Commit 95d33bfa authored by Brijesh Singh's avatar Brijesh Singh Committed by Borislav Petkov
Browse files

x86/sev: Register GHCB memory when SEV-SNP is active 



The SEV-SNP guest is required by the GHCB spec to register the GHCB's
Guest Physical Address (GPA). This is because the hypervisor may prefer
that a guest uses a consistent and/or specific GPA for the GHCB associated
with a vCPU. For more information, see the GHCB specification section
"GHCB GPA Registration".

  [ bp: Cleanup comments. ]

Signed-off-by: default avatarBrijesh Singh <brijesh.singh@amd.com>
Signed-off-by: default avatarBorislav Petkov <bp@suse.de>
Link: https://lore.kernel.org/r/20220307213356.2797205-18-brijesh.singh@amd.com
parent 87294bdb

arch/x86/include/asm/sev.h

+2 −0
Original line number Diff line number Diff line
@@ -122,6 +122,7 @@ static inline int pvalidate(unsigned long vaddr, bool rmp_psize, bool validate) 


	return rc;

}

void setup_ghcb(void);

#else

static inline void sev_es_ist_enter(struct pt_regs *regs) { }

static inline void sev_es_ist_exit(void) { }
@@ -130,6 +131,7 @@ static inline void sev_es_nmi_complete(void) { } 
static inline int sev_es_efi_map_ghcbs(pgd_t *pgd) { return 0; }

static inline int pvalidate(unsigned long vaddr, bool rmp_psize, bool validate) { return 0; }

static inline int rmpadjust(unsigned long vaddr, bool rmp_psize, unsigned long attrs) { return 0; }

static inline void setup_ghcb(void) { }

#endif



#endif

arch/x86/kernel/cpu/common.c

+4 −0
Original line number Diff line number Diff line
@@ -60,6 +60,7 @@ 
#include <asm/uv/uv.h>

#include <asm/sigframe.h>

#include <asm/traps.h>

#include <asm/sev.h>



#include "cpu.h"
@@ -2124,6 +2125,9 @@ void cpu_init_exception_handling(void) 


	load_TR_desc();



	/* GHCB needs to be setup to handle #VC. */

	setup_ghcb();



	/* Finally load the IDT */

	load_current_idt();

}

arch/x86/kernel/head64.c

+3 −1
Original line number Diff line number Diff line
@@ -597,8 +597,10 @@ static void startup_64_load_idt(unsigned long physbase) 
void early_setup_idt(void)

{

	/* VMM Communication Exception */

	if (IS_ENABLED(CONFIG_AMD_MEM_ENCRYPT))

	if (IS_ENABLED(CONFIG_AMD_MEM_ENCRYPT)) {

		setup_ghcb();

		set_bringup_idt_handler(bringup_idt_table, X86_TRAP_VC, vc_boot_ghcb);

	}



	bringup_idt_descr.address = (unsigned long)bringup_idt_table;

	native_load_idt(&bringup_idt_descr);

arch/x86/kernel/sev-shared.c

+1 −1
Original line number Diff line number Diff line
@@ -68,7 +68,7 @@ static u64 get_hv_features(void) 
	return GHCB_MSR_HV_FT_RESP_VAL(val);

}



static void __maybe_unused snp_register_ghcb_early(unsigned long paddr)

static void snp_register_ghcb_early(unsigned long paddr)

{

	unsigned long pfn = paddr >> PAGE_SHIFT;

	u64 val;

arch/x86/kernel/sev.c

+34 −12
Original line number Diff line number Diff line
@@ -41,7 +41,7 @@ static struct ghcb boot_ghcb_page __bss_decrypted __aligned(PAGE_SIZE); 
 * Needs to be in the .data section because we need it NULL before bss is

 * cleared

 */

static struct ghcb __initdata *boot_ghcb;

static struct ghcb *boot_ghcb __section(".data");



/* Bitmap of SEV features supported by the hypervisor */

static u64 sev_hv_features __ro_after_init;
@@ -647,15 +647,39 @@ static enum es_result vc_handle_msr(struct ghcb *ghcb, struct es_em_ctxt *ctxt) 
	return ret;

}



/*

 * This function runs on the first #VC exception after the kernel

 * switched to virtual addresses.

 */

static bool __init sev_es_setup_ghcb(void)

static void snp_register_per_cpu_ghcb(void)

{

	struct sev_es_runtime_data *data;

	struct ghcb *ghcb;



	data = this_cpu_read(runtime_data);

	ghcb = &data->ghcb_page;



	snp_register_ghcb_early(__pa(ghcb));

}



void setup_ghcb(void)

{

	if (!cc_platform_has(CC_ATTR_GUEST_STATE_ENCRYPT))

		return;



	/* First make sure the hypervisor talks a supported protocol. */

	if (!sev_es_negotiate_protocol())

		return false;

		sev_es_terminate(SEV_TERM_SET_GEN, GHCB_SEV_ES_GEN_REQ);



	/*

	 * Check whether the runtime #VC exception handler is active. It uses

	 * the per-CPU GHCB page which is set up by sev_es_init_vc_handling().

	 *

	 * If SNP is active, register the per-CPU GHCB page so that the runtime

	 * exception handler can use it.

	 */

	if (initial_vc_handler == (unsigned long)kernel_exc_vmm_communication) {

		if (cc_platform_has(CC_ATTR_GUEST_SEV_SNP))

			snp_register_per_cpu_ghcb();



		return;

	}



	/*

	 * Clear the boot_ghcb. The first exception comes in before the bss
@@ -666,7 +690,9 @@ static bool __init sev_es_setup_ghcb(void) 
	/* Alright - Make the boot-ghcb public */

	boot_ghcb = &boot_ghcb_page;



	return true;

	/* SNP guest requires that GHCB GPA must be registered. */

	if (cc_platform_has(CC_ATTR_GUEST_SEV_SNP))

		snp_register_ghcb_early(__pa(&boot_ghcb_page));

}



#ifdef CONFIG_HOTPLUG_CPU
@@ -1397,10 +1423,6 @@ bool __init handle_vc_boot_ghcb(struct pt_regs *regs) 
	struct es_em_ctxt ctxt;

	enum es_result result;



	/* Do initial setup or terminate the guest */

	if (unlikely(boot_ghcb == NULL && !sev_es_setup_ghcb()))

		sev_es_terminate(SEV_TERM_SET_GEN, GHCB_SEV_ES_GEN_REQ);



	vc_ghcb_invalidate(boot_ghcb);



	result = vc_init_em_ctxt(&ctxt, regs, exit_code);