From 4b22c693e325af075d78069e25d6c17cb102c73e Mon Sep 17 00:00:00 2001 From: Matt Redfearn Date: Thu, 1 Sep 2016 17:30:09 +0100 Subject: [PATCH] MIPS: traps: Ensure full EBase is written On CPUs which support the EBase WG (write gate) flag, the most significant bits of the exception base can be changed. Firmware running on a VP(E) using MIPS rproc may change EBase to point into the user segment where the firmware is located such that it can service interrupts. When control is transferred back to the kernel the EBase must be switched back into the kernel segment, such that the kernel's exception vectors are used. Similarly when vectored interrupts (vint) or vectored external interrupt controllers (veic) are enabled an exception vector is allocated from bootmem, and written to the EBase register. Due to the WG flag being clear, only bits 29:12 will be written. Asside from the rproc case above this is normally fine (as it will usually be a low allocation within the KSeg0 range, however when Enhanced Virtual Addressing (EVA) is enabled the allocation may be outside of the traditional KSeg0/KSeg1 address range, resulting in the wrong EBase being written. Correct both cases (configure_exception_vector() for the boot CPU, and per_cpu_trap_init() for secondary CPUs) to write EBase with the WG flag first if supported. On the Malta EVA configuration, KSeg0 is mapped to physical address 0, and memory is allocated from the KUSeg segment which is mapped to physical address 0x80000000, which physically aliases the RAM at 0. This only worked due to the exception base address aliasing the same underlying RAM that was written to & cache flushed, and due to flush_icache_range() going beyond the call of duty and flushing from the L2 cache too (due to the differing physical addresses). Signed-off-by: Matt Redfearn Signed-off-by: James Hogan Cc: Leonid Yegoshin Cc: linux-mips@linux-mips.org Patchwork: https://patchwork.linux-mips.org/patch/14150/ Signed-off-by: Ralf Baechle --- arch/mips/kernel/traps.c | 19 ++++++++++++++++++- 1 file changed, 18 insertions(+), 1 deletion(-) diff --git a/arch/mips/kernel/traps.c b/arch/mips/kernel/traps.c index edc0c3d8e386..0c0270c29cd1 100644 --- a/arch/mips/kernel/traps.c +++ b/arch/mips/kernel/traps.c @@ -2092,6 +2092,14 @@ static void configure_exception_vector(void) { if (cpu_has_veic || cpu_has_vint) { unsigned long sr = set_c0_status(ST0_BEV); + /* If available, use WG to set top bits of EBASE */ + if (cpu_has_ebase_wg) { +#ifdef CONFIG_64BIT + write_c0_ebase_64(ebase | MIPS_EBASE_WG); +#else + write_c0_ebase(ebase | MIPS_EBASE_WG); +#endif + } write_c0_ebase(ebase); write_c0_status(sr); /* Setting vector spacing enables EI/VI mode */ @@ -2128,8 +2136,17 @@ void per_cpu_trap_init(bool is_boot_cpu) * We shouldn't trust a secondary core has a sane EBASE register * so use the one calculated by the boot CPU. */ - if (!is_boot_cpu) + if (!is_boot_cpu) { + /* If available, use WG to set top bits of EBASE */ + if (cpu_has_ebase_wg) { +#ifdef CONFIG_64BIT + write_c0_ebase_64(ebase | MIPS_EBASE_WG); +#else + write_c0_ebase(ebase | MIPS_EBASE_WG); +#endif + } write_c0_ebase(ebase); + } cp0_compare_irq_shift = CAUSEB_TI - CAUSEB_IP; cp0_compare_irq = (read_c0_intctl() >> INTCTLB_IPTI) & 7; -- 2.20.1