[+to Rafael, probably the logical place to apply this] On Mon, Sep 18, 2023 at 01:07:45PM +0000, Shiju Jose wrote: > >-----Original Message----- > >From: Bjorn Helgaas <helgaas@xxxxxxxxxx> > > ... > >On Sat, Sep 16, 2023 at 01:44:35AM +0800, shiju.jose@xxxxxxxxxx wrote: > >> From: Shiju Jose <shiju.jose@xxxxxxxxxx> > >> > >> ghes_handle_aer() lacks synchronization with > >> aer_recover_work_func(), so when error status data have multiple > >> sections, aer_recover_work_func() may use estatus data for > >> aer_capability_regs after it has been overwritten. > >> > >> The problem statement is here, > >> https://lore.kernel.org/all/20230901225755.GA90053@bhelgaas/ > >> > >> In ghes_handle_aer() allocates memory for aer_capability_regs from the > >> ghes_estatus_pool and copy data for aer_capability_regs from the > >> estatus buffer. Free the memory in aer_recover_work_func() after > >> processing the data using the ghes_estatus_pool_region_free() added. > > > >Thanks for working this up! I had it on my to-do list, but > >obviously had not gotten to it yet. > > > >> Reported-by: Bjorn Helgaas <helgaas@xxxxxxxxxx> > >> Signed-off-by: Shiju Jose <shiju.jose@xxxxxxxxxx> > >> --- > >> drivers/acpi/apei/ghes.c | 23 ++++++++++++++++++++++- > >> drivers/pci/pcie/aer.c | 10 ++++++++++ > >> include/acpi/ghes.h | 1 + > >> 3 files changed, 33 insertions(+), 1 deletion(-) > >> > >> diff --git a/drivers/acpi/apei/ghes.c b/drivers/acpi/apei/ghes.c index > >> ef59d6ea16da..63ad0541db38 100644 > >> --- a/drivers/acpi/apei/ghes.c > >> +++ b/drivers/acpi/apei/ghes.c > >> @@ -209,6 +209,20 @@ int ghes_estatus_pool_init(unsigned int num_ghes) > >> return -ENOMEM; > >> } > >> > >> +/** > >> + * ghes_estatus_pool_region_free - free previously allocated memory > >> + * from the ghes_estatus_pool. > >> + * @addr: address of memory to free. > >> + * @size: size of memory to free. > >> + * > >> + * Returns none. > >> + */ > >> +void ghes_estatus_pool_region_free(unsigned long addr, u32 size) { > >> + gen_pool_free(ghes_estatus_pool, addr, size); } > >> +EXPORT_SYMBOL_GPL(ghes_estatus_pool_region_free); > >> + > >> static int map_gen_v2(struct ghes *ghes) { > >> return > >> apei_map_generic_address(&ghes->generic_v2->read_ack_register); > >> @@ -564,6 +578,7 @@ static void ghes_handle_aer(struct acpi_hest_generic_data *gdata) > >> pcie_err->validation_bits & CPER_PCIE_VALID_AER_INFO) { > >> unsigned int devfn; > >> int aer_severity; > >> + u8 *aer_info; > >> > >> devfn = PCI_DEVFN(pcie_err->device_id.device, > >> pcie_err->device_id.function); > >> @@ -577,11 +592,17 @@ static void ghes_handle_aer(struct acpi_hest_generic_data *gdata) > >> if (gdata->flags & CPER_SEC_RESET) > >> aer_severity = AER_FATAL; > >> > >> + aer_info = (void *)gen_pool_alloc(ghes_estatus_pool, > >> + sizeof(struct aer_capability_regs)); > >> + if (!aer_info) > >> + return; > >> + memcpy(aer_info, pcie_err->aer_info, sizeof(struct > >> +aer_capability_regs)); > > > >This is a very straightforward approach to fixing this, and it looks pretty > >reasonable, although I'd rather not have to pull more GHES stuff into aer.c > >(ghes.h and ghes_estatus_pool_region_free()). > > > >What I had in mind was to put a queue of aer_capability_regs on the PCI side > >that could be used by both the APEI path and the native path. > > > >In the APEI path, platform firmware reads the error information from the > >hardware, and it feeds into PCI AER via aer_recover_queue(). > > > >In the native path, Linux should be reading reads the same