From mboxrd@z Thu Jan 1 00:00:00 1970 From: Konrad Rzeszutek Wilk Subject: Re: [PATCH 1/4] x86/wakeup/sleep: Check whether the TSS GDT descriptor is empty before using it. Date: Thu, 18 Oct 2012 10:47:12 -0400 Message-ID: <20121018144709.GB19782@localhost.localdomain> References: <1350481786-4969-1-git-send-email-konrad.wilk@oracle.com> <1350481786-4969-2-git-send-email-konrad.wilk@oracle.com> <507F473D.1060700@zytor.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <507F473D.1060700@zytor.com> Sender: linux-acpi-owner@vger.kernel.org To: "H. Peter Anvin" Cc: linux-kernel@vger.kernel.org, xen-devel@lists.xensource.com, lenb@kernel.org, linux-acpi@vger.kernel.org, x86@kernel.org List-Id: xen-devel@lists.xenproject.org On Wed, Oct 17, 2012 at 05:03:09PM -0700, H. Peter Anvin wrote: > On 10/17/2012 06:49 AM, Konrad Rzeszutek Wilk wrote: > >We check the TSS descriptor before we try to dereference it. > >Also fix up the value to use the #defines. > > > >Signed-off-by: Konrad Rzeszutek Wilk > >--- > > arch/x86/power/cpu.c | 7 +++++-- > > 1 files changed, 5 insertions(+), 2 deletions(-) > > > >diff --git a/arch/x86/power/cpu.c b/arch/x86/power/cpu.c > >index 218cdb1..c17370e 100644 > >--- a/arch/x86/power/cpu.c > >+++ b/arch/x86/power/cpu.c > >@@ -133,7 +133,9 @@ static void fix_processor_context(void) > > { > > int cpu = smp_processor_id(); > > struct tss_struct *t = &per_cpu(init_tss, cpu); > >- > >+#ifdef CONFIG_X86_64 > >+ struct desc_struct *desc = get_cpu_gdt_table(cpu); > >+#endif > > set_tss_desc(cpu, t); /* > > * This just modifies memory; should not be > > * necessary. But... This is necessary, because > >@@ -142,7 +144,8 @@ static void fix_processor_context(void) > > */ > > > > #ifdef CONFIG_X86_64 > >- get_cpu_gdt_table(cpu)[GDT_ENTRY_TSS].type = 9; > >+ if (!desc_empty(&desc[GDT_ENTRY_TSS])) > >+ desc[GDT_ENTRY_TSS].type = DESC_TSS; > > > > syscall_init(); /* This sets MSR_*STAR and related */ > > #endif > > > > Why is this patch necessary? Presumably there is something further > down the line which depends on the TSS descriptor being empty, but > if so, what? I could not find it. This write has been in the code since the initial git history. Is the pre-git bitkeeper tree somewhere available? > > -hpa > > -- > H. Peter Anvin, Intel Open Source Technology Center > I work for Intel. I don't speak on their behalf. >