linux-kernel - Re: [PATCH v4] x86: Remove unnecessary kmap() from sgx_ioc_enclave

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Message-ID: <YCBY02iEKLVyj7Ix@kernel.org>
Date:   Sun, 7 Feb 2021 23:17:07 +0200
From:   Jarkko Sakkinen <jarkko@...nel.org>
To:     ira.weiny@...el.com
Cc:     Dave Hansen <dave.hansen@...el.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Jethro Beekman <jethro@...tanix.com>,
        linux-kernel@...r.kernel.org, linux-sgx@...r.kernel.org
Subject: Re: [PATCH v4] x86: Remove unnecessary kmap() from
 sgx_ioc_enclave_init()

On Fri, Feb 05, 2021 at 09:00:30AM -0800, ira.weiny@...el.com wrote:
> From: Ira Weiny <ira.weiny@...el.com>
> 
> kmap is inefficient and we are trying to reduce the usage in the kernel.
> There is no readily apparent reason why initp_page needs to be allocated
> and kmap'ed() but sigstruct needs to be page aligned and token
> 512 byte aligned.
> 
> kmalloc() can give us this alignment but we need to allocate PAGE_SIZE
> bytes to do so.  Rather than change this kmap() to kmap_local_page() use
> kmalloc() instead.
> 
> Remove the alloc_page()/kmap() and replace with kmalloc(PAGE_SIZE, ...)
> to get a page aligned kernel address to use.
> 
> In addition add a comment to document the alignment requirements so that
> others like myself don't attempt to 'fix' this again.
> 
> Cc: Dave Hansen <dave.hansen@...el.com>
> Cc: Sean Christopherson <seanjc@...gle.com>
> Cc: Jethro Beekman <jethro@...tanix.com>
> Signed-off-by: Ira Weiny <ira.weiny@...el.com>

Reviewed-by: Jarkko Sakkinen <jarkko@...nel.org>

/Jarkko