During an S4 resume, the system first performs a cold power-on. The kernel image is initially loaded to a random linear address, and the FRED MSRs are initialized. Subsequently, the S4 image is loaded, and the kernel image is relocated to its original address from before the S4 suspend. Due to changes in the kernel text and data mappings, the FRED MSRs must be reinitialized.
Reported-by: Xi Pardee xi.pardee@intel.com Reported-and-Tested-by: Todd Brandt todd.e.brandt@intel.com Suggested-by: H. Peter Anvin (Intel) hpa@zytor.com Signed-off-by: Xin Li (Intel) xin@zytor.com Cc: stable@kernel.org # 6.9+ --- arch/x86/power/cpu.c | 16 ++++++++++++++++ 1 file changed, 16 insertions(+)
diff --git a/arch/x86/power/cpu.c b/arch/x86/power/cpu.c index 63230ff8cf4f..ef3c152c319c 100644 --- a/arch/x86/power/cpu.c +++ b/arch/x86/power/cpu.c @@ -27,6 +27,7 @@ #include <asm/mmu_context.h> #include <asm/cpu_device_id.h> #include <asm/microcode.h> +#include <asm/fred.h>
#ifdef CONFIG_X86_32 __visible unsigned long saved_context_ebx; @@ -231,6 +232,21 @@ static void notrace __restore_processor_state(struct saved_context *ctxt) */ #ifdef CONFIG_X86_64 wrmsrl(MSR_GS_BASE, ctxt->kernelmode_gs_base); + + /* + * Restore FRED configs. + * + * FRED configs are completely derived from current kernel text and + * data mappings, thus nothing needs to be saved and restored. + * + * As such, simply re-initialize FRED to restore FRED configs. + * + * Note, FRED RSPs setup needs to access percpu data structures. + */ + if (ctxt->cr4 & X86_CR4_FRED) { + cpu_init_fred_exceptions(); + cpu_init_fred_rsps(); + } #else loadsegment(fs, __KERNEL_PERCPU); #endif