Commit c54604fb authored by Ard Biesheuvel's avatar Ard Biesheuvel Committed by Borislav Petkov (AMD)
Browse files

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



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: default avatarArd Biesheuvel <ardb@kernel.org>
Signed-off-by: default avatarBorislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/20250828102202.1849035-33-ardb+git@google.com
parent 00d25566

arch/x86/boot/compressed/sev.c

+0 −13
Original line number Diff line number Diff line
@@ -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 */

arch/x86/boot/startup/sev-startup.c

+6 −5
Original line number Diff line number Diff line
@@ -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

	};



	/*

arch/x86/coco/sev/core.c

+22 −25
Original line number Diff line number Diff line
@@ -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 */

arch/x86/include/asm/sev-internal.h

+0 −16
Original line number Diff line number Diff line
@@ -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);