */
>>> + tdreport_buf = (void *)get_zeroed_page(GFP_KERNEL);
>> Maybe we should add BUILD_BUG_ON(TDX_TDREPORT_LEN > PAGE_SIZE)
> Currently, it is a constant value < PAGE_SIZE. But I can add the
> BUILD_BUG_ON check for it.
That's kinda silly. If it might ever be bigger than a page, you just do:
tdreport_buf = alloc_pages();
But, seriously, TDX_TDREPORT_LEN is part of the ABI and can't change.
kmalloc() would work too since TDX_TDREPORT_LEN is a power of 2.