linux-kernel - [PATCH v11 2/3] x86/mm: refactor __set_clr_pte

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Date: Tue, 2 Jul 2024 19:57:54 +0000
From: Ashish Kalra <Ashish.Kalra@....com>
To: <dave.hansen@...ux.intel.com>, <tglx@...utronix.de>, <mingo@...hat.com>,
	<bp@...en8.de>, <x86@...nel.org>
CC: <hpa@...or.com>, <rafael@...nel.org>, <peterz@...radead.org>,
	<adrian.hunter@...el.com>, <sathyanarayanan.kuppuswamy@...ux.intel.com>,
	<jun.nakajima@...el.com>, <kirill.shutemov@...ux.intel.com>,
	<rick.p.edgecombe@...el.com>, <linux-kernel@...r.kernel.org>,
	<thomas.lendacky@....com>, <michael.roth@....com>, <seanjc@...gle.com>,
	<kai.huang@...el.com>, <bhe@...hat.com>, <bdas@...hat.com>,
	<vkuznets@...hat.com>, <dionnaglaze@...gle.com>, <anisinha@...hat.com>,
	<ardb@...nel.org>, <dyoung@...hat.com>, <kexec@...ts.infradead.org>,
	<linux-coco@...ts.linux.dev>, <jroedel@...e.de>
Subject: [PATCH v11 2/3] x86/mm: refactor __set_clr_pte_enc()

From: Ashish Kalra <ashish.kalra@....com>

Refactor __set_clr_pte_enc() and add two new helper functions to
set/clear PTE C-bit from early SEV/SNP initialization code and
later during normal system operations and shutdown/kexec.

Signed-off-by: Ashish Kalra <ashish.kalra@....com>
---
 arch/x86/include/asm/sev.h    |  9 +++++++
 arch/x86/mm/mem_encrypt_amd.c | 47 +++++++++++++++++++++++++++++------
 2 files changed, 48 insertions(+), 8 deletions(-)

diff --git a/arch/x86/include/asm/sev.h b/arch/x86/include/asm/sev.h
index ac5886ce252e..4f3fd913aadb 100644
--- a/arch/x86/include/asm/sev.h
+++ b/arch/x86/include/asm/sev.h
@@ -348,6 +348,10 @@ u64 snp_get_unsupported_features(u64 status);
 u64 sev_get_status(void);
 void sev_show_status(void);
 void snp_update_svsm_ca(void);
+int prep_set_clr_pte_enc(pte_t *kpte, int level, int enc, void *va,
+			 unsigned long *ret_pfn, unsigned long *ret_pa,
+			 unsigned long *ret_size, pgprot_t *ret_new_prot);
+void set_pte_enc_mask(pte_t *kpte, unsigned long pfn, pgprot_t new_prot);
 
 #else	/* !CONFIG_AMD_MEM_ENCRYPT */
 
@@ -384,6 +388,11 @@ static inline u64 snp_get_unsupported_features(u64 status) { return 0; }
 static inline u64 sev_get_status(void) { return 0; }
 static inline void sev_show_status(void) { }
 static inline void snp_update_svsm_ca(void) { }
+static inline int
+prep_set_clr_pte_enc(pte_t *kpte, int level, int enc, void *va,
+		     unsigned long *ret_pfn, unsigned long *ret_pa,
+		     unsigned long *ret_size, pgprot_t *ret_new_prot) { }
+static inline void set_pte_enc_mask(pte_t *kpte, unsigned long pfn, pgprot_t new_prot) { }
 
 #endif	/* CONFIG_AMD_MEM_ENCRYPT */
 
diff --git a/arch/x86/mm/mem_encrypt_amd.c b/arch/x86/mm/mem_encrypt_amd.c
index 86a476a426c2..42a35040aaf9 100644
--- a/arch/x86/mm/mem_encrypt_amd.c
+++ b/arch/x86/mm/mem_encrypt_amd.c
@@ -311,15 +311,16 @@ static int amd_enc_status_change_finish(unsigned long vaddr, int npages, bool en
 	return 0;
 }
 
-static void __init __set_clr_pte_enc(pte_t *kpte, int level, bool enc)
+int prep_set_clr_pte_enc(pte_t *kpte, int level, int enc, void *va,
+			 unsigned long *ret_pfn, unsigned long *ret_pa,
+			 unsigned long *ret_size, pgprot_t *ret_new_prot)
 {
 	pgprot_t old_prot, new_prot;
 	unsigned long pfn, pa, size;
-	pte_t new_pte;
 
 	pfn = pg_level_to_pfn(level, kpte, &old_prot);
 	if (!pfn)
-		return;
+		return 1;
 
 	new_prot = old_prot;
 	if (enc)
@@ -329,7 +330,7 @@ static void __init __set_clr_pte_enc(pte_t *kpte, int level, bool enc)
 
 	/* If prot is same then do nothing. */
 	if (pgprot_val(old_prot) == pgprot_val(new_prot))
-		return;
+		return 1;
 
 	pa = pfn << PAGE_SHIFT;
 	size = page_level_size(level);
@@ -339,7 +340,39 @@ static void __init __set_clr_pte_enc(pte_t *kpte, int level, bool enc)
 	 * physical page attribute from C=1 to C=0 or vice versa. Flush the
 	 * caches to ensure that data gets accessed with the correct C-bit.
 	 */
-	clflush_cache_range(__va(pa), size);
+	if (va)
+		clflush_cache_range(va, size);
+	else
+		clflush_cache_range(__va(pa), size);
+
+	if (ret_new_prot)
+		*ret_new_prot = new_prot;
+	if (ret_size)
+		*ret_size = size;
+	if (ret_pfn)
+		*ret_pfn = pfn;
+	if (ret_pa)
+		*ret_pa = pa;
+
+	return 0;
+}
+
+void set_pte_enc_mask(pte_t *kpte, unsigned long pfn, pgprot_t new_prot)
+{
+	pte_t new_pte;
+
+	/* Change the page encryption mask. */
+	new_pte = pfn_pte(pfn, new_prot);
+	set_pte_atomic(kpte, new_pte);
+}
+
+static void __init __set_clr_pte_enc(pte_t *kpte, int level, bool enc)
+{
+	unsigned long pfn, pa, size;
+	pgprot_t new_prot;
+
+	if (prep_set_clr_pte_enc(kpte, level, enc, NULL, &pfn, &pa, &size, &new_prot))
+		return;
 
 	/* Encrypt/decrypt the contents in-place */
 	if (enc) {
@@ -354,9 +387,7 @@ static void __init __set_clr_pte_enc(pte_t *kpte, int level, bool enc)
 		early_snp_set_memory_shared((unsigned long)__va(pa), pa, 1);
 	}
 
-	/* Change the page encryption mask. */
-	new_pte = pfn_pte(pfn, new_prot);
-	set_pte_atomic(kpte, new_pte);
+	set_pte_enc_mask(kpte, pfn, new_prot);
 
 	/*
 	 * If page is set encrypted in the page table, then update the RMP table to
-- 
2.34.1