From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pl1-f201.google.com (mail-pl1-f201.google.com [209.85.214.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 2000734CFAB for ; Fri, 22 May 2026 20:24:19 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.214.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779481462; cv=none; b=FHep4nj9O2dzIOa3VOYEz9j8AhorESFrniX0yt4cLg8X7n8rrDnwLP9+S2ZOBrB1WsgDhzcPWXO/x/dElwkNt7Tdi0SOHaY4j2cXfcOtP1EhrP9etV2c4c+kRxSuk01G518C1Ljf5Bwb0YW7wcylmf/r/U+dcVPaB5SjKzppLo0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779481462; c=relaxed/simple; bh=1vV0uwLZDO9f0jwlmwTLYtqhKwT1lIDL5w/1xm9Frgg=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=kfoSGgYE6uWoVit2rIfvClsfxREVpnfXkrZbE+LAyN7I1YGJIhB3G2vk/hRpYOlRV2DEm6AawN2Jj7aNjk+/CeqOzLYgeJmJqgX5NdJWWTkUeaAXQLd4mDlMVM1459jwnAjRkXULvxljW+RrP22SX4b6gxCxcfFb/FD1dXR7ow4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--dmatlack.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=NcDjWuzF; arc=none smtp.client-ip=209.85.214.201 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--dmatlack.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="NcDjWuzF" Received: by mail-pl1-f201.google.com with SMTP id d9443c01a7336-2b4654f9bb6so79139915ad.2 for ; Fri, 22 May 2026 13:24:19 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1779481459; x=1780086259; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=SPpQo5/8o8XmqfCxBMhae2hXoPWQwl78O5LFi9BXZl8=; b=NcDjWuzF7FhT9i1SRotT/Pa9gJIO8pbN2SWkyb/Sawlftb5VDiCx9KHmwNin3YiM4q L7Q6uoykpAaHHLeYTvuaRC6s3AnoKkkLzSTqRFg/lGEkdtU3C/hpbr//ZgsCV2qQDHlU yJEvzQ/FvJtX7nFnyuz1T7Fp0azlkwLYfHGYkYhnSPoBEDEib6P7LlAipktreM4B0oMj 4MzpTp8MC2wRf1j7WpdL5hpYf8LiqdVRgyqnYhKm08HGDZhBH2n7bdyZWb3aP7ElV1TO uwmapsFhXe64pwjTX+9sZxUBNtCfI+WpwsDAa9cQzhIXHuUkvAxpctjkzQNdOlR/4guj yN7Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1779481459; x=1780086259; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=SPpQo5/8o8XmqfCxBMhae2hXoPWQwl78O5LFi9BXZl8=; b=D1oDOJlmBcWp7XiQbVUQW2iPHa/GKpopkyJtwwpy/lA5+KF+9ULQ+E/840pPsuGkRd dW9Xc2uUvotJnPOiLMkkNFYA062DoSbj4AW63OA71ra76NZcf1IfEDkg/XnOV4EPGWYC F3qRAEPSzcp8EH4vyqofBetDMqeY1eF5afao63PP3Y4L12PX6E6VTsQkWMba1b2VlBMi 1B5K0GpeIL2P5B+Mlf3nX52L6HVirZYKizXVi9awFzV4iS4q3RoNj9cLqX6xTBLNQGUX bIGOWp//GTQHD9KlWUvhjG3pgeIw28tC6Tv4je9we0u8y5smtty6798jH7LVrsijZP6G iBcA== X-Forwarded-Encrypted: i=1; AFNElJ+ORQdb0djlPmiJO5syhN4qk+2i/junHWKmH3WLLgT+1g/Wk8yeugMCxiqc1NfsaQKqWfaE8hZWMcs=@vger.kernel.org X-Gm-Message-State: AOJu0YzJ4cpDAQ9sqvrr0j9UsI7SWtLcq92iK710ZJd/GDdSuHKDMGhC L5HJwYY6OCp3nr1d1t3r4HouZwWvv1ES6uCoPnj4Ak0FaUOK790UHmi9H8PTxrsrl1jRWa/2rCf 1Du8qXQu679iLRg== X-Received: from plqu9.prod.google.com ([2002:a17:902:a609:b0:2bd:9b10:8067]) (user=dmatlack job=prod-delivery.src-stubby-dispatcher) by 2002:a17:903:354b:b0:2bc:db91:f5a7 with SMTP id d9443c01a7336-2beb0735023mr53621445ad.11.1779481459064; Fri, 22 May 2026 13:24:19 -0700 (PDT) Date: Fri, 22 May 2026 20:24:06 +0000 In-Reply-To: <20260522202410.3104264-1-dmatlack@google.com> Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20260522202410.3104264-1-dmatlack@google.com> X-Mailer: git-send-email 2.54.0.746.g67dd491aae-goog Message-ID: <20260522202410.3104264-9-dmatlack@google.com> Subject: [PATCH v6 08/12] PCI: liveupdate: Inherit ACS flags in incoming preserved devices From: David Matlack To: kexec@lists.infradead.