[PATCH 21/36] x86/tdx: Remove TDX_HCALL_ISSUE_STI
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- To: peterz@xxxxxxxxxxxxx
- Subject: [PATCH 21/36] x86/tdx: Remove TDX_HCALL_ISSUE_STI
- From: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
- Date: Wed, 08 Jun 2022 16:27:44 +0200
- Cc: rth@xxxxxxxxxxxxxxx, ink@xxxxxxxxxxxxxxxxxxxx, mattst88@xxxxxxxxx, vgupta@xxxxxxxxxx, linux@xxxxxxxxxxxxxxx, ulli.kroll@xxxxxxxxxxxxxx, linus.walleij@xxxxxxxxxx, shawnguo@xxxxxxxxxx, Sascha Hauer <s.hauer@xxxxxxxxxxxxxx>, kernel@xxxxxxxxxxxxxx, festevam@xxxxxxxxx, linux-imx@xxxxxxx, tony@xxxxxxxxxxx, khilman@xxxxxxxxxx, catalin.marinas@xxxxxxx, will@xxxxxxxxxx, guoren@xxxxxxxxxx, bcain@xxxxxxxxxxx, chenhuacai@xxxxxxxxxx, kernel@xxxxxxxxxx, geert@xxxxxxxxxxxxxx, sammy@xxxxxxxxx, monstr@xxxxxxxxx, tsbogend@xxxxxxxxxxxxxxxx, dinguyen@xxxxxxxxxx, jonas@xxxxxxxxxxxx, stefan.kristiansson@xxxxxxxxxxxxx, shorne@xxxxxxxxx, James.Bottomley@xxxxxxxxxxxxxxxxxxxxx, deller@xxxxxx, mpe@xxxxxxxxxxxxxx, benh@xxxxxxxxxxxxxxxxxxx, paulus@xxxxxxxxx, paul.walmsley@xxxxxxxxxx, palmer@xxxxxxxxxxx, aou@xxxxxxxxxxxxxxxxx, hca@xxxxxxxxxxxxx, gor@xxxxxxxxxxxxx, agordeev@xxxxxxxxxxxxx, borntraeger@xxxxxxxxxxxxx, svens@xxxxxxxxxxxxx, ysato@xxxxxxxxxxxxx, dalias@xxxxxxxx, davem@xxxxxxxxxxxxx, richard@xxxxxx, anton.ivanov@xxxxxxxxxxxxxxxxxx, johannes@xxxxxxxxxxxxxxxx, tglx@xxxxxxxxxxxxx, mingo@xxxxxxxxxx, bp@xxxxxxxxx, dave.hansen@xxxxxxxxxxxxxxx, x86@xxxxxxxxxx, hpa@xxxxxxxxx, acme@xxxxxxxxxx, mark.rutland@xxxxxxx, alexander.shishkin@xxxxxxxxxxxxxxx, jolsa@xxxxxxxxxx, namhyung@xxxxxxxxxx, jgross@xxxxxxxx, srivatsa@xxxxxxxxxxxxx, amakhalov@xxxxxxxxxx, pv-drivers@xxxxxxxxxx, boris.ostrovsky@xxxxxxxxxx, chris@xxxxxxxxxx, jcmvbkbc@xxxxxxxxx, rafael@xxxxxxxxxx, lenb@xxxxxxxxxx, pavel@xxxxxx, gregkh@xxxxxxxxxxxxxxxxxxx, mturquette@xxxxxxxxxxxx, sboyd@xxxxxxxxxx, daniel.lezcano@xxxxxxxxxx, lpieralisi@xxxxxxxxxx, sudeep.holla@xxxxxxx, agross@xxxxxxxxxx, bjorn.andersson@xxxxxxxxxx, anup@xxxxxxxxxxxxxx, thierry.reding@xxxxxxxxx, jonathanh@xxxxxxxxxx, jacob.jun.pan@xxxxxxxxxxxxxxx, Arnd Bergmann <arnd@xxxxxxxx>, yury.norov@xxxxxxxxx, andriy.shevchenko@xxxxxxxxxxxxxxx, linux@xxxxxxxxxxxxxxxxxx, rostedt@xxxxxxxxxxx, pmladek@xxxxxxxx, senozhatsky@xxxxxxxxxxxx, john.ogness@xxxxxxxxxxxxx, paulmck@xxxxxxxxxx, frederic@xxxxxxxxxx, quic_neeraju@xxxxxxxxxxx, josh@xxxxxxxxxxxxxxxx, mathieu.desnoyers@xxxxxxxxxxxx, jiangshanlai@xxxxxxxxx, joel@xxxxxxxxxxxxxxxxx, juri.lelli@xxxxxxxxxx, vincent.guittot@xxxxxxxxxx, dietmar.eggemann@xxxxxxx, bsegall@xxxxxxxxxx, mgorman@xxxxxxx, bristot@xxxxxxxxxx, vschneid@xxxxxxxxxx, jpoimboe@xxxxxxxxxx, linux-alpha@xxxxxxxxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx, linux-snps-arc@xxxxxxxxxxxxxxxxxxx, linux-arm-kernel@xxxxxxxxxxxxxxxxxxx, linux-omap@xxxxxxxxxxxxxxx, linux-csky@xxxxxxxxxxxxxxx, linux-hexagon@xxxxxxxxxxxxxxx, linux-ia64@xxxxxxxxxxxxxxx, linux-m68k@xxxxxxxxxxxxxxx, linux-mips@xxxxxxxxxxxxxxx, openrisc@xxxxxxxxxxxxxxxxxxxx, linux-parisc@xxxxxxxxxxxxxxx, linuxppc-dev@xxxxxxxxxxxxxxxx, linux-riscv@xxxxxxxxxxxxxxxxxxx, linux-s390@xxxxxxxxxxxxxxx, linux-sh@xxxxxxxxxxxxxxx, sparclinux@xxxxxxxxxxxxxxx, linux-um@xxxxxxxxxxxxxxxxxxx, linux-perf-users@xxxxxxxxxxxxxxx, virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx, xen-devel@xxxxxxxxxxxxxxxxxxxx, linux-xtensa@xxxxxxxxxxxxxxxx, linux-acpi@xxxxxxxxxxxxxxx, linux-pm@xxxxxxxxxxxxxxx, linux-clk@xxxxxxxxxxxxxxx, linux-arm-msm@xxxxxxxxxxxxxxx, linux-tegra@xxxxxxxxxxxxxxx, linux-arch@xxxxxxxxxxxxxxx, rcu@xxxxxxxxxxxxxxx, Isaku Yamahata <isaku.yamahata@xxxxxxxxx>, kirill.shutemov@xxxxxxxxxxxxxxx
- References: <20220608142723.103523089@infradead.org>
- User-agent: quilt/0.66
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 <isaku.yamahata@xxxxxxxxx>
Cc: kirill.shutemov@xxxxxxxxxxxxxxx
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
---
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 "
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