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From: Jarkko Sakkinen <jarkko@kernel.org>
To: ira.weiny@intel.com
Cc: Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
	x86@kernel.org, Sean Christopherson <seanjc@google.com>,
	Jethro Beekman <jethro@fortanix.com>,
	Dave Hansen <dave.hansen@intel.com>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	linux-sgx@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] x86/sgx: Remove unnecessary kmap() from sgx_ioc_enclave_init()
Date: Fri, 26 Mar 2021 21:45:24 +0200	[thread overview]
Message-ID: <YF451PGNd8x/i56z@kernel.org> (raw)
In-Reply-To: <20210324182246.2484875-1-ira.weiny@intel.com>

On Wed, Mar 24, 2021 at 11:22:46AM -0700, ira.weiny@intel.com wrote:
> From: Ira Weiny <ira.weiny@intel.com>
> 
> kmap is inefficient and is being replaced by kmap_local_page(), if
> possible.

Nit: just saying that something is inefficient is not enough. Always
should have something to back it up.

> That said, there is no readily apparent reason why initp_page needs to
> be allocated and kmap'ed() except that 'sigstruct' needs to be page
> aligned and 'token' 512 byte aligned.
> 
> Rather than change this kmap() to kmap_local_page() use kmalloc()
> instead because kmalloc() can gives this alignment when allocating
> PAGE_SIZE bytes.
> 
> Remove the alloc_page()/kmap() and replace with kmalloc(PAGE_SIZE, ...)
> to get a page aligned kernel address.
> 
> In addition add a comment to document the alignment requirements so that
> others don't attempt to 'fix' this again.

I'm a bit confused based on this commit message. Why is kmap_local_page()
better, and why kmalloc() is the ultimate choice of all three options?

> 
> Cc: Sean Christopherson <seanjc@google.com>
> Cc: Jethro Beekman <jethro@fortanix.com>
> Cc: Jarkko Sakkinen <jarkko@kernel.org>
> Cc: Dave Hansen <dave.hansen@intel.com>
> Signed-off-by: Ira Weiny <ira.weiny@intel.com>
 
/Jarkko

      parent reply	other threads:[~2021-03-26 19:46 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-24 18:22 [PATCH] x86/sgx: Remove unnecessary kmap() from sgx_ioc_enclave_init() ira.weiny
2021-03-25  9:07 ` [tip: x86/sgx] " tip-bot2 for Ira Weiny
2021-03-26 19:45 ` Jarkko Sakkinen [this message]

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