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[35.205.13.209]) by smtp.gmail.com with ESMTPSA id ada2fe7eead31-60582e73126sm434180137.4.2026.04.01.10.10.03 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 01 Apr 2026 10:10:04 -0700 (PDT) Date: Wed, 1 Apr 2026 17:09:49 +0000 From: Sebastian Ene To: Sudeep Holla Cc: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, android-kvm@google.com Subject: Re: [PATCH] firmware: arm_ffa: Use the correct buffer size during RXTX_MAP Message-ID: References: <20260401111738.323647-1-sebastianene@google.com> <20260401-agile-agouti-of-atheism-cb342c@sudeepholla> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20260401-agile-agouti-of-atheism-cb342c@sudeepholla> On Wed, Apr 01, 2026 at 05:21:02PM +0100, Sudeep Holla wrote: > On Wed, Apr 01, 2026 at 11:17:38AM +0000, Sebastian Ene wrote: > > Don't use the discovered buffer size from an FFA_FEATURES call directly > > since we can run on a system that has the PAGE_SIZE larger than the > > returned size which makes the alloc_pages_exact for the buffer to be > > rounded up. > > > > Fixes: 61824feae5c0 ("firmware: arm_ffa: Fetch the Rx/Tx buffer size using ffa_features()") > > Signed-off-by: Sebastian Ene > > --- > > drivers/firmware/arm_ffa/driver.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/drivers/firmware/arm_ffa/driver.c b/drivers/firmware/arm_ffa/driver.c > > index f2f94d4d533e..d0c926aca120 100644 > > --- a/drivers/firmware/arm_ffa/driver.c > > +++ b/drivers/firmware/arm_ffa/driver.c > > @@ -2078,7 +2078,7 @@ static int __init ffa_init(void) > > > > ret = ffa_rxtx_map(virt_to_phys(drv_info->tx_buffer), > > virt_to_phys(drv_info->rx_buffer), > > - rxtx_bufsz / FFA_PAGE_SIZE); > > + DIV_ROUND_UP(rxtx_bufsz, PAGE_SIZE) / FFA_PAGE_SIZE); > > Did you mean to use PAGE_ALIGN() instead of DIV_ROUND_UP() ? Yes, PAGE_ALIGN() my bad, I will send a v2 for this. > > The new pg_cnt calculation is dimensionally incorrect and evaluates to 0 for > all the supported buffer sizes, so FFA_RXTX_MAP is always called with an > invalid page count. > > Example: with rxtx_bufsz = 4K, the expression becomes 1 / 4096 on 4K/16K/64K > page kernel, so pg_cnt == 0. Wouldn’t this cause a boot-time regression for > FF-A driver init ? Have you tested this ? I am trying to understand what I > might be missing here. > Thanks, Sebastian > -- > Regards, > Sudeep