linux-kernel - [tip: x86/cache] x86/cpufeatures: Add support for L3 Smart Data Cache Injection Allocation Enforcement

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Message-ID: <176382652244.498.3703313676953019180.tip-bot2@tip-bot2>
Date: Sat, 22 Nov 2025 15:48:42 -0000
From: "tip-bot2 for Babu Moger" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: Babu Moger <babu.moger@....com>, "Borislav Petkov (AMD)" <bp@...en8.de>,
 Reinette Chatre <reinette.chatre@...el.com>, x86@...nel.org,
 linux-kernel@...r.kernel.org
Subject: [tip: x86/cache] x86/cpufeatures: Add support for L3 Smart Data Cache
 Injection Allocation Enforcement

The following commit has been merged into the x86/cache branch of tip:

Commit-ID:     3767def18f4cc394dc98cb93e78c3cc9afc4c515
Gitweb:        https://git.kernel.org/tip/3767def18f4cc394dc98cb93e78c3cc9afc4c515
Author:        Babu Moger <babu.moger@....com>
AuthorDate:    Wed, 12 Nov 2025 18:57:27 -06:00
Committer:     Borislav Petkov (AMD) <bp@...en8.de>
CommitterDate: Fri, 21 Nov 2025 22:03:07 +01:00

x86/cpufeatures: Add support for L3 Smart Data Cache Injection Allocation Enforcement

Smart Data Cache Injection (SDCI) is a mechanism that enables direct insertion
of data from I/O devices into the L3 cache. By directly caching data from I/O
devices rather than first storing the I/O data in DRAM, SDCI reduces demands on
DRAM bandwidth and reduces latency to the processor consuming the I/O data.

The SDCIAE (SDCI Allocation Enforcement) PQE feature allows system software to
control the portion of the L3 cache used for SDCI.

When enabled, SDCIAE forces all SDCI lines to be placed into the L3 cache
partitions identified by the highest-supported L3_MASK_n register, where n is
the maximum supported CLOSID.

Add CPUID feature bit that can be used to configure SDCIAE.

The SDCIAE feature details are documented in:

  AMD64 Architecture Programmer's Manual Volume 2: System Programming
     Publication # 24593 Revision 3.41 section 19.4.7 L3 Smart Data Cache
    Injection Allocation Enforcement (SDCIAE).

available at https://bugzilla.kernel.org/show_bug.cgi?id=206537

Signed-off-by: Babu Moger <babu.moger@....com>
Signed-off-by: Borislav Petkov (AMD) <bp@...en8.de>
Reviewed-by: Reinette Chatre <reinette.chatre@...el.com>
Acked-by: Borislav Petkov (AMD) <bp@...en8.de>
Link: https://patch.msgid.link/83ca10d981c48e86df2c3ad9658bb3ba3544c763.1762995456.git.babu.moger@amd.com
---
 arch/x86/include/asm/cpufeatures.h | 2 ++
 arch/x86/kernel/cpu/cpuid-deps.c   | 1 +
 arch/x86/kernel/cpu/scattered.c    | 1 +
 3 files changed, 4 insertions(+)

diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
index 4091a77..2abee3e 100644
--- a/arch/x86/include/asm/cpufeatures.h
+++ b/arch/x86/include/asm/cpufeatures.h
@@ -500,6 +500,8 @@
 #define X86_FEATURE_ABMC		(21*32+15) /* Assignable Bandwidth Monitoring Counters */
 #define X86_FEATURE_MSR_IMM		(21*32+16) /* MSR immediate form instructions */
 
+#define X86_FEATURE_SDCIAE		(21*32+18) /* L3 Smart Data Cache Injection Allocation Enforcement */
+
 /*
  * BUG word(s)
  */
diff --git a/arch/x86/kernel/cpu/cpuid-deps.c b/arch/x86/kernel/cpu/cpuid-deps.c
index 46efcbd..87e7858 100644
--- a/arch/x86/kernel/cpu/cpuid-deps.c
+++ b/arch/x86/kernel/cpu/cpuid-deps.c
@@ -72,6 +72,7 @@ static const struct cpuid_dep cpuid_deps[] = {
 	{ X86_FEATURE_CQM_MBM_LOCAL,		X86_FEATURE_CQM_LLC   },
 	{ X86_FEATURE_BMEC,			X86_FEATURE_CQM_MBM_TOTAL   },
 	{ X86_FEATURE_BMEC,			X86_FEATURE_CQM_MBM_LOCAL   },
+	{ X86_FEATURE_SDCIAE,			X86_FEATURE_CAT_L3    },
 	{ X86_FEATURE_AVX512_BF16,		X86_FEATURE_AVX512VL  },
 	{ X86_FEATURE_AVX512_FP16,		X86_FEATURE_AVX512BW  },
 	{ X86_FEATURE_ENQCMD,			X86_FEATURE_XSAVES    },
diff --git a/arch/x86/kernel/cpu/scattered.c b/arch/x86/kernel/cpu/scattered.c
index caa4dc8..d113863 100644
--- a/arch/x86/kernel/cpu/scattered.c
+++ b/arch/x86/kernel/cpu/scattered.c
@@ -53,6 +53,7 @@ static const struct cpuid_bit cpuid_bits[] = {
 	{ X86_FEATURE_SMBA,			CPUID_EBX,  2, 0x80000020, 0 },
 	{ X86_FEATURE_BMEC,			CPUID_EBX,  3, 0x80000020, 0 },
 	{ X86_FEATURE_ABMC,			CPUID_EBX,  5, 0x80000020, 0 },
+	{ X86_FEATURE_SDCIAE,			CPUID_EBX,  6, 0x80000020, 0 },
 	{ X86_FEATURE_TSA_SQ_NO,		CPUID_ECX,  1, 0x80000021, 0 },
 	{ X86_FEATURE_TSA_L1_NO,		CPUID_ECX,  2, 0x80000021, 0 },
 	{ X86_FEATURE_AMD_WORKLOAD_CLASS,	CPUID_EAX, 22, 0x80000021, 0 },