linux-kernel - Re: [PATCH v5 2/2] x86/sgx: Add an attribute for the amount of SGX memory in a NUMA node

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Message-ID: <254864594af4cde213a37a4db527e293a1ef1d7a.camel@kernel.org>
Date:   Thu, 23 Sep 2021 23:30:14 +0300
From:   Jarkko Sakkinen <jarkko@...nel.org>
To:     Reinette Chatre <reinette.chatre@...el.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        x86@...nel.org, "H. Peter Anvin" <hpa@...or.com>,
        Jonathan Corbet <corbet@....net>
Cc:     linux-sgx@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-doc@...r.kernel.org
Subject: Re: [PATCH v5 2/2] x86/sgx: Add an attribute for the amount of SGX
 memory in a NUMA node

On Wed, 2021-09-22 at 16:30 -0700, Reinette Chatre wrote:
> Hi Jarkko,
> 
> On 9/13/2021 8:04 PM, Jarkko Sakkinen wrote:
> > The amount of SGX memory on the system is determined by the BIOS and it
> > varies wildly between systems.  It can be from dozens of MB's on desktops
> > or VM's, up to many GB's on servers.  Just like for regular memory, it is
> > sometimes useful to know the amount of usable SGX memory in the system.
> > 
> > Add an attribute for the amount of SGX memory in bytes to each NUMA
> > node. The path is /sys/devices/system/node/node[0-9]*/sgx/memory_size.
> > 
> > Signed-off-by: Jarkko Sakkinen <jarkko@...nel.org>
> > 
> > ---
> > v5: A new patch based on the discussion at
> >      https://lore.kernel.org/linux-sgx/3a7cab4115b4f902f3509ad8652e616b91703e1d.camel@kernel.org/T/#t
> > ---
> >   Documentation/x86/sgx.rst      | 14 ++++++
> >   arch/x86/kernel/cpu/sgx/main.c | 90 ++++++++++++++++++++++++++++++++++
> >   arch/x86/kernel/cpu/sgx/sgx.h  |  2 +
> >   3 files changed, 106 insertions(+)
> > 
> 
> ...
> 
> > diff --git a/arch/x86/kernel/cpu/sgx/main.c b/arch/x86/kernel/cpu/sgx/main.c
> > index a6e313f1a82d..c43b5a0120c1 100644
> > --- a/arch/x86/kernel/cpu/sgx/main.c
> > +++ b/arch/x86/kernel/cpu/sgx/main.c
> > @@ -717,6 +717,7 @@ static bool __init sgx_page_cache_init(void)
> >   		}
> >   
> >   		sgx_epc_sections[i].node =  &sgx_numa_nodes[nid];
> > +		sgx_numa_nodes[nid].size += size;
> >   
> >   		sgx_nr_epc_sections++;
> >   	}
> 
> The above memory seems to be uninitialized at the time it is incremented.
> 
> I tried this out on a system that reports the following:
> 
> $ dmesg | grep EPC
> [    7.252838] sgx: EPC section 0x1000c00000-0x107f7fffff
> [    7.256921] sgx: EPC section 0x2000c00000-0x207fffffff
> 
> It shows unexpectedly large values:
> $ cat /sys/devices/system/node/node*/sgx/memory_size
> 12421486739271732874
> 16308428754864105707
> 
> System reported sane values after adding this fixup:
> 
> diff --git a/arch/x86/kernel/cpu/sgx/main.c b/arch/x86/kernel/cpu/sgx/main.c
> index 3380390cc052..d73bbfbfc05d 100644
> --- a/arch/x86/kernel/cpu/sgx/main.c
> +++ b/arch/x86/kernel/cpu/sgx/main.c
> @@ -621,7 +621,7 @@ static bool __init sgx_page_cache_init(void)
>   	int nid;
>   	int i;
> 
> -	sgx_numa_nodes = kmalloc_array(num_possible_nodes(), 
> sizeof(*sgx_numa_nodes), GFP_KERNEL);
> +	sgx_numa_nodes = kcalloc(num_possible_nodes(), 
> sizeof(*sgx_numa_nodes), GFP_KERNEL);
>   	if (!sgx_numa_nodes)
>   		return false;
> 
> 
> After fixup:
> $ cat /sys/devices/system/node/node*/sgx/memory_size
> 2126512128
> 2134900736

Thanks! I did not experience in a VM.

So cat you pick these patches to your patch set, and squash
this fix to it?


/Jarkko