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-pci@vger.kernel.org Cc: Adithya Jayachandran , Alexander Graf , Alex Williamson , Bjorn Helgaas , Chris Li , David Matlack , David Rientjes , Jacob Pan , Jason Gunthorpe , Jonathan Corbet , Josh Hilke , Leon Romanovsky , Lukas Wunner , Mike Rapoport , Parav Pandit , Pasha Tatashin , Pranjal Shrivastava , Pratyush Yadav , Saeed Mahameed , Samiullah Khawaja , Shuah Khan , Vipin Sharma , William Tu , Yi Liu Content-Type: text/plain; charset="UTF-8" Inherit Access Control Services (ACS) flags on all incoming preserved devices (endpoints and upstream bridges) during a Live Update. Inheriting ACS flags avoids changing routing rules while memory transactions are in flight from preserved devices. This is also strictly necessary to ensure that IOMMU group assignments do not change across a Live Update for preserved devices, as changing ACS configurations can split or merge IOMMU groups. Cache the inherited ACS controls established by the previous kernel in struct pci_dev so that ACS controls do not change after a reset (pci_restore_state() calls pci_enable_acs()). To simplify ACS inheritance, reject preserving any devices that require quirks to enable ACS as those quirks would also have to take Live Update into account. Signed-off-by: David Matlack --- drivers/pci/liveupdate.c | 68 ++++++++++++++++++++++++++++++++++ drivers/pci/liveupdate.h | 11 ++++++ drivers/pci/pci.c | 5 +++ drivers/pci/pci.h | 5 +++ drivers/pci/quirks.c | 7 ++++ include/linux/pci_liveupdate.h | 6 +++ 6 files changed, 102 insertions(+) diff --git a/drivers/pci/liveupdate.c b/drivers/pci/liveupdate.c index 4c79e19b7f98..a93b7ef065f2 100644 --- a/drivers/pci/liveupdate.c +++ b/drivers/pci/liveupdate.c @@ -71,6 +71,9 @@ * * * The device cannot be a Virtual Function (VF). * + * * The device cannot require device-specific quirks to enable Access + * Control Services (ACS). + * * Driver Binding * ============== * @@ -113,6 +116,18 @@ * This enables the PCI core and any drivers bound to the bridge to participate * in the Live Update so that preserved endpoints can continue issuing memory * transactions during the Live Update. + * + * Handling Preserved Devices + * ========================== + * + * The PCI core treats preserved devices differently than non-preserved devices. + * This section enumerates those differences. + * + * * The PCI core inherits all ACS flags enabled on incoming preserved devices + * rather than assigning new ones. This ensures that TLPs are routed the same + * way after Live Update and ensures that IOMMU groups do not change. Note + * that a device will use its inherited ACS flags for the lifetime of its + * struct pci_dev (i.e. even after pci_liveupdate_finish()). */ #define pr_fmt(fmt) "PCI: liveupdate: " fmt @@ -126,6 +141,7 @@ #include #include "liveupdate.h" +#include "pci.h" /** * struct pci_liveupdate_global - Global