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From: Jarkko Sakkinen <jarkko@kernel.org>
To: Jonathan McDowell <noodles@earth.li>
Cc: linux-integrity@vger.kernel.org,
	"David S . Miller" <davem@davemloft.net>,
	Herbert Xu <herbert@gondor.apana.org.au>,
	Eric Biggers <ebiggers@kernel.org>,
	Peter Huewe <peterhuewe@gmx.de>, Jason Gunthorpe <jgg@ziepe.ca>,
	David Howells <dhowells@redhat.com>,
	Paul Moore <paul@paul-moore.com>,
	James Morris <jmorris@namei.org>,
	"Serge E. Hallyn" <serge@hallyn.com>,
	open list <linux-kernel@vger.kernel.org>,
	"open list:KEYS/KEYRINGS" <keyrings@vger.kernel.org>,
	"open list:SECURITY SUBSYSTEM"
	<linux-security-module@vger.kernel.org>
Subject: Re: [PATCH v8 04/12] tpm: Change tpm_get_random() opportunistic
Date: Fri, 2 Jan 2026 18:37:43 +0200	[thread overview]
Message-ID: <aVf0V7GOtekOiSi7@kernel.org> (raw)
In-Reply-To: <aUUd760l89lrNOs-@earth.li>

On Fri, Dec 19, 2025 at 09:42:07AM +0000, Jonathan McDowell wrote:
> On Tue, Dec 16, 2025 at 11:21:38AM +0200, Jarkko Sakkinen wrote:
> > hwrng framework does not have a requirement that the all bytes requested
> > need to be provided. By enforcing such a requirement internally, TPM driver
> > can cause unpredictability in latency, as a single tpm_get_random() call
> > can result multiple TPM commands.
> > 
> > Especially, when TCG_TPM2_HMAC is enabled, extra roundtrips could have
> > significant effect to the system latency.
> > 
> > Thus, send TPM command only once and return bytes received instead of
> > committing to the number of requested bytes.
> 
> Function comment for tpm_get_random needs updated as well, as it currently
> says "until all of the @max bytes have been received", which is no longer
> true with this patch. With that:
> 
> Reviewed-by: Jonathan McDowell <noodles@meta.com>

Thank you and definitely can refine that comment. After holidays it is
probably to go through this patch set with time and send +1 iteration
:-)

BR, Jarkko

  reply	other threads:[~2026-01-02 16:37 UTC|newest]

Thread overview: 25+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2025-12-16  9:21 [PATCH v8 00/12] Streamline TPM2 HMAC sessions Jarkko Sakkinen
2025-12-16  9:21 ` [PATCH v8 01/12] KEYS: trusted: Use get_random-fallback for TPM Jarkko Sakkinen
2025-12-16  9:21 ` [PATCH v8 02/12] KEYS: trusted: Use get_random_bytes_wait() instead of tpm_get_random() Jarkko Sakkinen
2025-12-19  9:21   ` Jonathan McDowell
2026-01-02 16:34     ` Jarkko Sakkinen
2025-12-16  9:21 ` [PATCH v8 03/12] tpm: Orchestrate TPM commands in tpm_get_random() Jarkko Sakkinen
2025-12-19  9:43   ` Jonathan McDowell
2026-01-02 16:40     ` Jarkko Sakkinen
2025-12-16  9:21 ` [PATCH v8 04/12] tpm: Change tpm_get_random() opportunistic Jarkko Sakkinen
2025-12-16 22:03   ` Jarkko Sakkinen
2025-12-19  9:42   ` Jonathan McDowell
2026-01-02 16:37     ` Jarkko Sakkinen [this message]
2025-12-16  9:21 ` [PATCH v8 05/12] tpm2-sessions: Define TPM2_NAME_MAX_SIZE Jarkko Sakkinen
2025-12-19  9:32   ` Jonathan McDowell
2026-01-02 16:35     ` Jarkko Sakkinen
2025-12-16  9:21 ` [PATCH v8 06/12] KEYS: trusted: Open code tpm2_buf_append() Jarkko Sakkinen
2025-12-16  9:21 ` [PATCH v8 07/12] KEYS: trusted: Remove dead branch from tpm2_unseal_cmd Jarkko Sakkinen
2025-12-19  9:37   ` Jonathan McDowell
2025-12-19 20:54   ` James Bottomley
2026-01-02 16:31     ` Jarkko Sakkinen
2025-12-16  9:21 ` [PATCH v8 08/12] KEYS: trusted: Re-orchestrate tpm2_read_public() calls Jarkko Sakkinen
2025-12-16  9:21 ` [PATCH v8 09/12] tpm2-sessions: Remove the support for more than one authorization Jarkko Sakkinen
2025-12-16  9:21 ` [PATCH v8 10/12] tpm-buf: Remove tpm_buf_append_handle Jarkko Sakkinen
2025-12-16  9:21 ` [PATCH v8 11/12] tpm-buf: Merge TPM_BUF_BOUNDARY_ERROR and TPM_BUF_OVERFLOW Jarkko Sakkinen
2025-12-16  9:21 ` [PATCH v8 12/12] tpm-buf: Implement managed allocations Jarkko Sakkinen

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