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Date: Sat, 18 Jan 2020 23:13:38 +0800
From: Jiaxun Yang <jiaxun.yang@...goat.com>
To: Philippe Mathieu-Daudé <f4bug@...at.org>
Cc: "open list:BROADCOM NVRAM DRIVER" <linux-mips@...r.kernel.org>,
Huacai Chen <chenhc@...ote.com>,
Paul Burton <paul.burton@...s.com>,
open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] MIPS: Introduce aligned IO memory operations
18.01.2020, 22:41, "Philippe Mathieu-Daudé" <f4bug@...at.org>:
> Hi Jiaxun,
>
> On Tue, Jan 14, 2020 at 1:24 PM Jiaxun Yang <jiaxun.yang@...goat.com> wrote:
>> Some platforms, such as Loongson64 or QEMU/KVM, don't support unaligned
>> instructions like lwl or lwr in IO memory access. However, our current
>> IO memcpy/memset is wired to the generic implementation, which leads
>> to a fatal result.
>
> Do you have a handy reproducer to try with QEMU/KVM?
It was triggered by QXL DRM driver when I was working on KVM for Loongson
with Huacai.
See arch/mips/kvm/emulate.c, we didn't have unaligned instructions trap
emulation for MMIO. You can construct a simple unaligned memcpy_fromio
case to reproduce it.
Thanks.
>
>> Signed-off-by: Jiaxun Yang <jiaxun.yang@...goat.com>
>> ---
>> arch/mips/Kconfig | 4 ++
>> arch/mips/include/asm/io.h | 10 ++++
>> arch/mips/kernel/Makefile | 2 +-
>> arch/mips/kernel/io.c | 98 ++++++++++++++++++++++++++++++++++++++
>> 4 files changed, 113 insertions(+), 1 deletion(-)
>> create mode 100644 arch/mips/kernel/io.c
>>
>> diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
>> index 8b0cd692a43f..15a331aa23a2 100644
>> --- a/arch/mips/Kconfig
>> +++ b/arch/mips/Kconfig
>> @@ -1450,6 +1450,7 @@ config CPU_LOONGSON64
>> select CPU_SUPPORTS_HIGHMEM
>> select CPU_SUPPORTS_HUGEPAGES
>> select CPU_SUPPORTS_MSA
>> + select CPU_NEEDS_ALIGNED_IO
>> select CPU_HAS_LOAD_STORE_LR
>> select CPU_DIEI_BROKEN if !LOONGSON3_ENHANCEMENT
>> select CPU_MIPSR2_IRQ_VI
>> @@ -2598,6 +2599,9 @@ config CPU_HAS_LOAD_STORE_LR
>> LWL, LWR, SWL, SWR (Load/store word left/right).
>> LDL, LDR, SDL, SDR (Load/store doubleword left/right, for 64bit systems).
>>
>> +config CPU_NEEDS_ALIGNED_IO
>> + bool
>> +
>> #
>> # Vectored interrupt mode is an R2 feature
>> #
>> diff --git a/arch/mips/include/asm/io.h b/arch/mips/include/asm/io.h
>> index 3f6ce74335b4..3b0eb4941f23 100644
>> --- a/arch/mips/include/asm/io.h
>> +++ b/arch/mips/include/asm/io.h
>> @@ -577,6 +577,15 @@ BUILDSTRING(l, u32)
>> BUILDSTRING(q, u64)
>> #endif
>>
>> +#if defined(CONFIG_CPU_NEEDS_ALIGNED_IO)
>> +extern void __memcpy_fromio(void *, const volatile void __iomem *, size_t);
>> +extern void __memcpy_toio(volatile void __iomem *, const void *, size_t);
>> +extern void __memset_io(volatile void __iomem *, int, size_t);
>> +
>> +#define memset_io(c, v, l) __memset_io((c), (v), (l))
>> +#define memcpy_fromio(a, c, l) __memcpy_fromio((a), (c), (l))
>> +#define memcpy_toio(c, a, l) __memcpy_toio((c), (a), (l))
>> +#else
>> static inline void memset_io(volatile void __iomem *addr, unsigned char val, int count)
>> {
>> memset((void __force *) addr, val, count);
>> @@ -589,6 +598,7 @@ static inline void memcpy_toio(volatile void __iomem *dst, const void *src, int
>> {
>> memcpy((void __force *) dst, src, count);
