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x86/sev: Use boot SVSM CA for all startup and init code

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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 the BSP.

Thus, remove the need to make the per-CPU variables and associated state in
sev_cfg accessible to the startup code once confined.

  [ bp: Massage commit message. ]

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/20250828102202.1849035-33-ardb+git@google.com
This commit is contained in:
Ard Biesheuvel 2025-08-28 12:22:12 +02:00 committed by Borislav Petkov (AMD)
parent 00d2556676
commit c54604fb7f
4 changed files with 28 additions and 59 deletions
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13
arch/x86/boot/compressed/sev.c
View File

@ -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 */

11
arch/x86/boot/startup/sev-startup.c
View File

@ -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.
@ -153,7 +150,9 @@ void __head early_snp_set_memory_private(unsigned long vaddr, unsigned long padd
unsigned long npages)
{
struct psc_desc d = {
SNP_PAGE_STATE_PRIVATE, svsm_get_caa(), svsm_get_caa_pa()
SNP_PAGE_STATE_PRIVATE,
rip_rel_ptr(&boot_svsm_ca_page),
boot_svsm_caa_pa
};
/*
@ -176,7 +175,9 @@ void __head early_snp_set_memory_shared(unsigned long vaddr, unsigned long paddr
unsigned long npages)
{
struct psc_desc d = {
SNP_PAGE_STATE_SHARED, svsm_get_caa(), svsm_get_caa_pa()
SNP_PAGE_STATE_SHARED,
rip_rel_ptr(&boot_svsm_ca_page),
boot_svsm_caa_pa
};
/*

47
arch/x86/coco/sev/core.c
View File

@ -46,6 +46,25 @@
#include <asm/cmdline.h>
#include <asm/msr.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
@ -1312,7 +1331,8 @@ 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);
@ -1366,32 +1386,9 @@ 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 */

16
arch/x86/include/asm/sev-internal.h
View File

@ -62,22 +62,6 @@ 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);