From: "H. Peter Anvin" <hpa@zytor.com>
To: Brian Gerst <brgerst@gmail.com>,
linux-kernel@vger.kernel.org, x86@kernel.org
Cc: David Woodhouse <dwmw2@infradead.org>,
Usama Arif <usama.arif@bytedance.com>,
Thomas Gleixner <tglx@linutronix.de>,
Borislav Petkov <bp@alien8.de>,
Peter Zijlstra <peterz@infradead.org>,
Andy Lutomirski <luto@kernel.org>, Ingo Molnar <mingo@kernel.org>
Subject: Re: [PATCH 4/6] x86/smpbppt: Remove early_gdt_descr on 64-bit
Date: Wed, 22 Feb 2023 22:49:26 -0800 [thread overview]
Message-ID: <47E3748A-47CB-4F83-9125-2570968C3280@zytor.com> (raw)
In-Reply-To: <20230222221301.245890-5-brgerst@gmail.com>
On February 22, 2023 2:12:59 PM PST, Brian Gerst <brgerst@gmail.com> wrote:
>Build the GDT descriptor on the stack instead.
>
>Signed-off-by: Brian Gerst <brgerst@gmail.com>
>---
> arch/x86/kernel/acpi/sleep.c | 2 --
> arch/x86/kernel/head_64.S | 19 +++++++------------
> 2 files changed, 7 insertions(+), 14 deletions(-)
>
>diff --git a/arch/x86/kernel/acpi/sleep.c b/arch/x86/kernel/acpi/sleep.c
>index 008fda8b1982..6538ddb55f28 100644
>--- a/arch/x86/kernel/acpi/sleep.c
>+++ b/arch/x86/kernel/acpi/sleep.c
>@@ -114,8 +114,6 @@ int x86_acpi_suspend_lowlevel(void)
> #else /* CONFIG_64BIT */
> #ifdef CONFIG_SMP
> current->thread.sp = (unsigned long)temp_stack + sizeof(temp_stack);
>- early_gdt_descr.address =
>- (unsigned long)get_cpu_gdt_rw(smp_processor_id());
> initial_gs = per_cpu_offset(smp_processor_id());
> /* Force the startup into boot mode */
> saved_smpboot_ctrl = xchg(&smpboot_control, 0);
>diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S
>index f7905ba4b992..0dd57d573a0e 100644
>--- a/arch/x86/kernel/head_64.S
>+++ b/arch/x86/kernel/head_64.S
>@@ -245,7 +245,7 @@ SYM_INNER_LABEL(secondary_startup_64_no_verify, SYM_L_GLOBAL)
> #ifdef CONFIG_SMP
> /*
> * Is this the boot CPU coming up? If so everything is available
>- * in initial_gs and early_gdt_descr.
>+ * in initial_gs.
> */
> movl smpboot_control(%rip), %edx
> testl $STARTUP_SECONDARY, %edx
>@@ -313,11 +313,6 @@ SYM_INNER_LABEL(secondary_startup_64_no_verify, SYM_L_GLOBAL)
> /* Save it for GS BASE setup */
> movq %rbx, initial_gs(%rip)
>
>- /* Calculate the GDT address */
>- movq $gdt_page, %rcx
>- addq %rbx, %rcx
>- movq %rcx, early_gdt_descr_base(%rip)
>-
> movq %rbx, %rdx
> #else
> xorl %edx, %edx
>@@ -339,7 +334,12 @@ SYM_INNER_LABEL(secondary_startup_64_no_verify, SYM_L_GLOBAL)
> * addresses where we're currently running on. We have to do that here
> * because in 32bit we couldn't load a 64bit linear address.
> */
>- lgdt early_gdt_descr(%rip)
>+ subq $16, %rsp
>+ movw $(GDT_SIZE-1), (%rsp)
>+ leaq gdt_page(%rdx), %rax
>+ movq %rax, 2(%rsp)
>+ lgdt (%rsp)
>+ addq $16, %rsp
>
> /* set up data segments */
> xorl %eax,%eax
>@@ -754,11 +754,6 @@ SYM_DATA_END(level1_fixmap_pgt)
>
> .data
> .align 16
>-
>-SYM_DATA(early_gdt_descr, .word GDT_ENTRIES*8-1)
>-SYM_DATA_LOCAL(early_gdt_descr_base, .quad INIT_PER_CPU_VAR(gdt_page))
>-
>- .align 16
> SYM_DATA(smpboot_control, .long 0)
>
> .align 16
This is known to break at least some hypervisors, probably old by now, but...
next prev parent reply other threads:[~2023-02-23 6:50 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-02-22 22:12 [PATCH 0/6] x86-64: Remove global variables from boot Brian Gerst
2023-02-22 22:12 ` [PATCH 1/6] x86/smpboot: Use CPU number instead of APIC ID for single CPU startup Brian Gerst
2023-02-22 22:12 ` [PATCH 2/6] x86/smpboot: Use current_task to get idle thread Brian Gerst
2023-02-22 22:12 ` [PATCH 3/6] x86/smpboot: Remove initial_stack on 64-bit Brian Gerst
2023-02-23 8:05 ` David Woodhouse
2023-02-23 8:27 ` David Woodhouse
2023-02-22 22:12 ` [PATCH 4/6] x86/smpbppt: Remove early_gdt_descr " Brian Gerst
2023-02-23 6:49 ` H. Peter Anvin [this message]
2023-02-23 12:10 ` Brian Gerst
2023-02-22 22:13 ` [PATCH 5/6] x86/smpboot: Remove initial_gs Brian Gerst
2023-02-22 22:13 ` [PATCH 6/6] x86/smpboot: Simplify boot CPU setup Brian Gerst
2023-02-23 12:36 ` David Woodhouse
2023-02-23 13:44 ` [PATCH 0/6] x86-64: Remove global variables from boot David Woodhouse
2023-02-23 14:24 ` Brian Gerst
2023-02-23 19:14 ` [External] " Usama Arif
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