>> }
>> +#endif
>>
>> /*
>> * The caches on some architectures aren't dma-coherent and have need to
>> diff --git a/arch/mips/kernel/Makefile b/arch/mips/kernel/Makefile
>> index d6e97df51cfb..b07b97b9385e 100644
>> --- a/arch/mips/kernel/Makefile
>> +++ b/arch/mips/kernel/Makefile
>> @@ -8,7 +8,7 @@ extra-y := head.o vmlinux.lds
>> obj-y += cmpxchg.o cpu-probe.o branch.o elf.o entry.o genex.o idle.o irq.o \
>> process.o prom.o ptrace.o reset.o setup.o signal.o \
>> syscall.o time.o topology.o traps.o unaligned.o watch.o \
>> - vdso.o cacheinfo.o
>> + vdso.o cacheinfo.o io.o
>>
>> ifdef CONFIG_FUNCTION_TRACER
>> CFLAGS_REMOVE_ftrace.o = -pg
>> diff --git a/arch/mips/kernel/io.c b/arch/mips/kernel/io.c
>> new file mode 100644
>> index 000000000000..ca105aa76d4d
>> --- /dev/null
>> +++ b/arch/mips/kernel/io.c
>> @@ -0,0 +1,98 @@
>> +// SPDX-License-Identifier: GPL-2.0-or-later
>> +
>> +#include <linux/export.h>
>> +#include <linux/types.h>
>> +#include <linux/io.h>
>> +
>> +#if defined(CONFIG_CPU_NEEDS_ALIGNED_IO)
>> +
>> +#if defined(CONFIG_64BIT)
>> +#define IO_LONG_READ __raw_readq
>> +#define IO_LONG_WRITE __raw_writeq
>> +#define IO_LONG_SIZE 8
>> +#else
>> +#define IO_LONG_READ __raw_readl
>> +#define IO_LONG_WRITE __raw_writel
>> +#define IO_LONG_SIZE 4
>> +#endif
>> +
>> +void __memcpy_fromio(void *to, const volatile void __iomem *from, size_t count)
>> +{
>> + while (count && !IS_ALIGNED((unsigned long)from, IO_LONG_SIZE) &&
>> + !IS_ALIGNED((unsigned long)to, IO_LONG_SIZE)) {
>> + *(u8 *)to = __raw_readb(from);
>> + from++;
>> + to++;
>> + count--;
>> + }
>> +
>> + while (count >= IO_LONG_SIZE) {
>> + *(unsigned long *)to = IO_LONG_READ(from);
>> + from += IO_LONG_SIZE;
>> + to += IO_LONG_SIZE;
>> + count -= IO_LONG_SIZE;
>> + }
>> +
>> + while (count) {
>> + *(u8 *)to = __raw_readb(from);
>> + from++;
>> + to++;
>> + count--;
>> + }
>> +}
>> +EXPORT_SYMBOL(__memcpy_fromio);
>> +
>> +void __memcpy_toio(volatile void __iomem *to, const void *from, size_t count)
>> +{
>> + while (count && !IS_ALIGNED((unsigned long)from, IO_LONG_SIZE) &&
>> + !IS_ALIGNED((unsigned long)to, IO_LONG_SIZE)) {
>> + __raw_writeb(*(u8 *)from, to);
>> + from++;
>> + to++;
>> + count--;
>> + }
>> +
>> + while (count >= IO_LONG_SIZE) {
>> + IO_LONG_WRITE(*(unsigned long *)from, to);
>> + from += IO_LONG_SIZE;
>> + to += IO_LONG_SIZE;
>> + count -= IO_LONG_SIZE;
>> + }
>> +
>> + while (count) {
>> + __raw_writeb(*(u8 *)from, to);
>> + from++;
>> + to++;
>> + count--;
>> + }
>> +}
>> +EXPORT_SYMBOL(__memcpy_toio);
>> +
>> +void __memset_io(volatile void __iomem *dst, int c, size_t count)
>> +{
>> + unsigned long lc = (u8)c;
>> + int i;
>> +
>> + for (i = 1; i < IO_LONG_SIZE; i++)
>> + lc |= (u8)c << (i * BITS_PER_BYTE);
>> +
>> + while (count && !IS_ALIGNED((unsigned long)dst, IO_LONG_SIZE)) {
>> + __raw_writeb((u8)c, dst);
>> + dst++;
>> + count--;
>> + }
>> +
>> + while (count >= IO_LONG_SIZE) {
>> + IO_LONG_WRITE(lc, dst);
>> + dst += IO_LONG_SIZE;
>> + count -= IO_LONG_SIZE;
>> + }
>> +
>> + while (count) {
>> + __raw_writeb(c, dst);
>> + dst++;
>> + count--;
>> + }
>> +}
>> +EXPORT_SYMBOL(__memset_io);
>> +#endif
>> --
>> 2.24.1
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