linux-kernel - [PATCH v3 16/19] x86/sev: Avoid WARN() in early code

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Date: Mon, 29 Jan 2024 19:05:19 +0100
From: Ard Biesheuvel <ardb+git@...gle.com>
To: linux-kernel@...r.kernel.org
Cc: Ard Biesheuvel <ardb@...nel.org>, Kevin Loughlin <kevinloughlin@...gle.com>, 
	Tom Lendacky <thomas.lendacky@....com>, Dionna Glaze <dionnaglaze@...gle.com>, 
	Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>, 
	Dave Hansen <dave.hansen@...ux.intel.com>, Andy Lutomirski <luto@...nel.org>, 
	Arnd Bergmann <arnd@...db.de>, Nathan Chancellor <nathan@...nel.org>, 
	Nick Desaulniers <ndesaulniers@...gle.com>, Justin Stitt <justinstitt@...gle.com>, 
	Kees Cook <keescook@...omium.org>, Brian Gerst <brgerst@...il.com>, linux-arch@...r.kernel.org, 
	llvm@...ts.linux.dev
Subject: [PATCH v3 16/19] x86/sev: Avoid WARN() in early code

From: Ard Biesheuvel <ardb@...nel.org>

Drop uses of WARN() from code that is reachable from the early primary
boot path which executes via the initial 1:1 mapping before the kernel
page tables are populated. This is unsafe and mostly pointless, given
that printk() does not actually work yet at this point.

Signed-off-by: Ard Biesheuvel <ardb@...nel.org>
---
 arch/x86/kernel/sev.c | 13 ++++---------
 1 file changed, 4 insertions(+), 9 deletions(-)

diff --git a/arch/x86/kernel/sev.c b/arch/x86/kernel/sev.c
index 62981b463b76..94bf054bbde3 100644
--- a/arch/x86/kernel/sev.c
+++ b/arch/x86/kernel/sev.c
@@ -698,7 +698,7 @@ static void __pitext early_set_pages_state(unsigned long vaddr, unsigned long pa
 		if (op == SNP_PAGE_STATE_SHARED) {
 			/* Page validation must be rescinded before changing to shared */
 			ret = pvalidate(vaddr, RMP_PG_SIZE_4K, false);
-			if (WARN(ret, "Failed to validate address 0x%lx ret %d", paddr, ret))
+			if (ret)
 				goto e_term;
 		}
 
@@ -711,21 +711,16 @@ static void __pitext early_set_pages_state(unsigned long vaddr, unsigned long pa
 
 		val = sev_es_rd_ghcb_msr();
 
-		if (WARN(GHCB_RESP_CODE(val) != GHCB_MSR_PSC_RESP,
-			 "Wrong PSC response code: 0x%x\n",
-			 (unsigned int)GHCB_RESP_CODE(val)))
+		if (GHCB_RESP_CODE(val) != GHCB_MSR_PSC_RESP)
 			goto e_term;
 
-		if (WARN(GHCB_MSR_PSC_RESP_VAL(val),
-			 "Failed to change page state to '%s' paddr 0x%lx error 0x%llx\n",
-			 op == SNP_PAGE_STATE_PRIVATE ? "private" : "shared",
-			 paddr, GHCB_MSR_PSC_RESP_VAL(val)))
+		if (GHCB_MSR_PSC_RESP_VAL(val))
 			goto e_term;
 
 		if (op == SNP_PAGE_STATE_PRIVATE) {
 			/* Page validation must be performed after changing to private */
 			ret = pvalidate(vaddr, RMP_PG_SIZE_4K, true);
-			if (WARN(ret, "Failed to validate address 0x%lx ret %d", paddr, ret))
+			if (ret)
 				goto e_term;
 		}
 
-- 
2.43.0.429.g432eaa2c6b-goog