From: Dave Hansen <dave.hansen@linux.intel.com>
To: linux-kernel@vger.kernel.org
Cc: Dave Hansen <dave.hansen@linux.intel.com>,
David Binderman <dcb314@hotmail.com>,
Andy Lutomirski <luto@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
x86@kernel.org
Subject: [PATCH] x86/mm: Simplify redundant overlap calculation
Date: Tue, 23 Jan 2024 08:36:23 -0800 [thread overview]
Message-ID: <20240123163623.1342917-1-dave.hansen@linux.intel.com> (raw)
There have been a couple of reports that the two sides of the
overlaps() calculation are redundant. I spent way too much time
looking at this, but I became convinced that they are redundant
when a little test program of mine produced identical disassembly
for both versions of the check.
Remove the second condition. It is exactly the same as the first.
Fixes: 91ee8f5c1f50 ("x86/mm/cpa: Allow range check for static protections")
Reported-by: David Binderman <dcb314@hotmail.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: x86@kernel.org
---
arch/x86/mm/pat/set_memory.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)
diff --git a/arch/x86/mm/pat/set_memory.c b/arch/x86/mm/pat/set_memory.c
index e9b448d1b1b70..fdc00516c0b54 100644
--- a/arch/x86/mm/pat/set_memory.c
+++ b/arch/x86/mm/pat/set_memory.c
@@ -435,8 +435,7 @@ static void cpa_flush(struct cpa_data *data, int cache)
static bool overlaps(unsigned long r1_start, unsigned long r1_end,
unsigned long r2_start, unsigned long r2_end)
{
- return (r1_start <= r2_end && r1_end >= r2_start) ||
- (r2_start <= r1_end && r2_end >= r1_start);
+ return (r1_start <= r2_end && r1_end >= r2_start);
}
#ifdef CONFIG_PCI_BIOS
--
2.34.1
next reply other threads:[~2024-01-23 16:36 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-01-23 16:36 Dave Hansen [this message]
2024-01-23 16:47 ` [PATCH] x86/mm: Simplify redundant overlap calculation Dave Hansen
2024-01-23 16:54 ` David Binderman
2024-01-23 17:00 ` Dave Hansen
2024-01-23 19:19 ` Sohil Mehta
2024-01-23 19:28 ` Sohil Mehta
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