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Date:   Tue, 8 Feb 2022 13:12:45 +0100
From:   Borislav Petkov <bp@alien8.de>
To:     "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc:     tglx@linutronix.de, mingo@redhat.com, dave.hansen@intel.com,
        luto@kernel.org, peterz@infradead.org,
        sathyanarayanan.kuppuswamy@linux.intel.com, aarcange@redhat.com,
        ak@linux.intel.com, dan.j.williams@intel.com, david@redhat.com,
        hpa@zytor.com, jgross@suse.com, jmattson@google.com,
        joro@8bytes.org, jpoimboe@redhat.com, knsathya@kernel.org,
        pbonzini@redhat.com, sdeep@vmware.com, seanjc@google.com,
        tony.luck@intel.com, vkuznets@redhat.com, wanpengli@tencent.com,
        x86@kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCHv2 23/29] x86/tdx: Add helper to convert memory between
 shared and private
Message-ID: <YgJePUqMEzHNqrsR@zn.tnic>
References: <20220124150215.36893-1-kirill.shutemov@linux.intel.com>
 <20220124150215.36893-24-kirill.shutemov@linux.intel.com>
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In-Reply-To: <20220124150215.36893-24-kirill.shutemov@linux.intel.com>
Precedence: bulk

On Mon, Jan 24, 2022 at 06:02:09PM +0300, Kirill A. Shutemov wrote:
> +static bool tdx_accept_page(phys_addr_t gpa, enum pg_level pg_level)

accept_page() as it is a static function.

> +int tdx_hcall_request_gpa_type(phys_addr_t start, phys_addr_t end, bool enc)
> +{
> +	u64 ret;
> +
> +	if (end <= start)
> +		return -EINVAL;
> +
> +	if (!enc) {
> +		start |= tdx_shared_mask();
> +		end |= tdx_shared_mask();
> +	}
> +
> +	/*
> +	 * Notify the VMM about page mapping conversion. More info about ABI
> +	 * can be found in TDX Guest-Host-Communication Interface (GHCI),
> +	 * sec "TDG.VP.VMCALL<MapGPA>"
> +	 */
> +	ret = _tdx_hypercall(TDVMCALL_MAP_GPA, start, end - start, 0, 0, NULL);
> +


^ Superfluous newline.

> +	if (ret)
> +		ret = -EIO;
> +
> +	if (ret || !enc)

Is the second case here after the "||" the conversion-to-shared where it
only needs to notify with MapGPA and return?

Of all the places, this one needs a comment.

> +		return ret;
> +
> +	/*
> +	 * For shared->private conversion, accept the page using
> +	 * TDX_ACCEPT_PAGE TDX module call.
> +	 */
> +	while (start < end) {
> +		/* Try 2M page accept first if possible */
> +		if (!(start & ~PMD_MASK) && end - start >= PMD_SIZE &&
> +		    !tdx_accept_page(start, PG_LEVEL_2M)) {

What happens here if the module doesn't accept the page? No error
reporting, no error handling, no warning, nada?

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette