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Message-Id: <20220128202905.2274672-11-fenghua.yu@intel.com>
Date: Fri, 28 Jan 2022 12:29:04 -0800
From: Fenghua Yu <fenghua.yu@...el.com>
To: "Thomas Gleixner" <tglx@...utronix.de>,
"Dave Hansen" <dave.hansen@...ux.intel.com>,
"Ingo Molnar" <mingo@...hat.com>, "Borislav Petkov" <bp@...en8.de>,
"Peter Zijlstra" <peterz@...radead.org>,
"Andy Lutomirski" <luto@...nel.org>,
"Tony Luck" <tony.luck@...el.com>,
"Lu Baolu" <baolu.lu@...ux.intel.com>,
"Joerg Roedel" <joro@...tes.org>,
Josh Poimboeuf <jpoimboe@...hat.com>,
"Jacob Pan" <jacob.jun.pan@...ux.intel.com>,
"Ashok Raj" <ashok.raj@...el.com>,
"Ravi V Shankar" <ravi.v.shankar@...el.com>
Cc: iommu@...ts.linux-foundation.org, "x86" <x86@...nel.org>,
"linux-kernel" <linux-kernel@...r.kernel.org>,
Fenghua Yu <fenghua.yu@...el.com>
Subject: [PATCH v3 10/11] tools/objtool: Check for use of the ENQCMD instruction in the kernel
The ENQCMD implicitly accesses the PASID_MSR to fill in the pasid field
of the descriptor being submitted to an accelerator. But there is no
precise (and stable across kernel changes) point at which the PASID_MSR
is updated from the value for one task to the next.
Kernel code that uses accelerators must always use the ENQCMDS instruction
which does not access the PASID_MSR.
Check for use of the ENQCMD instruction in the kernel and warn on its
usage.
Signed-off-by: Fenghua Yu <fenghua.yu@...el.com>
Reviewed-by: Tony Luck <tony.luck@...el.com>
Acked-by: Josh Poimboeuf <jpoimboe@...hat.com>
---
v3:
- Add Acked-by: Josh Poimboeuf <jpoimboe@...hat.com>
v2:
- Simplify handling ENQCMD (PeterZ and Josh)
tools/objtool/arch/x86/decode.c | 11 ++++++++++-
1 file changed, 10 insertions(+), 1 deletion(-)
diff --git a/tools/objtool/arch/x86/decode.c b/tools/objtool/arch/x86/decode.c
index c10ef78df050..479e769ca324 100644
--- a/tools/objtool/arch/x86/decode.c
+++ b/tools/objtool/arch/x86/decode.c
@@ -112,7 +112,7 @@ int arch_decode_instruction(struct objtool_file *file, const struct section *sec
const struct elf *elf = file->elf;
struct insn insn;
int x86_64, ret;
- unsigned char op1, op2,
+ unsigned char op1, op2, op3,
rex = 0, rex_b = 0, rex_r = 0, rex_w = 0, rex_x = 0,
modrm = 0, modrm_mod = 0, modrm_rm = 0, modrm_reg = 0,
sib = 0, /* sib_scale = 0, */ sib_index = 0, sib_base = 0;
@@ -139,6 +139,7 @@ int arch_decode_instruction(struct objtool_file *file, const struct section *sec
op1 = insn.opcode.bytes[0];
op2 = insn.opcode.bytes[1];
+ op3 = insn.opcode.bytes[2];
if (insn.rex_prefix.nbytes) {
rex = insn.rex_prefix.bytes[0];
@@ -491,6 +492,14 @@ int arch_decode_instruction(struct objtool_file *file, const struct section *sec
/* nopl/nopw */
*type = INSN_NOP;
+ } else if (op2 == 0x38 && op3 == 0xf8) {
+ if (insn.prefixes.nbytes == 1 &&
+ insn.prefixes.bytes[0] == 0xf2) {
+ /* ENQCMD cannot be used in the kernel. */
+ WARN("ENQCMD instruction at %s:%lx", sec->name,
+ offset);
+ }
+
} else if (op2 == 0xa0 || op2 == 0xa8) {
/* push fs/gs */
--
2.35.0
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