update kernel to 5.10.198

hc

2024-01-03 2f7c68cb55ecb7331f2381deb497c27155f32faf

 kernel/arch/x86/include/asm/debugreg.h
..
..
@@ -39,7 +39,20 @@
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 		asm("mov %%db6, %0" :"=r" (val));
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 		break;
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 	case 7:
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-		asm("mov %%db7, %0" :"=r" (val));
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+		/*
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+		 * Apply __FORCE_ORDER to DR7 reads to forbid re-ordering them
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+		 * with other code.
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+		 *
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+		 * This is needed because a DR7 access can cause a #VC exception
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+		 * when running under SEV-ES. Taking a #VC exception is not a
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+		 * safe thing to do just anywhere in the entry code and
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+		 * re-ordering might place the access into an unsafe location.
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+		 *
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+		 * This happened in the NMI handler, where the DR7 read was
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+		 * re-ordered to happen before the call to sev_es_ist_enter(),
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+		 * causing stack recursion.
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+		 */
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+		asm volatile("mov %%db7, %0" : "=r" (val) : __FORCE_ORDER);
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 		break;
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 	default:
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 		BUG();
..
..
@@ -66,7 +79,16 @@
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 		asm("mov %0, %%db6"	::"r" (value));
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 		break;
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 	case 7:
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-		asm("mov %0, %%db7"	::"r" (value));
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+		/*
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+		 * Apply __FORCE_ORDER to DR7 writes to forbid re-ordering them
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+		 * with other code.
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+		 *
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+		 * While is didn't happen with a DR7 write (see the DR7 read
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+		 * comment above which explains where it happened), add the
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+		 * __FORCE_ORDER here too to avoid similar problems in the
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+		 * future.
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+		 */
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+		asm volatile("mov %0, %%db7"	::"r" (value), __FORCE_ORDER);
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 		break;
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 	default:
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 		BUG();