linux-kernel - Re: [PATCH 3/3] platform/x86/intel/ifs: Disable irq during one load stage

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Date: Fri, 12 Apr 2024 12:13:58 -0700
From: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@...ux.intel.com>
To: Jithu Joseph <jithu.joseph@...el.com>, ilpo.jarvinen@...ux.intel.com,
 hdegoede@...hat.com, markgross@...nel.org
Cc: linux-kernel@...r.kernel.org, platform-driver-x86@...r.kernel.org,
 ashok.raj@...el.com, tony.luck@...el.com, rostedt@...dmis.org,
 ravi.v.shankar@...el.com, patches@...ts.linux.dev
Subject: Re: [PATCH 3/3] platform/x86/intel/ifs: Disable irq during one load
 stage


On 4/12/24 10:23 AM, Jithu Joseph wrote:
> One of the stages in IFS image loading process involves loading individual
> chunks (test patterns) from test image file to secure memory.
>
> Driver issues a WRMSR(MSR_AUTHENTICATE_AND_COPY_CHUNK) operation to do
> this. This operation can take up to 5 msec, and if an interrupt occurs
> in between, the AUTH_AND_COPY_CHUNK u-code implementation aborts the
> operation.
>
> Interrupt sources such as NMI or SMI are handled by retrying. Regular
> interrupts may occur frequently enough to prevent this operation from ever
> completing. Disable irq on local cpu around the aforementioned WRMSR to
> allow the operation to complete.
>
> Signed-off-by: Jithu Joseph <jithu.joseph@...el.com>
> Reviewed-by: Tony Luck <tony.luck@...el.com>
> Reviewed-by: Ashok Raj <ashok.raj@...el.com>
> ---


Looks good to me.

Reviewed-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@...ux.intel.com>


>  drivers/platform/x86/intel/ifs/load.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/drivers/platform/x86/intel/ifs/load.c b/drivers/platform/x86/intel/ifs/load.c
> index 584c44387e10..39f19cb51749 100644
> --- a/drivers/platform/x86/intel/ifs/load.c
> +++ b/drivers/platform/x86/intel/ifs/load.c
> @@ -233,7 +233,9 @@ static int copy_hashes_authenticate_chunks_gen2(struct device *dev)
>  		chunk_table[0] = starting_chunk_nr + i;
>  		chunk_table[1] = linear_addr;
>  		do {
> +			local_irq_disable();
>  			wrmsrl(MSR_AUTHENTICATE_AND_COPY_CHUNK, (u64)chunk_table);
> +			local_irq_enable();
>  			rdmsrl(MSR_CHUNKS_AUTHENTICATION_STATUS, chunk_status.data);
>  			err_code = chunk_status.error_code;
>  		} while (err_code == AUTH_INTERRUPTED_ERROR && --retry_count);

-- 
Sathyanarayanan Kuppuswamy
Linux Kernel Developer