linux-kernel - Re: [PATCH v2] virt: tdx-guest: Add Quote generation support using TSM

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Date:   Wed, 20 Sep 2023 20:52:48 +0300
From:   "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>
To:     Kuppuswamy Sathyanarayanan 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Dan Williams <dan.j.williams@...el.com>,
        "H . Peter Anvin" <hpa@...or.com>, Tony Luck <tony.luck@...el.com>,
        Wander Lairson Costa <wander@...hat.com>,
        Erdem Aktas <erdemaktas@...gle.com>,
        Dionna Amalie Glaze <dionnaglaze@...gle.com>,
        Qinkun Bao <qinkun@...che.org>,
        Guorui Yu <GuoRui.Yu@...ux.alibaba.com>,
        linux-coco@...ts.linux.dev, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] virt: tdx-guest: Add Quote generation support using
 TSM_REPORTS

On Wed, Sep 20, 2023 at 08:27:39AM -0700, Kuppuswamy Sathyanarayanan wrote:
> 
> 
> On 9/20/2023 6:16 AM, Kirill A . Shutemov wrote:
> >> +static u8 *tdx_report_new(const struct tsm_desc *desc, void *data, size_t *outblob_len)
> >> +{
> >> +	struct tdx_quote_buf *quote_buf = quote_data;
> >> +	int ret;
> >> +	u8 *buf;
> >> +	u64 err;
> >> +
> >> +	if (mutex_lock_interruptible(&quote_lock))
> >> +		return ERR_PTR(-EINTR);
> >> +
> >> +	/*
> >> +	 * If the previous request is timedout or interrupted, and the
> >> +	 * Quote buf status is still in GET_QUOTE_IN_FLIGHT (owned by
> >> +	 * VMM), don't permit any new request.
> >> +	 */
> >> +	if (quote_buf->status == GET_QUOTE_IN_FLIGHT) {
> >> +		ret = -EBUSY;
> >> +		goto done;
> >> +	}
> >> +
> >> +	if (desc->inblob_len != TDX_REPORTDATA_LEN) {
> >> +		ret = -EINVAL;
> >> +		goto done;
> >> +	}
> >> +
> >> +	/* TDX attestation only supports default format request */
> >> +	if (desc->outblob_format != TSM_FORMAT_DEFAULT) {
> >> +		ret = -EINVAL;
> >> +		goto done;
> >> +	}
> >> +
> >> +	u8 *reportdata __free(kfree) = kmalloc(TDX_REPORTDATA_LEN, GFP_KERNEL);
> > __free() is new to me. Good to know.
> > 
> > But are we okay now with declaring variables in the middle of the
> > function? Any reason we can't do at the top?
> 
> Declaring variables at the top is no longer a hard requirement. The main reason
> for declaring it here is to use __free cleanup function. If we use top
> declaration, then we have free it manually.

What's wrong with allocating it it there too?

-- 
  Kiryl Shutsemau / Kirill A. Shutemov