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[175.34.62.5]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2981185e3a0sm60642025ad.45.2025.11.10.20.05.25 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 10 Nov 2025 20:05:28 -0800 (PST) Message-ID: Date: Tue, 11 Nov 2025 14:05:23 +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> Content-Language: en-US From: Gavin Shan In-Reply-To: <20251110151107.5e825ea0@fedora> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=170.10.129.124; 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=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 Hi Igor, 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 ? >> 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