Thread (183 messages) 183 messages, 11 authors, 2022-01-29

Re: [PATCH v8 09/40] x86/compressed: Add helper for validating pages in the decompression stage

From: Borislav Petkov <bp@alien8.de>
Date: 2021-12-21 13:01:34
Also in: linux-coco, linux-efi, lkml, platform-driver-x86

On Fri, Dec 10, 2021 at 09:43:01AM -0600, Brijesh Singh wrote:
quoted hunk ↗ jump to hunk
diff --git a/arch/x86/boot/compressed/ident_map_64.c b/arch/x86/boot/compressed/ident_map_64.c
index f7213d0943b8..ef77453cc629 100644
--- a/arch/x86/boot/compressed/ident_map_64.c
+++ b/arch/x86/boot/compressed/ident_map_64.c
@@ -275,15 +275,31 @@ static int set_clr_page_flags(struct x86_mapping_info *info,
 	 * Changing encryption attributes of a page requires to flush it from
 	 * the caches.
 	 */
-	if ((set | clr) & _PAGE_ENC)
+	if ((set | clr) & _PAGE_ENC) {
 		clflush_page(address);
 
+		/*
+		 * If the encryption attribute is being cleared, then change
+		 * the page state to shared in the RMP table.
+		 */
+		if (clr)
+			snp_set_page_shared(pte_pfn(*ptep) << PAGE_SHIFT);
You forgot to change that one.
+	}
+
 	/* Update PTE */
 	pte = *ptep;
 	pte = pte_set_flags(pte, set);
 	pte = pte_clear_flags(pte, clr);
 	set_pte(ptep, pte);
 
+	/*
+	 * If the encryption attribute is being set, then change the page state to
+	 * private in the RMP entry. The page state must be done after the PTE
                                                   ^
                                                 change

Geez, tell me, why should I be even bothering to review stuff if I have
to go look at the previous review I did and find that you haven't really
addressed it?!
quoted hunk ↗ jump to hunk
diff --git a/arch/x86/include/asm/sev-common.h b/arch/x86/include/asm/sev-common.h
index 7ac5842e32b6..a2f956cfafba 100644
--- a/arch/x86/include/asm/sev-common.h
+++ b/arch/x86/include/asm/sev-common.h
@@ -57,6 +57,32 @@
 #define GHCB_MSR_AP_RESET_HOLD_REQ	0x006
 #define GHCB_MSR_AP_RESET_HOLD_RESP	0x007
 
+/*
+ * SNP Page State Change Operation
+ *
+ * GHCBData[55:52] - Page operation:
+ *   0x0001  Page assignment, Private
+ *   0x0002  Page assignment, Shared
I wonder how you've achieved that:

massage_diff: Warning: Unicode char [–] (0x2013) in line: + *   0x0001 – Page assignment, Private
massage_diff: Warning: Unicode char [–] (0x2013) in line: + *   0x0002 – Page assignment, Shared

See https://trojansource.codes/ for some background.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette
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