state for PCI Live Update support @@ -319,6 +335,16 @@ static int __pci_liveupdate_preserve_device(struct pci_ser *ser, struct pci_dev { int i; + /* + * Do not preserve devices that rely on device-specific ACS equivalents + * (for now) since that would complicate keeping ACS constant across + * Live Update. + */ + if (pci_need_dev_specific_enable_acs(dev)) { + pci_warn(dev, "Refusing to preserve device that relies on ACS quirks\n"); + return -EINVAL; + } + if (ser->nr_devices == ser->max_nr_devices) return -ENOSPC; @@ -598,6 +624,7 @@ void pci_liveupdate_setup_device(struct pci_dev *dev) pci_info(dev, "Device was preserved by previous kernel across Live Update\n"); dev->liveupdate.incoming = dev_ser; + dev->liveupdate.was_preserved = true; /* * Hold the ref on the incoming FLB until pci_liveupdate_finish() so @@ -688,6 +715,47 @@ void pci_liveupdate_finish(struct pci_dev *dev) } EXPORT_SYMBOL_GPL(pci_liveupdate_finish); +void pci_liveupdate_init_acs(struct pci_dev *dev) +{ + guard(rwsem_read)(&pci_liveupdate.rwsem); + + if (!dev->acs_cap || !dev->liveupdate.incoming) + return; + + pci_read_config_word(dev, dev->acs_cap + PCI_ACS_CTRL, &dev->liveupdate.acs_ctrl); +} + +int pci_liveupdate_enable_acs(struct pci_dev *dev) +{ + u16 acs_ctrl = dev->liveupdate.acs_ctrl; + u16 acs_cap = dev->acs_cap; + + /* + * Use liveupdate.was_preserved instead of liveupdate.incoming since the + * device's ACS controls should not change even after the device is + * finished participating in the Live Update. + */ + if (!dev->liveupdate.was_preserved) + return -EINVAL; + + /* + * The previous kernel should not have preserved any devices that + * require device-specific quirks to enable ACS, but if such a device is + * detected, log a big warning and fall back to the normal enable ACS + * path. + */ + if (pci_need_dev_specific_enable_acs(dev)) { + pci_warn(dev, "Device-specific quirk required to enable ACS!\n"); + WARN_ON_ONCE(true); + return -EINVAL; + } + + if (acs_cap) + pci_write_config_word(dev, acs_cap + PCI_ACS_CTRL, acs_ctrl); + + return 0; +} + /** * pci_liveupdate_is_incoming() - Check if a device is incoming-preserved * @dev: The PCI device to check diff --git a/drivers/pci/liveupdate.h b/drivers/pci/liveupdate.h index c763255a8de4..4e8a01bcb4bb 100644 --- a/drivers/pci/liveupdate.h +++ b/drivers/pci/liveupdate.h @@ -16,6 +16,8 @@ void pci_liveupdate_cleanup_device(struct pci_dev *dev); bool pci_liveupdate_scan_bridge_begin(struct pci_bus *bus, struct pci_dev *dev, int pass); void pci_liveupdate_scan_bridge_end(struct pci_dev *dev, int pass); +void pci_liveupdate_init_acs(struct pci_dev *dev); +int pci_liveupdate_enable_acs(struct pci_dev *dev); #else static inline void pci_liveupdate_setup_device(struct pci_dev *dev) { @@ -35,6 +37,15 @@ static inline bool pci_liveupdate_scan_bridge_begin(struct pci_bus *bus, static inline void pci_liveupdate_scan_bridge_end(struct pci_dev *dev, int pass) { } + +static inline void pci_liveupdate_init_acs(struct pci_dev *dev) +{ +} + +static inline int pci_liveupdate_enable_acs(struct pci_dev *dev) +{ + return -EINVAL; +} #endif #endif /* DRIVERS_PCI_LIVEUPDATE_H */ diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c index 8f7cfcc00090..211df4618164 100644 --- a/drivers/pci/pci.c +++ b/drivers/pci/pci.c @@ -33,6 +33,7 @@ #include #include #include +#include "liveupdate.h" #include "pci.h" DEFINE_MUTEX(pci_slot_mutex); @@ -1017,6 +1018,9 @@ void pci_enable_acs(struct pci_dev *dev) bool enable_acs = false; int pos; + if (!pci_liveupdate_enable_acs(dev)) + return; + /* If an iommu is present we start with kernel default caps */ if (pci_acs_enable) { if (pci_dev_specific_enable_acs(dev)) @@ -3657,6 +3661,7 @@ void pci_acs_init(struct pci_dev *dev) pci_read_config_word(dev, pos + PCI_ACS_CAP, &dev->acs_capabilities); pci_disable_broken_acs_cap(dev); + pci_liveupdate_init_acs(dev); } /** diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h index 4a14f88e543a..b55f3deddd57 100644 --- a/drivers/pci/pci.h +++ b/drivers/pci/pci.h @@ -1062,6 +1062,7 @@ void pci_acs_init(struct pci_dev *dev); void pci_enable_acs(struct pci_dev *dev); #ifdef CONFIG_PCI_QUIRKS int pci_dev_specific_acs_enabled(struct pci_dev *dev, u16 acs_flags); +bool pci_need_dev_specific_enable_acs(struct pci_dev *dev); int pci_dev_specific_enable_acs(struct pci_dev *dev); int pci_dev_specific_disable_acs_redir(struct pci_dev *dev); void pci_disable_broken_acs_cap(struct pci_dev *pdev); @@ -1072,6 +1073,10 @@ static inline int pci_dev_specific_acs_enabled(struct pci_dev *dev, { return -ENOTTY; } +static inline bool pci_need_dev_specific_enable_acs(struct pci_dev *dev) +{ + return false; +} static inline int pci_dev_specific_enable_acs(struct pci_dev *dev) { return -ENOTTY; diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c index 171caec2bc47..59b0b19c3783 100644 --- a/drivers/pci/quirks.c +++ b/drivers/pci/quirks.c @@ -5482,6 +5482,13 @@ static const struct pci_dev_acs_ops *pci_dev_acs_ops_get(struct pci_dev *dev) return NULL; } +bool pci_need_dev_specific_enable_acs(struct pci_dev *dev) +{ + const struct pci_dev_acs_ops *p = pci_dev_acs_ops_get(dev); + + return p && p->enable_acs; +} + int pci_dev_specific_enable_acs(struct pci_dev *dev) { const struct pci_dev_acs_ops *p = pci_dev_acs_ops_get(dev); diff --git a/include/linux/pci_liveupdate.h b/include/linux/pci_liveupdate.h index 2be98819e313..2446c6d237ca 100644 --- a/include/linux/pci_liveupdate.h +++ b/include/linux/pci_liveupdate.h @@ -17,14 +17,20 @@ * struct pci_liveupdate - PCI Live Update state for a struct pci_dev * @outgoing: State preserved for the next kernel. * @incoming: State preserved by the previous kernel. + * @acs_ctrl: ACS features established by the previous kernel. * @inherit_buses: True if the PCI core should inherit the secondary and * subordinate bus numbers assigned to this device due to * an ongoing Live Update. + * @was_preserved: True if this struct pci_dev was preserved by the previous + * kernel. Unlike @incoming, this field is not cleared after + * the device is finished participating in Live Update. */ struct pci_liveupdate { struct pci_dev_ser *outgoing; struct pci_dev_ser *incoming; + u16 acs_ctrl; bool inherit_buses; + bool was_preserved; }; struct pci_dev; -- 2.54.0.746.g67dd491aae-goog