[RFT PATCH v2 10/23] x86/sev: Use boot SVSM CA for all startup and init code

[Ard Biesheuvel <ardb+git@google.com>]

From: Ard Biesheuvel <ardb@kernel.org>

To avoid having to reason about whether or not to use the per-CPU SVSM
calling area when running startup and init code on the boot CPU, reuse
the boot SVSM calling area as the per-CPU area for CPU #0.

This removes the need to make the per-CPU variables and associated state
in sev_cfg accessible to the startup code once confined.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
 arch/x86/boot/compressed/sev.c      | 13 ------
 arch/x86/boot/startup/sev-shared.c  |  4 +-
 arch/x86/boot/startup/sev-startup.c |  6 +--
 arch/x86/coco/sev/core.c            | 47 +++++++++-----------
 arch/x86/include/asm/sev-internal.h | 16 -------
 5 files changed, 26 insertions(+), 60 deletions(-)

diff --git a/arch/x86/boot/compressed/sev.c b/arch/x86/boot/compressed/sev.c
index 9b6eebc24e78..91e8140250f6 100644
--- a/arch/x86/boot/compressed/sev.c
+++ b/arch/x86/boot/compressed/sev.c
@@ -37,19 +37,6 @@ struct ghcb *boot_ghcb;
 
 #define __BOOT_COMPRESSED
 
-extern struct svsm_ca *boot_svsm_caa;
-extern u64 boot_svsm_caa_pa;
-
-struct svsm_ca *svsm_get_caa(void)
-{
-	return boot_svsm_caa;
-}
-
-u64 svsm_get_caa_pa(void)
-{
-	return boot_svsm_caa_pa;
-}
-
 u8 snp_vmpl;
 
 /* Include code for early handlers */
diff --git a/arch/x86/boot/startup/sev-shared.c b/arch/x86/boot/startup/sev-shared.c
index 0709c8a8655a..b1f4b9b15045 100644
--- a/arch/x86/boot/startup/sev-shared.c
+++ b/arch/x86/boot/startup/sev-shared.c
@@ -585,10 +585,10 @@ static void __head svsm_pval_4k_page(unsigned long paddr, bool validate)
 	 */
 	flags = native_local_irq_save();
 
-	call.caa = svsm_get_caa();
+	call.caa = boot_svsm_caa;
 
 	pc = (struct svsm_pvalidate_call *)call.caa->svsm_buffer;
-	pc_pa = svsm_get_caa_pa() + offsetof(struct svsm_ca, svsm_buffer);
+	pc_pa = boot_svsm_caa_pa + offsetof(struct svsm_ca, svsm_buffer);
 
 	pc->num_entries = 1;
 	pc->cur_index   = 0;
diff --git a/arch/x86/boot/startup/sev-startup.c b/arch/x86/boot/startup/sev-startup.c
index 797ca3e29b12..ca6a9863ffab 100644
--- a/arch/x86/boot/startup/sev-startup.c
+++ b/arch/x86/boot/startup/sev-startup.c
@@ -59,9 +59,6 @@ u64 sev_secrets_pa __ro_after_init;
 /* For early boot SVSM communication */
 struct svsm_ca boot_svsm_ca_page __aligned(PAGE_SIZE);
 
-DEFINE_PER_CPU(struct svsm_ca *, svsm_caa);
-DEFINE_PER_CPU(u64, svsm_caa_pa);
-
 /*
  * Nothing shall interrupt this code path while holding the per-CPU
  * GHCB. The backup GHCB is only for NMIs interrupting this path.
@@ -261,6 +258,7 @@ static __head struct cc_blob_sev_info *find_cc_blob(struct boot_params *bp)
 
 static __head void svsm_setup(struct cc_blob_sev_info *cc_info)
 {
+	struct snp_secrets_page *secrets = (void *)cc_info->secrets_phys;
 	struct svsm_call call = {};
 	int ret;
 	u64 pa;
@@ -289,7 +287,7 @@ static __head void svsm_setup(struct cc_blob_sev_info *cc_info)
 	 *   RAX = 0 (Protocol=0, CallID=0)
 	 *   RCX = New CA GPA
 	 */
-	call.caa = svsm_get_caa();
+	call.caa = (struct svsm_ca *)secrets->svsm_caa;
 	call.rax = SVSM_CORE_CALL(SVSM_CORE_REMAP_CA);
 	call.rcx = pa;
 	ret = svsm_perform_msr_protocol(&call);
diff --git a/arch/x86/coco/sev/core.c b/arch/x86/coco/sev/core.c
index 883b2719986d..36edf670ff19 100644
--- a/arch/x86/coco/sev/core.c
+++ b/arch/x86/coco/sev/core.c
@@ -45,6 +45,25 @@
 #include <asm/cpuid.h>
 #include <asm/cmdline.h>
 
