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([172.25.112.68]) by orsmga001.jf.intel.com with ESMTP; 13 Sep 2023 22:17:47 -0700 From: Xin Li To: linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-edac@vger.kernel.org, linux-hyperv@vger.kernel.org, kvm@vger.kernel.org, xen-devel@lists.xenproject.org Cc: tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com, luto@kernel.org, pbonzini@redhat.com, seanjc@google.com, peterz@infradead.org, jgross@suse.com, ravi.v.shankar@intel.com, mhiramat@kernel.org, andrew.cooper3@citrix.com, jiangshanlai@gmail.com Subject: [PATCH v10 36/38] x86/fred: Add fred_syscall_init() Date: Wed, 13 Sep 2023 21:48:03 -0700 Message-Id: <20230914044805.301390-37-xin3.li@intel.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20230914044805.301390-1-xin3.li@intel.com> References: <20230914044805.301390-1-xin3.li@intel.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-Greylist: Sender passed SPF test, not delayed by milter-greylist-4.6.4 (fry.vger.email [0.0.0.0]); Wed, 13 Sep 2023 22:21:32 -0700 (PDT) X-Spam-Status: No, score=-0.9 required=5.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=unavailable autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on fry.vger.email X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: 1777006530873395439 X-GMAIL-MSGID: 1777006530873395439 From: "H. Peter Anvin (Intel)" Add a syscall initialization function fred_syscall_init() for FRED, and this is really just to skip setting up SYSCALL/SYSENTER related MSRs, e.g., MSR_LSTAR and invalidate SYSENTER configurations, because FRED uses the ring 3 FRED entrypoint for SYSCALL and SYSENTER, and ERETU is the only legit instruction to return to ring 3 per FRED spec 5.0. Signed-off-by: H. Peter Anvin (Intel) Tested-by: Shan Kang Signed-off-by: Xin Li --- arch/x86/kernel/cpu/common.c | 17 +++++++++++++++++ 1 file changed, 17 insertions(+) diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c index d960b7276008..4cb36e241c9a 100644 --- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c @@ -2105,6 +2105,23 @@ static inline void idt_syscall_init(void) X86_EFLAGS_AC|X86_EFLAGS_ID); } +static inline void fred_syscall_init(void) +{ + /* + * Per FRED spec 5.0, FRED uses the ring 3 FRED entrypoint for SYSCALL + * and SYSENTER, and ERETU is the only legit instruction to return to + * ring 3, as a result there is _no_ need to setup the SYSCALL and + * SYSENTER MSRs. + * + * Note, both sysexit and sysret cause #UD when FRED is enabled. + */ + wrmsrl(MSR_LSTAR, 0ULL); + wrmsrl_cstar(0ULL); + wrmsrl_safe(MSR_IA32_SYSENTER_CS, (u64)GDT_ENTRY_INVALID_SEG); + wrmsrl_safe(MSR_IA32_SYSENTER_ESP, 0ULL); + wrmsrl_safe(MSR_IA32_SYSENTER_EIP, 0ULL); +} + /* May not be marked __init: used by software suspend */ void syscall_init(void) {