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Mon, 12 Oct 2026 11:48:47 -0700 (PDT) From: Magnus Lindholm To: davem@davemloft.net, andreas@gaisler.com, sparclinux@vger.kernel.org Cc: linux-kernel@vger.kernel.org, gregkh@linuxfoundation.org, jirislaby@kernel.org, linux-serial@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, krzk@kernel.org, oleg@redhat.com, linmag7@gmail.com, stable@vger.kernel.org Subject: [PATCH v3 2/8] sparc64: honor queued spinlock layout in secondary startup Date: Mon, 12 Oct 2026 20:48:03 +0200 Message-ID: <20261012184826.986050-3-linmag7@gmail.com> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20261012184826.986050-1-linmag7@gmail.com> References: <20261012184826.986050-1-linmag7@gmail.com> Precedence: bulk X-Mailing-List: linux-serial@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit The trampoline's ldstub modifies the queue-tail byte of prom_entry_lock, not its locked byte, because SPARC64 uses big-endian queued spinlocks. Acquire the word with CASA, release byte three and poll while contended. Retain the predicted-branch barriers for Spitfire erratum 51. See qspinlock_types.h for the layout and JPS2 A.10/A.35 for CASA/MEMBAR. Fixes: 145d97858597 ("arch/sparc: Enable queued spinlock support for SPARC") Cc: stable@vger.kernel.org Signed-off-by: Magnus Lindholm --- arch/sparc/kernel/trampoline_64.S | 34 +++++++++++++++++++++++++++---- 1 file changed, 30 insertions(+), 4 deletions(-) diff --git a/arch/sparc/kernel/trampoline_64.S b/arch/sparc/kernel/trampoline_64.S index 51bf1eb92a36..62f404b3079a 100644 --- a/arch/sparc/kernel/trampoline_64.S +++ b/arch/sparc/kernel/trampoline_64.S @@ -106,9 +106,19 @@ startup_continue: * We lock 'num_kernel_image_mappings' consequetive entries. */ sethi %hi(prom_entry_lock), %g2 -1: ldstub [%g2 + %lo(prom_entry_lock)], %g1 + /* Big-endian qspinlock: acquire the whole 32-bit value, not byte 0. */ + or %g2, %lo(prom_entry_lock), %g2 +1: lduw [%g2], %g1 brnz,pn %g1, 1b nop + mov 1, %g1 + casa [%g2] ASI_P, %g0, %g1 + brnz,pn %g1, 1b + nop + /* Spitfire erratum 51: barrier in a predicted-taken delay slot. */ + ba,pt %xcc, 2f + membar #Sync +2: /* Get onto temporary stack which will be in the locked * kernel image. @@ -212,7 +222,10 @@ startup_continue: nop sethi %hi(prom_entry_lock), %g2 - stb %g0, [%g2 + %lo(prom_entry_lock)] + /* Match membar_safe() for Spitfire erratum 51. */ + ba,pt %xcc, 2f + membar #StoreStore | #LoadStore +2: stb %g0, [%g2 + %lo(prom_entry_lock) + 3] ba,pt %xcc, after_lock_tlb nop @@ -326,9 +339,19 @@ after_lock_tlb: wrpr %g0, 0, %wstate sethi %hi(prom_entry_lock), %g2 -1: ldstub [%g2 + %lo(prom_entry_lock)], %g1 + /* Big-endian qspinlock: acquire the whole 32-bit value, not byte 0. */ + or %g2, %lo(prom_entry_lock), %g2 +1: lduw [%g2], %g1 brnz,pn %g1, 1b nop + mov 1, %g1 + casa [%g2] ASI_P, %g0, %g1 + brnz,pn %g1, 1b + nop + /* Spitfire erratum 51: barrier in a predicted-taken delay slot. */ + ba,pt %xcc, 2f + membar #Sync +2: /* As a hack, put &init_thread_union into %g6. * prom_world() loads from here to restore the %asi @@ -389,7 +412,10 @@ after_lock_tlb: add %sp, (2047 + 128), %o0 3: sethi %hi(prom_entry_lock), %g2 - stb %g0, [%g2 + %lo(prom_entry_lock)] + /* Match membar_safe() for Spitfire erratum 51. */ + ba,pt %xcc, 2f + membar #StoreStore | #LoadStore +2: stb %g0, [%g2 + %lo(prom_entry_lock) + 3] ldx [%l0], %g6 ldx [%g6 + TI_TASK], %g4