linux-kernel - [PATCH v4 06/14] x86/sev: Cache the secrets page address

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Date:   Mon, 14 Aug 2023 11:22:14 +0530
From:   Nikunj A Dadhania <nikunj@....com>
To:     <linux-kernel@...r.kernel.org>, <x86@...nel.org>
CC:     <bp@...en8.de>, <thomas.lendacky@....com>,
        <dionnaglaze@...gle.com>, <pgonda@...gle.com>, <seanjc@...gle.com>,
        <pbonzini@...hat.com>, <nikunj@....com>
Subject: [PATCH v4 06/14] x86/sev: Cache the secrets page address

Save the secrets page address during snp_init() from the CC blob. Use
secrets_pa instead of calling get_secrets_page() that remaps the CC
blob for getting the secrets page every time.

Signed-off-by: Nikunj A Dadhania <nikunj@....com>
Reviewed-by: Tom Lendacky <thomas.lendacky@....com>
---
 arch/x86/kernel/sev.c | 52 +++++++++++++------------------------------
 1 file changed, 16 insertions(+), 36 deletions(-)

diff --git a/arch/x86/kernel/sev.c b/arch/x86/kernel/sev.c
index a10cf9f21e22..a63a3edf13d0 100644
--- a/arch/x86/kernel/sev.c
+++ b/arch/x86/kernel/sev.c
@@ -72,6 +72,9 @@ static struct ghcb *boot_ghcb __section(".data");
 /* Bitmap of SEV features supported by the hypervisor */
 static u64 sev_hv_features __ro_after_init;
 
+/* Secrets page physical address from the CC blob */
+static u64 secrets_pa __ro_after_init;
+
 /* #VC handler runtime per-CPU data */
 struct sev_es_runtime_data {
 	struct ghcb ghcb_page;
@@ -561,45 +564,16 @@ void noinstr __sev_es_nmi_complete(void)
 	__sev_put_ghcb(&state);
 }
 
-static u64 __init get_secrets_page(void)
-{
-	u64 pa_data = boot_params.cc_blob_address;
-	struct cc_blob_sev_info info;
-	void *map;
-
-	/*
-	 * The CC blob contains the address of the secrets page, check if the
-	 * blob is present.
-	 */
-	if (!pa_data)
-		return 0;
-
-	map = early_memremap(pa_data, sizeof(info));
-	if (!map) {
-		pr_err("Unable to locate SNP secrets page: failed to map the Confidential Computing blob.\n");
-		return 0;
-	}
-	memcpy(&info, map, sizeof(info));
-	early_memunmap(map, sizeof(info));
-
-	/* smoke-test the secrets page passed */
-	if (!info.secrets_phys || info.secrets_len != PAGE_SIZE)
-		return 0;
-
-	return info.secrets_phys;
-}
-
 static u64 __init get_snp_jump_table_addr(void)
 {
 	struct snp_secrets_page_layout *layout;
 	void __iomem *mem;
-	u64 pa, addr;
+	u64 addr;
 
-	pa = get_secrets_page();
-	if (!pa)
+	if (!secrets_pa)
 		return 0;
 
-	mem = ioremap_encrypted(pa, PAGE_SIZE);
+	mem = ioremap_encrypted(secrets_pa, PAGE_SIZE);
 	if (!mem) {
 		pr_err("Unable to locate AP jump table address: failed to map the SNP secrets page.\n");
 		return 0;
@@ -2093,6 +2067,12 @@ static __init struct cc_blob_sev_info *find_cc_blob(struct boot_params *bp)
 	return cc_info;
 }
 
+static void __init set_secrets_pa(const struct cc_blob_sev_info *cc_info)
+{
+	if (cc_info && cc_info->secrets_phys && cc_info->secrets_len == PAGE_SIZE)
+		secrets_pa = cc_info->secrets_phys;
+}
+
 bool __init snp_init(struct boot_params *bp)
 {
 	struct cc_blob_sev_info *cc_info;
@@ -2104,6 +2084,8 @@ bool __init snp_init(struct boot_params *bp)
 	if (!cc_info)
 		return false;
 
+	set_secrets_pa(cc_info);
+
 	setup_cpuid_table(cc_info);
 
 	/*
@@ -2256,16 +2238,14 @@ static struct platform_device sev_guest_device = {
 static int __init snp_init_platform_device(void)
 {
 	struct sev_guest_platform_data data;
-	u64 gpa;
 
 	if (!cc_platform_has(CC_ATTR_GUEST_SEV_SNP))
 		return -ENODEV;
 
-	gpa = get_secrets_page();
-	if (!gpa)
+	if (!secrets_pa)
 		return -ENODEV;
 
-	data.secrets_gpa = gpa;
+	data.secrets_gpa = secrets_pa;
 	if (platform_device_add_data(&sev_guest_device, &data, sizeof(data)))
 		return -ENODEV;
 
-- 
2.34.1