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Subject: Re: [RFC PATCH 10/13] x86/uintr: Introduce user IPI sender syscalls
To:     Greg KH <gregkh@linuxfoundation.org>
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References: <20210913200132.3396598-1-sohil.mehta@intel.com>
 <20210913200132.3396598-11-sohil.mehta@intel.com>
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From:   Sohil Mehta <sohil.mehta@intel.com>
Message-ID: <4704e81d-a3d2-aedf-1c79-e45cc86826a5@intel.com>
Date:   Tue, 28 Sep 2021 11:01:54 -0700
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On 9/23/2021 5:28 AM, Greg KH wrote:
> On Mon, Sep 13, 2021 at 01:01:29PM -0700, Sohil Mehta wrote:
>> +/* User Interrupt Target Table Entry (UITTE) */
>> +struct uintr_uitt_entry {
>> +	u8	valid;			/* bit 0: valid, bit 1-7: reserved */
> Do you check that the other bits are set to 0?

I don't have a check but kzalloc() in alloc_uitt() should set it to 0.

>> +	u8	user_vec;
>> +	u8	reserved[6];
> What is this reserved for?

This is hardware defined structure as well. I should probably mention 
this it in the comment above.

>> +	u64	target_upid_addr;
> If this is a pointer, why not say it is a pointer?

I used a u64 to get the size and alignment of this structure as required 
by the hardware. I wasn't sure if using a struct upid * would complicate 
that.

Also this field is never used as a pointer by the kernel. It is only 
used to program an entry that is read by the hardware.

Is this reasonable or would you still prefer a pointer?


>> +} __packed __aligned(16);
>> +
>> +struct uintr_uitt_ctx {
>> +	struct uintr_uitt_entry *uitt;
>> +	/* Protect UITT */
>> +	spinlock_t uitt_lock;
>> +	refcount_t refs;
> Again, a kref please.

Will do.

Thanks,

Sohil