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[175.34.62.5]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-343eac7ec56sm48384a91.10.2025.11.12.09.41.08 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 12 Nov 2025 09:41:12 -0800 (PST) Message-ID: <54de65b4-6ba3-474a-b9b2-e128cfc9f2ef@redhat.com> Date: Thu, 13 Nov 2025 03:41:06 +1000 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 2/8] acpi/ghes: Increase GHES raw data maximal length to 4KiB To: Igor Mammedov Cc: qemu-arm@nongnu.org, qemu-devel@nongnu.org, jonathan.cameron@huawei.com, mchehab+huawei@kernel.org, gengdongjiu1@gmail.com, mst@redhat.com, anisinha@redhat.com, peter.maydell@linaro.org, pbonzini@redhat.com, shan.gavin@gmail.com References: <20251105114453.2164073-1-gshan@redhat.com> <20251105114453.2164073-3-gshan@redhat.com> <20251110151107.5e825ea0@fedora> <20251112133217.41cc6df8@fedora> Content-Language: en-US From: Gavin Shan In-Reply-To: <20251112133217.41cc6df8@fedora> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=170.10.133.124; envelope-from=gshan@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_VALIDITY_CERTIFIED_BLOCKED=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=unavailable 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 Hi Igor, On 11/12/25 10:32 PM, Igor Mammedov wrote: > On Tue, 11 Nov 2025 14:05:23 +1000 > Gavin Shan wrote: >> On 11/11/25 12:11 AM, Igor Mammedov wrote: >>> On Wed, 5 Nov 2025 21:44:47 +1000 >>> Gavin Shan wrote: >>> >>>> The current GHES raw data maximal length isn't enough for 16 consecutive >>>> CPER errors, which will be sent to a guest with 4KiB page size on a >>>> erroneous 64KiB host page. Note those 16 CPER errors will be contained >>>> in one single error block, meaning all CPER errors should be identical >>>> in terms of type and severity and all of them should be delivered in >>>> one shot. >>>> >>>> Increase GHES raw data maximal length from 1KiB to 4KiB so that the >>>> error block has enough storage space for 16 consecutive CPER errors. >>>> >>>> Signed-off-by: Gavin Shan >>>> --- >>>> docs/specs/acpi_hest_ghes.rst | 2 +- >>>> hw/acpi/ghes.c | 2 +- >>>> 2 files changed, 2 insertions(+), 2 deletions(-) >>>> >>>> diff --git a/docs/specs/acpi_hest_ghes.rst b/docs/specs/acpi_hest_ghes.rst >>>> index aaf7b1ad11..acf31d6eeb 100644 >>>> --- a/docs/specs/acpi_hest_ghes.rst >>>> +++ b/docs/specs/acpi_hest_ghes.rst >>>> @@ -68,7 +68,7 @@ Design Details >>>> and N Read Ack Register entries. The size for each entry is 8-byte. >>>> The Error Status Data Block table contains N Error Status Data Block >>>> entries. The size for each entry is defined at the source code as >>>> - ACPI_GHES_MAX_RAW_DATA_LENGTH (currently 1024 bytes). The total size >>>> + ACPI_GHES_MAX_RAW_DATA_LENGTH (currently 4096 bytes). The total size >>> >>> is it safe to bump without compat glue? >>> >>> consider VM migrated from old QEMU to new one, >>> it will have etc/hardware_errors allocated with 1K GESB, >>> and more importantly error_block_addressN will have 1K offsets as well >>> >>> however with ACPI_GHES_MAX_RAW_DATA_LENGTH all length checks will >>> let >1K blocks to be written into into 1K 'formated' etc/hardware_errors. >>> >>> Thanks to previous refactoring we get all addresses right (1K version), >>> but if you write large GESB there it will either overlap with the next GESB >>> or a smaller GESB might overwrite tail of preceding large one. >>> And in works case it's OOB when writing large GESB in the last block. >>> >>> Given we have to write GESB successfully or abort, there is no point >>> in adding compat knobs. But we still need to check if GEBS will fit into >>> whatever block size etc/hardware_errors inside guest RAM is laid out originally. >>> >> >> Good point. You're right that we're not safe for migration from old QEMU to >> and new QEMU. So I think I need to bump vmstate_hest_state::minimum_version_id >> in generic_event_device.c ? > > that won't help, > what would help is creating compat property (in the owner of GHES MMIO registers), > and lower limits (to former value) for older machine types. > That way sizes would match even if you do ping pong migration > between old qemu and new one, since one would still be using old machine type > for that. > In v4, a compat property 'x-error-block-size' has been added, as the fence between QEMU 10.1 and 10.2 (1KiB vs 4KiB GHES error block size). https://lists.nongnu.org/archive/html/qemu-arm/2025-11/msg00534.html >> >> >>>> for the "etc/hardware_errors" fw_cfg blob is >>>> (N * 8 * 2 + N * ACPI_GHES_MAX_RAW_DATA_LENGTH) bytes. >>>> N is the number of the kinds of hardware error sources. >>>> diff --git a/hw/acpi/ghes.c b/hw/acpi/ghes.c >>>> index 06555905ce..a9c08e73c0 100644 >>>> --- a/hw/acpi/ghes.c >>>> +++ b/hw/acpi/ghes.c >>>> @@ -33,7 +33,7 @@ >>>> #define ACPI_HEST_ADDR_FW_CFG_FILE "etc/acpi_table_hest_addr" >>>> >>>> /* The max size in bytes for one error block */ >>>> -#define ACPI_GHES_MAX_RAW_DATA_LENGTH (1 * KiB) >>>> +#define ACPI_GHES_MAX_RAW_DATA_LENGTH (4 * KiB) >>>> >>>> /* Generic Hardware Error Source version 2 */ >>>> #define ACPI_GHES_SOURCE_GENERIC_ERROR_V2 10 >> Thanks, Gavin