From mboxrd@z Thu Jan 1 00:00:00 1970 From: Peter Zijlstra Subject: [PATCH 21/36] x86/tdx: Remove TDX_HCALL_ISSUE_STI Date: Wed, 08 Jun 2022 16:27:44 +0200 Message-ID: <20220608144517.251109029@infradead.org> References: <20220608142723.103523089@infradead.org> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=desiato.20200630; h=Content-Type:MIME-Version:References: Subject:Cc:To:From:Date:Message-ID:Sender:Reply-To:Content-Transfer-Encoding: Content-ID:Content-Description:In-Reply-To; bh=n+8kbD5k3joQL4tu1DQuka314sY5HtbiPc/MGM3uXCw=; b=CFsFgByJSeY2PmftE59lIwd61A fjJ72jju0l9GwBYm1tDQavNTQt1uwtfxtPtqec7K6IBFRtI8mUyMjSb23xu2nggDLQ3Izti62YLZ9 81i/g9DPcf892kC/BAGwIehJW/W7Fewyul66uCAJh+Bsk0BWV05Jio2VzipiczXpOVQR7AS6M8em5 wh3T1DJLe1ciqy+OR6gyRoeQARA3peLCGum9kfZYaXxBeujZ3coueZc7Rw5XccGKhOx8fJer5LVm7 DK6L3i+rJEhIKvEmmEfkmunPBAh5TavkMzTbRzPaMqLIGOwpl+o4n2Ge2dXsInCxEuWYARNglpkyB ylWDIb/Q==; List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: virtualization-bounces@lists.linux-foundation.org Sender: "Virtualization" To: peterz@infradead.org Cc: juri.lelli@redhat.com, rafael@kernel.org, benh@kernel.crashing.org, linus.walleij@linaro.org, bsegall@google.com, guoren@kernel.org, pavel@ucw.cz, agordeev@linux.ibm.com, linux-arch@vger.kernel.org, vincent.guittot@linaro.org, mpe@ellerman.id.au, chenhuacai@kernel.org, linux-acpi@vger.kernel.org, agross@kernel.org, geert@linux-m68k.org, linux-imx@nxp.com, catalin.marinas@arm.com, xen-devel@lists.xenproject.org, mattst88@gmail.com, mturquette@baylibre.com, sammy@sammy.net, pmladek@suse.com, linux-pm@vger.kernel.org, jiangshanlai@gmail.com, Sascha Hauer , linux-um@lists.infradead.org, acme@kernel.org, tglx@linutronix.de, linux-omap@vger.kernel.org, dietmar.eggemann@arm.com, rth@twiddle.net, gregkh@linuxfoundation.org, linux-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org, senozhatsky@chromium.org, svens@linux.ibm.com, jolsa@kernel.org, paul Now that arch_cpu_idle() is expected to return with IRQs disabled, avoid the useless STI/CLI dance. Per the specs this is supposed to work, but nobody has yet relied up this behaviour so broken implementations are possible. Cc: Isaku Yamahata Cc: kirill.shutemov@linux.intel.com Signed-off-by: Peter Zijlstra (Intel) --- arch/x86/coco/tdx/tdcall.S | 13 ------------- arch/x86/coco/tdx/tdx.c | 23 ++++------------------- arch/x86/include/asm/shared/tdx.h | 1 - 3 files changed, 4 insertions(+), 33 deletions(-) --- a/arch/x86/coco/tdx/tdcall.S +++ b/arch/x86/coco/tdx/tdcall.S @@ -139,19 +139,6 @@ SYM_FUNC_START(__tdx_hypercall) movl $TDVMCALL_EXPOSE_REGS_MASK, %ecx - /* - * For the idle loop STI needs to be called directly before the TDCALL - * that enters idle (EXIT_REASON_HLT case). STI instruction enables - * interrupts only one instruction later. If there is a window between - * STI and the instruction that emulates the HALT state, there is a - * chance for interrupts to happen in this window, which can delay the - * HLT operation indefinitely. Since this is the not the desired - * result, conditionally call STI before TDCALL. - */ - testq $TDX_HCALL_ISSUE_STI, %rsi - jz .Lskip_sti - sti -.Lskip_sti: tdcall /* --- a/arch/x86/coco/tdx/tdx.c +++ b/arch/x86/coco/tdx/tdx.c @@ -124,7 +124,7 @@ static u64 get_cc_mask(void) return BIT_ULL(gpa_width - 1); } -static u64 __cpuidle __halt(const bool irq_disabled, const bool do_sti) +static u64 __cpuidle __halt(const bool irq_disabled) { struct tdx_hypercall_args args = { .r10 = TDX_HYPERCALL_STANDARD, @@ -144,20 +144,14 @@ static u64 __cpuidle __halt(const bool i * can keep the vCPU in virtual HLT, even if an IRQ is * pending, without hanging/breaking the guest. */ - return __tdx_hypercall(&args, do_sti ? TDX_HCALL_ISSUE_STI : 0); + return __tdx_hypercall(&args, 0); } static bool handle_halt(void) { - /* - * Since non safe halt is mainly used in CPU offlining - * and the guest will always stay in the halt state, don't - * call the STI instruction (set do_sti as false). - */ const bool irq_disabled = irqs_disabled(); - const bool do_sti = false; - if (__halt(irq_disabled, do_sti)) + if (__halt(irq_disabled)) return false; return true; @@ -165,22 +159,13 @@ static bool handle_halt(void) void __cpuidle tdx_safe_halt(void) { - /* - * For do_sti=true case, __tdx_hypercall() function enables - * interrupts using the STI instruction before the TDCALL. So - * set irq_disabled as false. - */ const bool irq_disabled = false; - const bool do_sti = true; /* * Use WARN_ONCE() to report the failure. */ - if (__halt(irq_disabled, do_sti)) + if (__halt(irq_disabled)) WARN_ONCE(1, "HLT instruction emulation failed\n"); - - /* XXX I can't make sense of what @do_sti actually does */ - raw_local_irq_disable(); } static bool read_msr(struct pt_regs *regs) --- a/arch/x86/include/asm/shared/tdx.h +++ b/arch/x86/include/asm/shared/tdx.h @@ -8,7 +8,6 @@ #define TDX_HYPERCALL_STANDARD 0 #define TDX_HCALL_HAS_OUTPUT BIT(0) -#define TDX_HCALL_ISSUE_STI BIT(1) #define TDX_CPUID_LEAF_ID 0x21 #define TDX_IDENT "IntelTDX "