error information > >from the hardware, but it feeds into PCI AER quite differently, via > >aer_process_err_devices() and handle_error_source(). > > > >These paths are fundamentally doing the exact same thing, but the data > >handling and dmesg logging are needlessly different. I'd like to see them get a > >little more unified, so the native path could someday also feed into > >aer_recover_queue(). > > > >Does that make any sense? > > Thanks for letting us know. > Make sense, solution with in the AER looks better. Thanks for considering this. The AER rework I have in mind is a longer-term project, so unless you have time and interest in doing that, I think we should apply your patch since it's all ready to go. You pointed to the problem statement, but I think it would be good to include a brief outline directly in the commit log, e.g., something like this: ghes_handle_aer() passes AER data to the PCI core for logging and recovery by calling aer_recover_queue() with a pointer to struct aer_capability_regs. The problem was that aer_recover_queue() queues the pointer directly without copying the aer_capability_regs data. The pointer was to the ghes->estatus buffer, which could be reused before aer_recover_work_func() reads the data. To avoid this problem, allocate a new aer_capability_regs structure from the ghes_estatus_pool, copy the AER data from the ghes->estatus buffer into it, pass a pointer to the new struct to aer_recover_queue(), and free it after aer_recover_work_func() has processed it. What's your take on this, Rafael? The biggest change is in drivers/acpi, so if you want to take it, feel free to add my: Acked-by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx> > >> aer_recover_queue(pcie_err->device_id.segment, > >> pcie_err->device_id.bus, > >> devfn, aer_severity, > >> (struct aer_capability_regs *) > >> - pcie_err->aer_info); > >> + aer_info); > >> } > >> #endif > >> } > >> diff --git a/drivers/pci/pcie/aer.c b/drivers/pci/pcie/aer.c index > >> e85ff946e8c8..388b614c11fd 100644 > >> --- a/drivers/pci/pcie/aer.c > >> +++ b/drivers/pci/pcie/aer.c > >> @@ -29,6 +29,7 @@ > >> #include <linux/kfifo.h> > >> #include <linux/slab.h> > >> #include <acpi/apei.h> > >> +#include <acpi/ghes.h> > >> #include <ras/ras_event.h> > >> > >> #include "../pci.h" > >> @@ -996,6 +997,15 @@ static void aer_recover_work_func(struct work_struct > >*work) > >> continue; > >> } > >> cper_print_aer(pdev, entry.severity, entry.regs); > >> + /* > >> + * Memory for aer_capability_regs(entry.regs) is being > >allocated from the > >> + * ghes_estatus_pool to protect it from overwriting when > >multiple sections > >> + * are present in the error status. Thus free the same after > >processing > >> + * the data. > >> + */ > >> + ghes_estatus_pool_region_free((unsigned long)entry.regs, > >> + sizeof(struct aer_capability_regs)); > >> + > >> if (entry.severity == AER_NONFATAL) > >> pcie_do_recovery(pdev, pci_channel_io_normal, > >> aer_root_reset); > >> diff --git a/include/acpi/ghes.h b/include/acpi/ghes.h index > >> 3c8bba9f1114..40d89e161076 100644 > >> --- a/include/acpi/ghes.h > >> +++ b/include/acpi/ghes.h > >> @@ -78,6 +78,7 @@ static inline struct list_head > >> *ghes_get_devices(void) { return NULL; } #endif > >> > >> int ghes_estatus_pool_init(unsigned int num_ghes); > >> +void ghes_estatus_pool_region_free(unsigned long addr, u32 size); > >> > >> static inline int acpi_hest_get_version(struct acpi_hest_generic_data > >> *gdata) { > >> -- > >> 2.34.1 > >> > > Thanks, > Shiju
