[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [PATCH v12 19/37] x86/fred: Update MSR_IA32_FRED_RSP0 during task switch
On Mon, Oct 02, 2023 at 11:24:40PM -0700, Xin Li wrote: > From: "H. Peter Anvin (Intel)" <hpa@xxxxxxxxx> > > MSR_IA32_FRED_RSP0 is used during ring 3 event delivery, and needs to > be updated to point to the top of next task stack during task switch. > > Signed-off-by: H. Peter Anvin (Intel) <hpa@xxxxxxxxx> > Tested-by: Shan Kang <shan.kang@xxxxxxxxx> > Signed-off-by: Xin Li <xin3.li@xxxxxxxxx> > --- > arch/x86/include/asm/switch_to.h | 8 ++++++-- > 1 file changed, 6 insertions(+), 2 deletions(-) > > diff --git a/arch/x86/include/asm/switch_to.h > b/arch/x86/include/asm/switch_to.h > index f42dbf17f52b..c3bd0c0758c9 100644 > --- a/arch/x86/include/asm/switch_to.h > +++ b/arch/x86/include/asm/switch_to.h > @@ -70,9 +70,13 @@ static inline void update_task_stack(struct task_struct > *task) > #ifdef CONFIG_X86_32 > this_cpu_write(cpu_tss_rw.x86_tss.sp1, task->thread.sp0); > #else > - /* Xen PV enters the kernel on the thread stack. */ > - if (cpu_feature_enabled(X86_FEATURE_XENPV)) > + if (cpu_feature_enabled(X86_FEATURE_FRED)) { > + /* WRMSRNS is a baseline feature for FRED. */ > + wrmsrns(MSR_IA32_FRED_RSP0, (unsigned > long)task_stack_page(task) + THREAD_SIZE); If this non-serializing write happens now and, AFAICT, the CR3 write during the task switch has already happened in switch_mm* earlier, what is the serialization point that's going to make sure that write is committed before the new task starts executing? Thx. -- Regards/Gruss, Boris. https://people.kernel.org/tglx/notes-about-netiquette
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