6.12-stable review patch. If anyone has any objections, please let me know.
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From: Xin Li (Intel) xin@zytor.com
[ Upstream commit e5f1e8af9c9e151ecd665f6d2e36fb25fec3b110 ]
Upon a wakeup from S4, the restore kernel starts and initializes the FRED MSRs as needed from its perspective. It then loads a hibernation image, including the image kernel, and attempts to load image pages directly into their original page frames used before hibernation unless those frames are currently in use. Once all pages are moved to their original locations, it jumps to a "trampoline" page in the image kernel.
At this point, the image kernel takes control, but the FRED MSRs still contain values set by the restore kernel, which may differ from those set by the image kernel before hibernation. Therefore, the image kernel must ensure the FRED MSRs have the same values as before hibernation. Since these values depend only on the location of the kernel text and data, they can be recomputed from scratch.
Reported-by: Xi Pardee xi.pardee@intel.com Reported-by: Todd Brandt todd.e.brandt@intel.com 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 Signed-off-by: Ingo Molnar mingo@kernel.org Reviewed-by: Rafael J. Wysocki rafael.j.wysocki@intel.com Reviewed-by: H. Peter Anvin (Intel) hpa@zytor.com Cc: Andy Lutomirski luto@kernel.org Cc: Brian Gerst brgerst@gmail.com Cc: Juergen Gross jgross@suse.com Cc: Linus Torvalds torvalds@linux-foundation.org Link: https://lore.kernel.org/r/20250401075728.3626147-1-xin@zytor.com Signed-off-by: Sasha Levin sashal@kernel.org --- arch/x86/power/cpu.c | 14 ++++++++++++++ 1 file changed, 14 insertions(+)
diff --git a/arch/x86/power/cpu.c b/arch/x86/power/cpu.c index 63230ff8cf4f0..08e76a5ca1553 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 +232,19 @@ static void notrace __restore_processor_state(struct saved_context *ctxt) */ #ifdef CONFIG_X86_64 wrmsrl(MSR_GS_BASE, ctxt->kernelmode_gs_base); + + /* + * Reinitialize FRED to ensure the FRED MSRs contain the same values + * as before hibernation. + * + * Note, the setup of FRED RSPs requires access to percpu data + * structures. Therefore, FRED reinitialization can only occur after + * the percpu access pointer (i.e., MSR_GS_BASE) is restored. + */ + if (ctxt->cr4 & X86_CR4_FRED) { + cpu_init_fred_exceptions(); + cpu_init_fred_rsps(); + } #else loadsegment(fs, __KERNEL_PERCPU); #endif