+DEFINE_PER_CPU(struct svsm_ca *, svsm_caa);
+DEFINE_PER_CPU(u64, svsm_caa_pa);
+
+static inline struct svsm_ca *svsm_get_caa(void)
+{
+	if (sev_cfg.use_cas)
+		return this_cpu_read(svsm_caa);
+	else
+		return boot_svsm_caa;
+}
+
+static inline u64 svsm_get_caa_pa(void)
+{
+	if (sev_cfg.use_cas)
+		return this_cpu_read(svsm_caa_pa);
+	else
+		return boot_svsm_caa_pa;
+}
+
 /* AP INIT values as documented in the APM2  section "Processor Initialization State" */
 #define AP_INIT_CS_LIMIT		0xffff
 #define AP_INIT_DS_LIMIT		0xffff
@@ -1207,7 +1226,8 @@ static void __init alloc_runtime_data(int cpu)
 		struct svsm_ca *caa;
 
 		/* Allocate the SVSM CA page if an SVSM is present */
-		caa = memblock_alloc_or_panic(sizeof(*caa), PAGE_SIZE);
+		caa = cpu ? memblock_alloc_or_panic(sizeof(*caa), PAGE_SIZE)
+			  : boot_svsm_caa;
 
 		per_cpu(svsm_caa, cpu) = caa;
 		per_cpu(svsm_caa_pa, cpu) = __pa(caa);
@@ -1261,32 +1281,9 @@ void __init sev_es_init_vc_handling(void)
 		init_ghcb(cpu);
 	}
 
-	/* If running under an SVSM, switch to the per-cpu CA */
-	if (snp_vmpl) {
-		struct svsm_call call = {};
-		unsigned long flags;
-		int ret;
-
-		local_irq_save(flags);
-
-		/*
-		 * SVSM_CORE_REMAP_CA call:
-		 *   RAX = 0 (Protocol=0, CallID=0)
-		 *   RCX = New CA GPA
-		 */
-		call.caa = svsm_get_caa();
-		call.rax = SVSM_CORE_CALL(SVSM_CORE_REMAP_CA);
-		call.rcx = this_cpu_read(svsm_caa_pa);
-		ret = svsm_perform_call_protocol(&call);
-		if (ret)
-			panic("Can't remap the SVSM CA, ret=%d, rax_out=0x%llx\n",
-			      ret, call.rax_out);
-
+	if (snp_vmpl)
 		sev_cfg.use_cas = true;
 
-		local_irq_restore(flags);
-	}
-
 	sev_es_setup_play_dead();
 
 	/* Secondary CPUs use the runtime #VC handler */
diff --git a/arch/x86/include/asm/sev-internal.h b/arch/x86/include/asm/sev-internal.h
index 0d02e780beb3..4335711274e3 100644
--- a/arch/x86/include/asm/sev-internal.h
+++ b/arch/x86/include/asm/sev-internal.h
@@ -64,22 +64,6 @@ DECLARE_PER_CPU(u64, svsm_caa_pa);
 extern struct svsm_ca *boot_svsm_caa;
 extern u64 boot_svsm_caa_pa;
 
-static __always_inline struct svsm_ca *svsm_get_caa(void)
-{
-	if (sev_cfg.use_cas)
-		return this_cpu_read(svsm_caa);
-	else
-		return boot_svsm_caa;
-}
-
-static __always_inline u64 svsm_get_caa_pa(void)
-{
-	if (sev_cfg.use_cas)
-		return this_cpu_read(svsm_caa_pa);
-	else
-		return boot_svsm_caa_pa;
-}
-
 enum es_result verify_exception_info(struct ghcb *ghcb, struct es_em_ctxt *ctxt);
 void vc_forward_exception(struct es_em_ctxt *ctxt);
 
-- 
2.49.0.906.g1f30a19c02-goog