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Subject: Re: [PATCH 3/3] x86/platform/UV: use efi_runtime_sem to serialise
 BIOS calls
To:     Hedi Berriche <hedi.berriche@hpe.com>,
        Ard Biesheuvel <ard.biesheuvel@linaro.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        "H. Peter Anvin" <hpa@zytor.com>
Cc:     x86@kernel.org, linux-efi@vger.kernel.org,
        linux-kernel@vger.kernel.org, Russ Anderson <rja@hpe.com>,
        Mike Travis <mike.travis@hpe.com>,
        Dimitri Sivanich <sivanich@hpe.com>,
        Steve Wahl <steve.wahl@hpe.com>, bhsharma@redhat.com,
        Bhupesh SHARMA <bhupesh.linux@gmail.com>
References: <20190109104541.25733-1-hedi.berriche@hpe.com>
 <20190109104541.25733-4-hedi.berriche@hpe.com>
From:   Bhupesh Sharma <bhsharma@redhat.com>
Message-ID: <134565bb-0f5e-27c7-199c-af6132dc0dc3@redhat.com>
Date:   Thu, 10 Jan 2019 12:43:38 +0530
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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.berriche@hpe.com>
> Reviewed-by: Russ Anderson <rja@hpe.com>
> Reviewed-by: Mike Travis <mike.travis@hpe.com>
> Reviewed-by: Dimitri Sivanich <sivanich@hpe.com>
> Reviewed-by: Steve Wahl <steve.wahl@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