From 0d6526f82c3cdefcca47f73f5fc08dc6f335eac6 Mon Sep 17 00:00:00 2001 From: Tim Chen Date: Mon, 21 Sep 2026 17:37:22 -0700 Subject: sched/cache: Keep nr_pref_llc_running in the runnable domain, to fix LLC mis-scheduling bug alb_break_llc() decides whether to break LLC preference during active load balance. It does so by testing that every runnable fair task on the source rq prefers its LLC: env->src_rq->nr_pref_llc_running == env->src_rq->cfs.h_nr_runnable But the two counters cover different sets. nr_pref_llc_running is updated in account_llc_enqueue()/account_llc_dequeue(), next to cfs_rq->nr_queued, so it follows queued tasks. h_nr_runnable is updated in set_delayed()/ clear_delayed() and drops delay-dequeued tasks. So under DELAY_DEQUEUE, a preferring task that goes to sleep stays counted in nr_pref_llc_running while h_nr_runnable falls. The equality then breaks, alb_break_llc() returns false, and active balance is free to pull a task off its preferred LLC. Active balance only moves runnable tasks, and this is the only LLC check it consults: once the stopper runs, LBF_ACTIVE_LB skips the per-task test in can_migrate_task(). The runnable set is the one we want. Fix it on the counter side. A task should be counted in nr_pref_llc_running exactly while it is both queued on its preferred LLC (pref_llc_queued) and runnable (!sched_delayed). Define that membership once in task_pref_llc_runnable(), and adjust the counter only through pref_llc_running_inc()/pref_llc_running_dec() from the four sites that change either input: account_llc_enqueue(), account_llc_dequeue(), set_delayed() and clear_delayed(). Gating every update on the same predicate keeps the delay, wake and dequeue paths from double-counting or underflowing; see the comments at those sites for the ordering. nr_llc_running and sd->llc_counts are not touched and stay on queued semantics. Fixes: 714059f79ff0 ("sched/cache: Handle moving single tasks to/from their preferred LLC") Closes: https://lore.kernel.org/lkml/20260827135000.735138-1-zhanxusheng@xiaomi.com/ Reported-by: Zhan Xusheng Suggested-by: Chen Yu Signed-off-by: Tim Chen Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Ingo Molnar Reviewed-by: Kayra Cizmeci Cc: # v7.2.x Link: https://patch.msgid.link/06af61afedac32e6477f57feb4d658f6c411c3af.1790035273.git.tim.c.chen@linux.intel.com --- drivers/firmware/efi/fdtparams.c | 133 +++++++++++++++++++++++++++++++++++++++ 1 file changed, 133 insertions(+) create mode 100644 drivers/firmware/efi/fdtparams.c (limited to 'drivers/firmware/efi/fdtparams.c') diff --git a/drivers/firmware/efi/fdtparams.c b/drivers/firmware/efi/fdtparams.c new file mode 100644 index 000000000..b815d2a75 --- /dev/null +++ b/drivers/firmware/efi/fdtparams.c @@ -0,0 +1,133 @@ +// SPDX-License-Identifier: GPL-2.0-only + +#define pr_fmt(fmt) "efi: " fmt + +#include +#include +#include +#include +#include + +#include + +enum { + SYSTAB, + MMBASE, + MMSIZE, + DCSIZE, + DCVERS, + + PARAMCOUNT +}; + +static __initconst const char name[][22] = { + [SYSTAB] = "System Table ", + [MMBASE] = "MemMap Address ", + [MMSIZE] = "MemMap Size ", + [DCSIZE] = "MemMap Desc. Size ", + [DCVERS] = "MemMap Desc. Version ", +}; + +static __initconst const struct { + const char path[17]; + u8 paravirt; + const char params[PARAMCOUNT][26]; +} dt_params[] = { + { +#ifdef CONFIG_XEN // <-------17------> + .path = "/hypervisor/uefi", + .paravirt = 1, + .params = { + [SYSTAB] = "xen,uefi-system-table", + [MMBASE] = "xen,uefi-mmap-start", + [MMSIZE] = "xen,uefi-mmap-size", + [DCSIZE] = "xen,uefi-mmap-desc-size", + [DCVERS] = "xen,uefi-mmap-desc-ver", + } + }, { +#endif + .path = "/chosen", + .params = { // <-----------26-----------> + [SYSTAB] = "linux,uefi-system-table", + [MMBASE] = "linux,uefi-mmap-start", + [MMSIZE] = "linux,uefi-mmap-size", + [DCSIZE] = "linux,uefi-mmap-desc-size", + [DCVERS] = "linux,uefi-mmap-desc-ver", + } + } +}; + +static int __init efi_get_fdt_prop(const void *fdt, int node, const char *pname, + const char *rname, void *var, int size) +{ + const void *prop; + int len; + u64 val; + + prop = fdt_getprop(fdt, node, pname, &len); + if (!prop) + return 1; + + val = (len == 4) ? (u64)be32_to_cpup(prop) : get_unaligned_be64(prop); + + if (size == 8) + *(u64 *)var = val; + else + *(u32 *)var = (val < U32_MAX) ? val : U32_MAX; // saturate + + if (efi_enabled(EFI_DBG)) + pr_info(" %s: 0x%0*llx\n", rname, size * 2, val); + + return 0; +} + +u64 __init efi_get_fdt_params(struct efi_memory_map_data *mm) +{ + const void *fdt = initial_boot_params; + unsigned long systab; + int i, j, node; + struct { + void *var; + int size; + } target[] = { + [SYSTAB] = { &systab, sizeof(systab) }, + [MMBASE] = { &mm->phys_map, sizeof(mm->phys_map) }, + [MMSIZE] = { &mm->size, sizeof(mm->size) }, + [DCSIZE] = { &mm->desc_size, sizeof(mm->desc_size) }, + [DCVERS] = { &mm->desc_version, sizeof(mm->desc_version) }, + }; + + BUILD_BUG_ON(ARRAY_SIZE(target) != ARRAY_SIZE(name)); + BUILD_BUG_ON(ARRAY_SIZE(target) != ARRAY_SIZE(dt_params[0].params)); + + if (!fdt) + return 0; + + for (i = 0; i < ARRAY_SIZE(dt_params); i++) { + node = fdt_path_offset(fdt, dt_params[i].path); + if (node < 0) + continue; + + if (efi_enabled(EFI_DBG)) + pr_info("Getting UEFI parameters from %s in DT:\n", + dt_params[i].path); + + for (j = 0; j < ARRAY_SIZE(target); j++) { + const char *pname = dt_params[i].params[j]; + + if (!efi_get_fdt_prop(fdt, node, pname, name[j], + target[j].var, target[j].size)) + continue; + if (!j) + goto notfound; + pr_err("Can't find property '%s' in DT!\n", pname); + return 0; + } + if (dt_params[i].paravirt) + set_bit(EFI_PARAVIRT, &efi.flags); + return systab; + } +notfound: + pr_info("UEFI not found.\n"); + return 0; +} -- cgit v1.3.1