Re: [PATCH 3/3] x86/platform/UV: use efi_runtime_sem to serialise BIOS calls

[Bhupesh Sharma]

Hi Hedi,

Thanks for the patchset.
I will give this a go on my sgi-uv300 machine and come back with more 
detailed inputs, 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).

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.berri...@hpe.com>
Reviewed-by: Russ Anderson <r...@hpe.com>
Reviewed-by: Mike Travis <mike.tra...@hpe.com>
Reviewed-by: Dimitri Sivanich <sivan...@hpe.com>
Reviewed-by: Steve Wahl <steve.w...@hpe.com>
---
  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?

  {
        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