Re: [PATCH v4 4/4] virt: tdx-guest: Allocate Quote buffer dynamically

[Peter Fang]

On Wed, Sep 16, 2026 at 01:31:07PM +0100, Kiryl Shutsemau wrote:
> On Tue, Sep 15, 2026 at 02:26:03AM -0700, Peter Fang wrote:
> > From: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@xxxxxxxxxxxxxxx>
> > 
> > A new TDX module ABI reports the Quote size limit in a metadata field.
> > Prior to this, the guest driver uses a fixed 128KB buffer. Intel derived
> > this number from current Quote types, but that is not sustainable as
> > Quotes evolve. 128KB may be too small for Quotes using schemes such as
> > post-quantum cryptography (PQC), where larger certificate chains can
> > increase the Quote size significantly. With this ABI, the guest no
> > longer has to rely on some empirical number.
> > 
> > Allocate the Quote buffer based on the reported limit. This avoids
> > wasting memory on platforms that do not need larger Quotes. Older
> > platforms fall back to the default 128KB buffer.
> > 
> > As a result, the maximum size of the "outblob" file in configfs-tsm now
> > depends on the TDX module.
> > 
> > Because the Quote buffer must be physically contiguous, its size is
> > bound by the buddy allocator's maximum page order (4MB), which should be
> > sufficient for current attestation needs.
> > 
> > Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@xxxxxxxxxxxxxxx>
> > Signed-off-by: Peter Fang <peter.fang@xxxxxxxxx>
> > Reviewed-by: Tony Lindgren <tony.lindgren@xxxxxxxxxxxxxxx>
> 
> Reviewed-by: Kiryl Shutsemau (Meta) <kas@xxxxxxxxxx>

Thanks a lot for coming back to this Kiryl!

> 
> -- 
>   Kiryl Shutsemau / Kirill A. Shutemov