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Fri, 17 Jan 2025 23:50:26 -0800 (PST) Received: from [10.4.77.142] ([118.103.63.134]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-21c2d40275csm26884805ad.215.2025.01.17.23.50.23 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 17 Jan 2025 23:50:25 -0800 (PST) Message-ID: <446f6d7c-d838-4ead-b967-5d6e52dbbb8a@daynix.com> Date: Sat, 18 Jan 2025 16:50:22 +0900 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 8/9] net/e1000e: Fix xITR minimum value To: Nicholas Piggin , qemu-devel@nongnu.org Cc: Dmitry Fleytman , Jason Wang , Sriram Yagnaraman , Fabiano Rosas , Laurent Vivier , Paolo Bonzini References: <20250117170306.403075-1-npiggin@gmail.com> <20250117170306.403075-9-npiggin@gmail.com> Content-Language: en-US From: Akihiko Odaki In-Reply-To: <20250117170306.403075-9-npiggin@gmail.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=2607:f8b0:4864:20::62a; envelope-from=akihiko.odaki@daynix.com; helo=mail-pl1-x62a.google.com X-Spam_score_int: -18 X-Spam_score: -1.9 X-Spam_bar: - X-Spam_report: (-1.9 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On 2025/01/18 2:03, Nicholas Piggin wrote: > The ITR minimum value may be a mis-reading or ambiguity in the spec. > Section 10.2.4.2 says the maximum observable interrupt rate should never > exceed 7813, but that is in context of example of the interval being > programmed to 500. On the other hand 7.4.4 does say ITR rules permit > no more than that rate. > > There is no minimum value specified, and zero is explicitly allowed and > disables throttling logic (which is already supported behaviour in the > throttling code of the models). This seems to fall outside ITR rules, so > should not cause any limit. > > Spec 7.4.4 also says that EITR registers should be initialised to zero. > > Remove the minimum value from the ITR and EITR registers, and set ITR > default to 500. > > Signed-off-by: Nicholas Piggin Please squash this change into "[PATCH 2/9] net/e1000e: Permit disabling interrupt throttling". > --- > hw/net/e1000e_core.c | 24 ++++++++++-------------- > 1 file changed, 10 insertions(+), 14 deletions(-) > > diff --git a/hw/net/e1000e_core.c b/hw/net/e1000e_core.c > index c5be20bcbbe..34bb5f8096b 100644 > --- a/hw/net/e1000e_core.c > +++ b/hw/net/e1000e_core.c > @@ -51,8 +51,13 @@ > > #include "trace.h" > > -/* No more then 7813 interrupts per second according to spec 10.2.4.2 */ > -#define E1000E_MIN_XITR (500) > +/* > + * A suggested range for ITR is 651-5580, according to spec 10.2.4.2, but > + * QEMU has traditionally set 500 here and spec 7.4.4 ITR rules says the > + * max observable interrupts from the adapter should be 7813/s (corresponding > + * to 500). > + */ > +#define E1000E_DEFAULT_ITR (500) > > #define E1000E_MAX_TX_FRAGS (64) > > @@ -2831,11 +2836,7 @@ e1000e_set_itr(E1000ECore *core, int index, uint32_t val) > trace_e1000e_irq_itr_set(val); > > core->itr_guest_value = interval; > - if (interval == 0) { > - core->mac[index] = 0; > - } else { > - core->mac[index] = MAX(interval, E1000E_MIN_XITR); > - } > + core->mac[index] = interval; > } > > static void > @@ -2847,11 +2848,7 @@ e1000e_set_eitr(E1000ECore *core, int index, uint32_t val) > trace_e1000e_irq_eitr_set(eitr_num, val); > > core->eitr_guest_value[eitr_num] = interval; > - if (interval == 0) { > - core->mac[index] = 0; > - } else { > - core->mac[index] = MAX(interval, E1000E_MIN_XITR); > - } > + core->mac[index] = interval; > } > > static void > @@ -3500,8 +3497,7 @@ static const uint32_t e1000e_mac_reg_init[] = { > [FACTPS] = E1000_FACTPS_LAN0_ON | 0x20000000, > [SWSM] = 1, > [RXCSUM] = E1000_RXCSUM_IPOFLD | E1000_RXCSUM_TUOFLD, > - [ITR] = E1000E_MIN_XITR, > - [EITR...EITR + E1000E_MSIX_VEC_NUM - 1] = E1000E_MIN_XITR, > + [ITR] = E1000E_DEFAULT_ITR, > }; > > static void e1000e_reset(E1000ECore *core, bool sw)