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Message-ID: <20250512190834.332684-33-ardb+git@google.com>
Date: Mon, 12 May 2025 21:08:45 +0200
From: Ard Biesheuvel <ardb+git@...gle.com>
To: linux-kernel@...r.kernel.org
Cc: linux-efi@...r.kernel.org, x86@...nel.org,
Ard Biesheuvel <ardb@...nel.org>, Borislav Petkov <bp@...en8.de>, Ingo Molnar <mingo@...nel.org>,
Dionna Amalie Glaze <dionnaglaze@...gle.com>, Kevin Loughlin <kevinloughlin@...gle.com>,
Tom Lendacky <thomas.lendacky@....com>
Subject: [RFT PATCH v3 10/21] x86/sev: Use boot SVSM CA for all startup and
init code
From: Ard Biesheuvel <ardb@...nel.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@...nel.org>
---
arch/x86/boot/compressed/sev.c | 13 ------
arch/x86/boot/startup/sev-startup.c | 7 +--
arch/x86/coco/sev/core.c | 47 +++++++++-----------
arch/x86/include/asm/sev-internal.h | 16 -------
4 files changed, 24 insertions(+), 59 deletions(-)
diff --git a/arch/x86/boot/compressed/sev.c b/arch/x86/boot/compressed/sev.c
index 04bc39d065ff..fc0119bdc878 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 u64 boot_svsm_caa_pa;
-
-struct svsm_ca *svsm_get_caa(void)
-{
- /* The decompressor is mapped 1:1 so VA == PA */
- return (struct svsm_ca *)boot_svsm_caa_pa;
-}
-
-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-startup.c b/arch/x86/boot/startup/sev-startup.c
index 7a3ad17d06f6..2e946dab036c 100644
--- a/arch/x86/boot/startup/sev-startup.c
+++ b/arch/x86/boot/startup/sev-startup.c
@@ -50,9 +50,6 @@ 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.
@@ -167,7 +164,7 @@ void __head early_snp_set_memory_private(unsigned long vaddr, unsigned long padd
* table.
*/
early_set_pages_state(vaddr, paddr, npages, SNP_PAGE_STATE_PRIVATE,
- svsm_get_caa(), svsm_get_caa_pa());
+ rip_rel_ptr(&boot_svsm_ca_page), boot_svsm_caa_pa);
}
void __head early_snp_set_memory_shared(unsigned long vaddr, unsigned long paddr,
@@ -184,7 +181,7 @@ void __head early_snp_set_memory_shared(unsigned long vaddr, unsigned long paddr
/* Ask hypervisor to mark the memory pages shared in the RMP table. */
early_set_pages_state(vaddr, paddr, npages, SNP_PAGE_STATE_SHARED,
- svsm_get_caa(), svsm_get_caa_pa());
+ rip_rel_ptr(&boot_svsm_ca_page), boot_svsm_caa_pa);
}
/*
diff --git a/arch/x86/coco/sev/core.c b/arch/x86/coco/sev/core.c
index 39bbbea09c24..fa7fdd11a45b 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 rip_rel_ptr(&boot_svsm_ca_page);
+}
+
+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_ca_page;
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 08e2cfdef512..3690994275dd 100644
--- a/arch/x86/include/asm/sev-internal.h
+++ b/arch/x86/include/asm/sev-internal.h
@@ -63,22 +63,6 @@ DECLARE_PER_CPU(u64, svsm_caa_pa);
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 rip_rel_ptr(&boot_svsm_ca_page);
-}
-
-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);
--
2.49.0.1045.g170613ef41-goog
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