Remove MDS command line option since it can be set using the common
clar_cpu_buffers parameter.

Signed-off-by: Daniel Sneddon <daniel.sneddon@linux.intel.com>
---
 .../admin-guide/kernel-parameters.txt         | 32 -------------------
 arch/x86/kernel/cpu/bugs.c                    | 21 ------------
 2 files changed, 53 deletions(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 66b567c4dce5..2753a1e51da5 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -3231,38 +3231,6 @@
 			Format: <first>,<last>
 			Specifies range of consoles to be captured by the MDA.
 
-	mds=		[X86,INTEL,EARLY]
-			Control mitigation for the Micro-architectural Data
-			Sampling (MDS) vulnerability.
-
-			Certain CPUs are vulnerable to an exploit against CPU
-			internal buffers which can forward information to a
-			disclosure gadget under certain conditions.
-
-			In vulnerable processors, the speculatively
-			forwarded data can be used in a cache side channel
-			attack, to access data to which the attacker does
-			not have direct access.
-
-			This parameter controls the MDS mitigation. The
-			options are:
-
-			full       - Enable MDS mitigation on vulnerable CPUs
-			full,nosmt - Enable MDS mitigation and disable
-				     SMT on vulnerable CPUs
-			off        - Unconditionally disable MDS mitigation
-
-			On TAA-affected machines, mds=off can be prevented by
-			an active TAA mitigation as both vulnerabilities are
-			mitigated with the same mechanism so in order to disable
-			this mitigation, you need to specify tsx_async_abort=off
-			too.
-
-			Not specifying this option is equivalent to
-			mds=full.
-
-			For details see: Documentation/admin-guide/hw-vuln/mds.rst
-
 	mem=nn[KMG]	[HEXAGON,EARLY] Set the memory size.
 			Must be specified, otherwise memory size will be 0.
 
diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index b3c9e1eede12..ed5524bc3ee4 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -261,27 +261,6 @@ static void __init mds_select_mitigation(void)
 	}
 }
 
-static int __init mds_cmdline(char *str)
-{
-	if (!boot_cpu_has_bug(X86_BUG_MDS))
-		return 0;
-
-	if (!str)
-		return -EINVAL;
-
-	if (!strcmp(str, "off"))
-		mds_mitigation = MDS_MITIGATION_OFF;
-	else if (!strcmp(str, "full"))
-		mds_mitigation = MDS_MITIGATION_FULL;
-	else if (!strcmp(str, "full,nosmt")) {
-		mds_mitigation = MDS_MITIGATION_FULL;
-		mds_nosmt = true;
-	}
-
-	return 0;
-}
-early_param("mds", mds_cmdline);
-
 #undef pr_fmt
 #define pr_fmt(fmt)	"TAA: " fmt
 
-- 
2.25.1

On 9/24/24 15:31, Daniel Sneddon wrote:
> -	mds=		[X86,INTEL,EARLY]
> -			Control mitigation for the Micro-architectural Data
> -			Sampling (MDS) vulnerability.

As much as I'd love to remove old code, won't this surprise users if we
just take this away?

I suspect the _least_ we can do is warn folks if they use something that
we recently ripped out.  But the right thing is probably to keep the old
one around for at least a while. <sigh>

On 9/24/24 15:34, Dave Hansen wrote:
> On 9/24/24 15:31, Daniel Sneddon wrote:
>> -	mds=		[X86,INTEL,EARLY]
>> -			Control mitigation for the Micro-architectural Data
>> -			Sampling (MDS) vulnerability.
> 
> As much as I'd love to remove old code, won't this surprise users if we
> just take this away?
> 
> I suspect the _least_ we can do is warn folks if they use something that
> we recently ripped out.  But the right thing is probably to keep the old
> one around for at least a while. <sigh>

True. I can leave the functionality but print a message basically saying "Don't
use this use the new one".

Thanks,
Dan