From: Boaz Harrosh <boaz@plexistor.com>
To: Yigal Korman <yigal@plexistor.com>,
tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com,
x86@kernel.org, linux-kernel@vger.kernel.org
Cc: linux-nvdimm@lists.01.org
Subject: Re: [PATCH] x86/mm: only allow memmap=XX!YY over existing RAM
Date: Thu, 23 Jun 2016 14:52:08 +0300 [thread overview]
Message-ID: <576BCD68.8010500@plexistor.com> (raw)
In-Reply-To: <1466408039-7497-1-git-send-email-yigal@plexistor.com>
On 06/20/2016 10:33 AM, Yigal Korman wrote:
> Before this patch, passing a range that is beyond the physical memory
> range will succeed, the user will see a /dev/pmem0 and will be able to
> access it. Reads will always return 0 and writes will be silently
> ignored.
>
> I've gotten more than one bug report about mkfs.{xfs,ext4} or nvml
> failing that were eventually tracked down to be wrong values passed to
> memmap.
>
> This patch prevents the above issue by instead of adding a new memory
> range, only update a RAM memory range with the PRAM type. This way,
> passing the wrong memmap will either not give you a pmem at all or give
> you a smaller one that actually has RAM behind it.
>
> And if someone still needs to fake a pmem that doesn't have RAM behind
> it, they can simply do memmap=XX@YY,XX!YY.
>
We are running with this patch for a while in the lab and it does
solve the problem above with no maleffects so:
Tested-by: Boaz Harrosh <boaz@plexistor.com>
> Signed-off-by: Yigal Korman <yigal@plexistor.com>
> ---
> arch/x86/kernel/e820.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/x86/kernel/e820.c b/arch/x86/kernel/e820.c
> index 621b501..4bd4207 100644
> --- a/arch/x86/kernel/e820.c
> +++ b/arch/x86/kernel/e820.c
> @@ -878,7 +878,7 @@ static int __init parse_memmap_one(char *p)
> e820_add_region(start_at, mem_size, E820_RESERVED);
> } else if (*p == '!') {
> start_at = memparse(p+1, &p);
> - e820_add_region(start_at, mem_size, E820_PRAM);
> + e820_update_range(start_at, mem_size, E820_RAM, E820_PRAM);
> } else
> e820_remove_range(mem_size, ULLONG_MAX - mem_size, E820_RAM, 1);
>
>
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WARNING: multiple messages have this Message-ID (diff)
From: Boaz Harrosh <boaz@plexistor.com>
To: Yigal Korman <yigal@plexistor.com>,
tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com,
x86@kernel.org, linux-kernel@vger.kernel.org
Cc: linux-nvdimm@ml01.01.org
Subject: Re: [PATCH] x86/mm: only allow memmap=XX!YY over existing RAM
Date: Thu, 23 Jun 2016 14:52:08 +0300 [thread overview]
Message-ID: <576BCD68.8010500@plexistor.com> (raw)
In-Reply-To: <1466408039-7497-1-git-send-email-yigal@plexistor.com>
On 06/20/2016 10:33 AM, Yigal Korman wrote:
> Before this patch, passing a range that is beyond the physical memory
> range will succeed, the user will see a /dev/pmem0 and will be able to
> access it. Reads will always return 0 and writes will be silently
> ignored.
>
> I've gotten more than one bug report about mkfs.{xfs,ext4} or nvml
> failing that were eventually tracked down to be wrong values passed to
> memmap.
>
> This patch prevents the above issue by instead of adding a new memory
> range, only update a RAM memory range with the PRAM type. This way,
> passing the wrong memmap will either not give you a pmem at all or give
> you a smaller one that actually has RAM behind it.
>
> And if someone still needs to fake a pmem that doesn't have RAM behind
> it, they can simply do memmap=XX@YY,XX!YY.
>
We are running with this patch for a while in the lab and it does
solve the problem above with no maleffects so:
Tested-by: Boaz Harrosh <boaz@plexistor.com>
> Signed-off-by: Yigal Korman <yigal@plexistor.com>
> ---
> arch/x86/kernel/e820.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/x86/kernel/e820.c b/arch/x86/kernel/e820.c
> index 621b501..4bd4207 100644
> --- a/arch/x86/kernel/e820.c
> +++ b/arch/x86/kernel/e820.c
> @@ -878,7 +878,7 @@ static int __init parse_memmap_one(char *p)
> e820_add_region(start_at, mem_size, E820_RESERVED);
> } else if (*p == '!') {
> start_at = memparse(p+1, &p);
> - e820_add_region(start_at, mem_size, E820_PRAM);
> + e820_update_range(start_at, mem_size, E820_RAM, E820_PRAM);
> } else
> e820_remove_range(mem_size, ULLONG_MAX - mem_size, E820_RAM, 1);
>
>
next prev parent reply other threads:[~2016-06-23 11:52 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-06-20 7:33 [PATCH] x86/mm: only allow memmap=XX!YY over existing RAM Yigal Korman
2016-06-20 7:33 ` Yigal Korman
2016-06-20 14:44 ` Dan Williams
2016-06-20 14:44 ` Dan Williams
2016-06-21 12:56 ` Johannes Thumshirn
2016-06-21 12:56 ` Johannes Thumshirn
2016-06-23 11:52 ` Boaz Harrosh [this message]
2016-06-23 11:52 ` Boaz Harrosh
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