Hello,
On Wed, Sep 16, 2020 at 10:52:27PM +0530, Ganesh Goudar wrote:
> To test machine check handling, add debugfs interface to inject
> slb multihit errors.
>
> To inject slb multihit:
> #echo 1 > /sys/kernel/debug/powerpc/mce_error_inject/inject_slb_multihit
>
> Signed-off-by: Ganesh Goudar <ganes...@linux.ibm.com>
> Signed-off-by: Mahesh Salgaonkar <mah...@linux.vnet.ibm.com>
> ---
> arch/powerpc/Kconfig.debug | 9 ++
> arch/powerpc/sysdev/Makefile | 2 +
> arch/powerpc/sysdev/mce_error_inject.c | 148 +++++++++++++++++++++++++
> 3 files changed, 159 insertions(+)
> create mode 100644 arch/powerpc/sysdev/mce_error_inject.c
>
> diff --git a/arch/powerpc/Kconfig.debug b/arch/powerpc/Kconfig.debug
> index b88900f4832f..61db133f2f0d 100644
> --- a/arch/powerpc/Kconfig.debug
> +++ b/arch/powerpc/Kconfig.debug
> @@ -398,3 +398,12 @@ config KASAN_SHADOW_OFFSET
> hex
> depends on KASAN
> default 0xe0000000
> +
> +config MCE_ERROR_INJECT
> + bool "Enable MCE error injection through debugfs"
> + depends on DEBUG_FS
> + default y
> + help
> + This option creates an mce_error_inject directory in the
> + powerpc debugfs directory that allows limited injection of
> + Machine Check Errors (MCEs).
> diff --git a/arch/powerpc/sysdev/Makefile b/arch/powerpc/sysdev/Makefile
> index 026b3f01a991..7fc102222b77 100644
> --- a/arch/powerpc/sysdev/Makefile
> +++ b/arch/powerpc/sysdev/Makefile
> @@ -52,3 +52,5 @@ obj-$(CONFIG_PPC_XICS) += xics/
> obj-$(CONFIG_PPC_XIVE) += xive/
>
> obj-$(CONFIG_GE_FPGA) += ge/
> +
> +obj-$(CONFIG_MCE_ERROR_INJECT) += mce_error_inject.o
> diff --git a/arch/powerpc/sysdev/mce_error_inject.c
> b/arch/powerpc/sysdev/mce_error_inject.c
> new file mode 100644
> index 000000000000..ca4726bfa2d9
> --- /dev/null
> +++ b/arch/powerpc/sysdev/mce_error_inject.c
> @@ -0,0 +1,148 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Machine Check Exception injection code
> + */
> +
> +#include <linux/kernel.h>
> +#include <linux/slab.h>
> +#include <linux/vmalloc.h>
> +#include <linux/fs.h>
> +#include <linux/debugfs.h>
> +#include <asm/debugfs.h>
> +
> +static inline unsigned long get_slb_index(void)
> +{
> + unsigned long index;
> +
> + index = get_paca()->stab_rr;
> +
> + /*
> + * simple round-robin replacement of slb starting at SLB_NUM_BOLTED.
> + */
> + if (index < (mmu_slb_size - 1))
> + index++;
> + else
> + index = SLB_NUM_BOLTED;
> + get_paca()->stab_rr = index;
> + return index;
> +}
> +
> +#define slb_esid_mask(ssize) \
> + (((ssize) == MMU_SEGSIZE_256M) ? ESID_MASK : ESID_MASK_1T)
> +
> +static inline unsigned long mk_esid_data(unsigned long ea, int ssize,
> + unsigned long slot)
> +{
> + return (ea & slb_esid_mask(ssize)) | SLB_ESID_V | slot;
> +}
> +
> +#define slb_vsid_shift(ssize) \
> + ((ssize) == MMU_SEGSIZE_256M ? SLB_VSID_SHIFT : SLB_VSID_SHIFT_1T)
> +
> +static inline unsigned long mk_vsid_data(unsigned long ea, int ssize,
> + unsigned long flags)
> +{
> + return (get_kernel_vsid(ea, ssize) << slb_vsid_shift(ssize)) | flags |
> + ((unsigned long)ssize << SLB_VSID_SSIZE_SHIFT);
> +}
> +
> +static void insert_slb_entry(char *p, int ssize)
> +{
> + unsigned long flags, entry;
> + struct paca_struct *paca;
> +
> + flags = SLB_VSID_KERNEL | mmu_psize_defs[MMU_PAGE_64K].sllp;
> +
> + preempt_disable();
> +
> + paca = get_paca();
This seems unused?
> +
> + entry = get_slb_index();
> + asm volatile("slbmte %0,%1" :
> + : "r" (mk_vsid_data((unsigned long)p, ssize, flags)),
> + "r" (mk_esid_data((unsigned long)p, ssize, entry))
> + : "memory");
> +
> + entry = get_slb_index();
> + asm volatile("slbmte %0,%1" :
> + : "r" (mk_vsid_data((unsigned long)p, ssize, flags)),
> + "r" (mk_esid_data((unsigned long)p, ssize, entry))
> + : "memory");
> + preempt_enable();
> + p[0] = '!';
> +}
> +
> +static void inject_vmalloc_slb_multihit(void)
> +{
> + char *p;
> +
> + p = vmalloc(2048);
> + if (!p)
> + return;
> +
> + insert_slb_entry(p, MMU_SEGSIZE_1T);
> + vfree(p);
> +}
> +
> +static void inject_kmalloc_slb_multihit(void)
> +{
> + char *p;
> +
> + p = kmalloc(2048, GFP_KERNEL);
> + if (!p)
> + return;
> +
> + insert_slb_entry(p, MMU_SEGSIZE_1T);
> + kfree(p);
> +}
> +
> +static ssize_t inject_slb_multihit(const char __user *u_buf, size_t count)
> +{
> + char buf[32];
> + size_t buf_size;
> +
> + buf_size = min(count, (sizeof(buf) - 1));
> + if (copy_from_user(buf, u_buf, buf_size))
> + return -EFAULT;
> + buf[buf_size] = '\0';
> +
> + if (buf[0] != '1')
> + return -EINVAL;
> +
> + inject_vmalloc_slb_multihit();
> + inject_kmalloc_slb_multihit();
This is missing the test of multihit in paca which is for some reason
special.
Thanks
Michal
> + return count;
> +}
> +
> +static ssize_t inject_write(struct file *file, const char __user *buf,
> + size_t count, loff_t *ppos)
> +{
> + static ssize_t (*func)(const char __user *, size_t);
> +
> + func = file->f_inode->i_private;
> + return func(buf, count);
> +}
> +
> +static const struct file_operations inject_fops = {
> + .write = inject_write,
> + .llseek = default_llseek,
> +};
> +
> +static int mce_error_inject_setup(void)
> +{
> + struct dentry *mce_error_inject_dir;
> +
> + mce_error_inject_dir = debugfs_create_dir("mce_error_inject",
> + powerpc_debugfs_root);
> +
> + if (mmu_has_feature(MMU_FTR_HPTE_TABLE)) {
> + (void)debugfs_create_file("inject_slb_multihit", 0200,
> + mce_error_inject_dir,
> + &inject_slb_multihit,
> + &inject_fops);
> + }
> +
> + return 0;
> +}
> +
> +device_initcall(mce_error_inject_setup);
> --
> 2.26.2
>
