linux-kernel - [RFC PATCH v6.10 1/4] x86/sev: Avoid WARN()s in early boot code

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Date: Thu,  7 Mar 2024 15:30:29 +0100
From: Ard Biesheuvel <ardb+git@...gle.com>
To: linux-kernel@...gle.com
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>, Kees Cook <keescook@...omium.org>, Brian Gerst <brgerst@...il.com>, 
	linux-kernel@...r.kernel.org
Subject: [RFC PATCH v6.10 1/4] x86/sev: Avoid WARN()s in early boot code

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

Using WARN() before the kernel is even mapped is unlikely to do anything
useful: the string literals are passed using their kernel virtual
addresses which are not even mapped yet. But even if they were, calling
into the printk machinery from the early 1:1 mapped code is not going to
get very far.

So drop the WARN()s entirely.

Signed-off-by: Ard Biesheuvel <ardb@...nel.org>
---
 arch/x86/kernel/sev.c | 15 +++++----------
 1 file changed, 5 insertions(+), 10 deletions(-)

diff --git a/arch/x86/kernel/sev.c b/arch/x86/kernel/sev.c
index 33c14aa1f06c..fc1b7b331815 100644
--- a/arch/x86/kernel/sev.c
+++ b/arch/x86/kernel/sev.c
@@ -700,7 +700,7 @@ early_set_pages_state(unsigned long vaddr, unsigned long paddr,
 		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 			/* Page validation must be rescinded before changing to shared */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;
 		}
 
@@ -713,21 +713,16 @@ early_set_pages_state(unsigned long vaddr, unsigned long paddr,
 
 		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;
 		}
 
@@ -760,7 +755,7 @@ void __head early_snp_set_memory_private(unsigned long vaddr, unsigned long padd
 	early_set_pages_state(vaddr, paddr, npages, SNP_PAGE_STATE_PRIVATE);
 }
 
-void __init early_snp_set_memory_shared(unsigned long vaddr, unsigned long paddr,
+void __head early_snp_set_memory_shared(unsigned long vaddr, unsigned long paddr,
 					unsigned long npages)
 {
 	/*
-- 
2.44.0.278.ge034bb2e1d-goog