On Thu, Jan 10, 2019 at 07:14 Bhupesh Sharma wrote:
Hi Hedi,
Hi Bhupesh,
Thanks for the patchset.
Thanks for looking at it.
I will give this a go on my sgi-uv300 machine and come back with more detailed inputs,
and for testing it.
but I wanted to ask about the hang/panic you mentioned in the cover letter when efi_scratch gets clobbered. Can you describe the same (for e.g. how to reproduce this).
When efi_switch_mm() gets called concurrently from two different CPUs --via arch_efi_call_virt_setup()-- due to lack of serialisation in uv_bios_call(), efi_scratch.prev_mm is overwritten and that's how all hell breaks loose, and that's when you see either a hang (the more frequent failure mode) or a panic. In order to reproduce the problem you'd need, for example, a kernel module that makes use of uv_bios_call(), in which case a test case would be a loop with: - 2 concurrent tasks both invoking uv_bios_call() or - 2 concurrent tasks - one invoking uv_bios_call() - one, for example, accessing an EFI vars via efivars
Nitpicks below: On 01/09/2019 04:15 PM, Hedi Berriche wrote:Calls into UV firmware must be protected against concurrency, use the now visible efi_runtime_sem lock to serialise them. Signed-off-by: Hedi Berriche <hedi.berriche@xxxxxxx> Reviewed-by: Russ Anderson <rja@xxxxxxx> Reviewed-by: Mike Travis <mike.travis@xxxxxxx> Reviewed-by: Dimitri Sivanich <sivanich@xxxxxxx> Reviewed-by: Steve Wahl <steve.wahl@xxxxxxx> --- arch/x86/include/asm/uv/bios.h | 3 ++- arch/x86/platform/uv/bios_uv.c | 25 ++++++++++++++++++++++--- 2 files changed, 24 insertions(+), 4 deletions(-) diff --git a/arch/x86/include/asm/uv/bios.h b/arch/x86/include/asm/uv/bios.h index 4eee646544b2..33e94aa0b1ff 100644 --- a/arch/x86/include/asm/uv/bios.h +++ b/arch/x86/include/asm/uv/bios.h @@ -48,7 +48,8 @@ enum { BIOS_STATUS_SUCCESS = 0, BIOS_STATUS_UNIMPLEMENTED = -ENOSYS, BIOS_STATUS_EINVAL = -EINVAL, - BIOS_STATUS_UNAVAIL = -EBUSY + BIOS_STATUS_UNAVAIL = -EBUSY, + BIOS_STATUS_ABORT = -EINTR }; /* Address map parameters */ diff --git a/arch/x86/platform/uv/bios_uv.c b/arch/x86/platform/uv/bios_uv.c index cd05af157763..92f960798e20 100644 --- a/arch/x86/platform/uv/bios_uv.c +++ b/arch/x86/platform/uv/bios_uv.c @@ -29,7 +29,8 @@ struct uv_systab *uv_systab; -s64 uv_bios_call(enum uv_bios_cmd which, u64 a1, u64 a2, u64 a3, u64 a4, u64 a5) +s64 __uv_bios_call(enum uv_bios_cmd which, u64 a1, u64 a2, u64 a3, + u64 a4, u64 a5)Can we make this static?
Will do.
{ struct uv_systab *tab = uv_systab; s64 ret; @@ -44,13 +45,26 @@ s64 uv_bios_call(enum uv_bios_cmd which, u64 a1, u64 a2, u64 a3, u64 a4, u64 a5) * If EFI_OLD_MEMMAP is set, we need to fall back to using our old EFI * callback method, which uses efi_call() directly, with the kernel page tables: */ - if (unlikely(test_bit(EFI_OLD_MEMMAP, &efi.flags))) + if (unlikely(efi_enabled(EFI_OLD_MEMMAP))) ret = efi_call((void *)__va(tab->function), (u64)which, a1, a2, a3, a4, a5); else ret = efi_call_virt_pointer(tab, function, (u64)which, a1, a2, a3, a4, a5); return ret; } + +s64 uv_bios_call(enum uv_bios_cmd which, u64 a1, u64 a2, u64 a3, u64 a4, u64 a5) +{ + s64 ret; + + if (down_interruptible(&efi_runtime_sem)) + return BIOS_STATUS_ABORT; + + ret = __uv_bios_call(which, a1, a2, a3, a4, a5); + up(&efi_runtime_sem); + + return ret; +} EXPORT_SYMBOL_GPL(uv_bios_call); s64 uv_bios_call_irqsave(enum uv_bios_cmd which, u64 a1, u64 a2, u64 a3, @@ -59,10 +73,15 @@ s64 uv_bios_call_irqsave(enum uv_bios_cmd which, u64 a1, u64 a2, u64 a3, unsigned long bios_flags; s64 ret; + if (down_interruptible(&efi_runtime_sem)) + return BIOS_STATUS_ABORT; + local_irq_save(bios_flags); - ret = uv_bios_call(which, a1, a2, a3, a4, a5); + ret = __uv_bios_call(which, a1, a2, a3, a4, a5); local_irq_restore(bios_flags); + up(&efi_runtime_sem); + return ret; }Thanks, Bhupesh
Cheers, Hedi. -- Be careful of reading health books, you might die of a misprint. -- Mark Twain
