From: Josh Poimboeuf <jpoimboe@kernel.org>
To: x86@kernel.org
Cc: linux-kernel@vger.kernel.org, amit@kernel.org,
kvm@vger.kernel.org, amit.shah@amd.com, thomas.lendacky@amd.com,
bp@alien8.de, tglx@linutronix.de, peterz@infradead.org,
pawan.kumar.gupta@linux.intel.com, corbet@lwn.net,
mingo@redhat.com, dave.hansen@linux.intel.com, hpa@zytor.com,
seanjc@google.com, pbonzini@redhat.com,
daniel.sneddon@linux.intel.com, kai.huang@intel.com,
sandipan.das@amd.com, boris.ostrovsky@oracle.com,
Babu.Moger@amd.com, david.kaplan@amd.com, dwmw@amazon.co.uk,
andrew.cooper3@citrix.comm, nik.borisov@suse.com
Subject: [PATCH v4 2/6] x86/bugs: Use SBPB in write_ibpb() if applicable
Date: Tue, 8 Apr 2025 14:47:31 -0700 [thread overview]
Message-ID: <17c5dcd14b29199b75199d67ff7758de9d9a4928.1744148254.git.jpoimboe@kernel.org> (raw)
In-Reply-To: <cover.1744148254.git.jpoimboe@kernel.org>
write_ibpb() does IBPB, which (among other things) flushes branch type
predictions on AMD. If the CPU has SRSO_NO, or if the SRSO mitigation
has been disabled, branch type flushing isn't needed, in which case the
lighter-weight SBPB can be used.
The 'x86_pred_cmd' variable already keeps track of whether IBPB or SBPB
should be used. Use that instead of hardcoding IBPB.
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
---
arch/x86/entry/entry.S | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/x86/entry/entry.S b/arch/x86/entry/entry.S
index cabe65ac8379..175958b02f2b 100644
--- a/arch/x86/entry/entry.S
+++ b/arch/x86/entry/entry.S
@@ -21,7 +21,7 @@
SYM_FUNC_START(write_ibpb)
ANNOTATE_NOENDBR
movl $MSR_IA32_PRED_CMD, %ecx
- movl $PRED_CMD_IBPB, %eax
+ movl _ASM_RIP(x86_pred_cmd), %eax
xorl %edx, %edx
wrmsr
--
2.49.0
next prev parent reply other threads:[~2025-04-08 21:48 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-04-08 21:47 [PATCH v4 0/6] x86/bugs: RSB mitigation fixes and documentation Josh Poimboeuf
2025-04-08 21:47 ` [PATCH v4 1/6] x86/bugs: Rename entry_ibpb() to write_ibpb() Josh Poimboeuf
2025-04-09 11:44 ` [tip: x86/urgent] " tip-bot2 for Josh Poimboeuf
2025-04-08 21:47 ` Josh Poimboeuf [this message]
2025-04-09 11:44 ` [tip: x86/urgent] x86/bugs: Use SBPB in write_ibpb() if applicable tip-bot2 for Josh Poimboeuf
2025-04-08 21:47 ` [PATCH v4 3/6] x86/bugs: Fix RSB clearing in indirect_branch_prediction_barrier() Josh Poimboeuf
2025-04-09 11:44 ` [tip: x86/urgent] " tip-bot2 for Josh Poimboeuf
2025-04-08 21:47 ` [PATCH v4 4/6] x86/bugs: Don't fill RSB on VMEXIT with eIBRS+retpoline Josh Poimboeuf
2025-04-09 11:44 ` [tip: x86/urgent] " tip-bot2 for Josh Poimboeuf
2025-04-08 21:47 ` [PATCH v4 5/6] x86/bugs: Don't fill RSB on context switch with eIBRS Josh Poimboeuf
2025-04-09 11:44 ` [tip: x86/urgent] " tip-bot2 for Josh Poimboeuf
2025-04-08 21:47 ` [PATCH v4 6/6] x86/bugs: Add RSB mitigation document Josh Poimboeuf
2025-04-09 11:44 ` [tip: x86/urgent] " tip-bot2 for Josh Poimboeuf
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=17c5dcd14b29199b75199d67ff7758de9d9a4928.1744148254.git.jpoimboe@kernel.org \
--to=jpoimboe@kernel.org \
--cc=Babu.Moger@amd.com \
--cc=amit.shah@amd.com \
--cc=amit@kernel.org \
--cc=andrew.cooper3@citrix.comm \
--cc=boris.ostrovsky@oracle.com \
--cc=bp@alien8.de \
--cc=corbet@lwn.net \
--cc=daniel.sneddon@linux.intel.com \
--cc=dave.hansen@linux.intel.com \
--cc=david.kaplan@amd.com \
--cc=dwmw@amazon.co.uk \
--cc=hpa@zytor.com \
--cc=kai.huang@intel.com \
--cc=kvm@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=mingo@redhat.com \
--cc=nik.borisov@suse.com \
--cc=pawan.kumar.gupta@linux.intel.com \
--cc=pbonzini@redhat.com \
--cc=peterz@infradead.org \
--cc=sandipan.das@amd.com \
--cc=seanjc@google.com \
--cc=tglx@linutronix.de \
--cc=thomas.lendacky@amd.com \
--cc=x86@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox
all inboxes | Powered by JetHome®