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x86/sev: Add SNP-specific unaccepted memory support

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Add SNP-specific hooks to the unaccepted memory support in the boot
path (__accept_memory()) and the core kernel (accept_memory()) in order
to support booting SNP guests when unaccepted memory is present. Without
this support, SNP guests will fail to boot and/or panic() when unaccepted
memory is present in the EFI memory map.

The process of accepting memory under SNP involves invoking the hypervisor
to perform a page state change for the page to private memory and then
issuing a PVALIDATE instruction to accept the page.

Since the boot path and the core kernel paths perform similar operations,
move the pvalidate_pages() and vmgexit_psc() functions into sev-shared.c
to avoid code duplication.

Create the new header file arch/x86/boot/compressed/sev.h because adding
the function declaration to any of the existing SEV related header files
pulls in too many other header files, causing the build to fail.

Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/a52fa69f460fd1876d70074b20ad68210dfc31dd.1686063086.git.thomas.lendacky@amd.com
This commit is contained in:
Tom Lendacky
2023-06-06 09:51:26 -05:00
committed by Borislav Petkov (AMD)
parent 15d9088779
commit 6c32117963
8 changed files with 204 additions and 99 deletions
Download Patch File Download Diff File Expand all files Collapse all files

2
arch/x86/Kconfig
View File

@ -1543,11 +1543,13 @@ config X86_MEM_ENCRYPT
config AMD_MEM_ENCRYPT
bool "AMD Secure Memory Encryption (SME) support"
depends on X86_64 && CPU_SUP_AMD
depends on EFI_STUB
select DMA_COHERENT_POOL
select ARCH_USE_MEMREMAP_PROT
select INSTRUCTION_DECODER
select ARCH_HAS_CC_PLATFORM
select X86_MEM_ENCRYPT
select UNACCEPTED_MEMORY
help
Say yes to enable support for the encryption of system memory.
This requires an AMD processor that supports Secure Memory

3
arch/x86/boot/compressed/mem.c
View File

@ -3,6 +3,7 @@
#include "error.h"
#include "misc.h"
#include "tdx.h"
#include "sev.h"
#include <asm/shared/tdx.h>
/*
@ -37,6 +38,8 @@ void arch_accept_memory(phys_addr_t start, phys_addr_t end)
if (early_is_tdx_guest()) {
if (!tdx_accept_memory(start, end))
panic("TDX: Failed to accept memory\n");
} else if (sev_snp_enabled()) {
snp_accept_memory(start, end);
} else {
error("Cannot accept memory: unknown platform\n");
}

54
arch/x86/boot/compressed/sev.c
View File

@ -115,7 +115,7 @@ static enum es_result vc_read_mem(struct es_em_ctxt *ctxt,
/* Include code for early handlers */
#include "../../kernel/sev-shared.c"
static inline bool sev_snp_enabled(void)
bool sev_snp_enabled(void)
{
return sev_status & MSR_AMD64_SEV_SNP_ENABLED;
}
@ -181,6 +181,58 @@ static bool early_setup_ghcb(void)
return true;
}
static phys_addr_t __snp_accept_memory(struct snp_psc_desc *desc,
phys_addr_t pa, phys_addr_t pa_end)
{
struct psc_hdr *hdr;
struct psc_entry *e;
unsigned int i;
hdr = &desc->hdr;
memset(hdr, 0, sizeof(*hdr));
e = desc->entries;
i = 0;
while (pa < pa_end && i < VMGEXIT_PSC_MAX_ENTRY) {
hdr->end_entry = i;
e->gfn = pa >> PAGE_SHIFT;
e->operation = SNP_PAGE_STATE_PRIVATE;
if (IS_ALIGNED(pa, PMD_SIZE) && (pa_end - pa) >= PMD_SIZE) {
e->pagesize = RMP_PG_SIZE_2M;
pa += PMD_SIZE;
} else {
e->pagesize = RMP_PG_SIZE_4K;
pa += PAGE_SIZE;
}
e++;
i++;
}
if (vmgexit_psc(boot_ghcb, desc))
sev_es_terminate(SEV_TERM_SET_LINUX, GHCB_TERM_PSC);
pvalidate_pages(desc);
return pa;
}
void snp_accept_memory(phys_addr_t start, phys_addr_t end)
{
struct snp_psc_desc desc = {};
unsigned int i;
phys_addr_t pa;
if (!boot_ghcb && !early_setup_ghcb())
sev_es_terminate(SEV_TERM_SET_LINUX, GHCB_TERM_PSC);
pa = start;
while (pa < end)
pa = __snp_accept_memory(&desc, pa, end);
}
void sev_es_shutdown_ghcb(void)
{
if (!boot_ghcb)

23
arch/x86/boot/compressed/sev.h Normal file
View File

@ -0,0 +1,23 @@
/* SPDX-License-Identifier: GPL-2.0 */
/*
* AMD SEV header for early boot related functions.
*
* Author: Tom Lendacky <thomas.lendacky@amd.com>
*/
#ifndef BOOT_COMPRESSED_SEV_H
#define BOOT_COMPRESSED_SEV_H
#ifdef CONFIG_AMD_MEM_ENCRYPT
bool sev_snp_enabled(void);
void snp_accept_memory(phys_addr_t start, phys_addr_t end);
#else
static inline bool sev_snp_enabled(void) { return false; }
static inline void snp_accept_memory(phys_addr_t start, phys_addr_t end) { }
#endif
#endif

3
arch/x86/include/asm/sev.h
View File

@ -206,6 +206,7 @@ void snp_set_wakeup_secondary_cpu(void);
bool snp_init(struct boot_params *bp);
void __init __noreturn snp_abort(void);
int snp_issue_guest_request(u64 exit_code, struct snp_req_data *input, struct snp_guest_request_ioctl *rio);
void snp_accept_memory(phys_addr_t start, phys_addr_t end);
#else
static inline void sev_es_ist_enter(struct pt_regs *regs) { }
static inline void sev_es_ist_exit(void) { }
@ -229,6 +230,8 @@ static inline int snp_issue_guest_request(u64 exit_code, struct snp_req_data *in
{
return -ENOTTY;
}
static inline void snp_accept_memory(phys_addr_t start, phys_addr_t end) { }
#endif
#endif

3
arch/x86/include/asm/unaccepted_memory.h
View File

@ -3,6 +3,7 @@
#include <linux/efi.h>
#include <asm/tdx.h>
#include <asm/sev.h>
static inline void arch_accept_memory(phys_addr_t start, phys_addr_t end)
{
@ -10,6 +11,8 @@ static inline void arch_accept_memory(phys_addr_t start, phys_addr_t end)
if (cpu_feature_enabled(X86_FEATURE_TDX_GUEST)) {
if (!tdx_accept_memory(start, end))
panic("TDX: Failed to accept memory\n");
} else if (cc_platform_has(CC_ATTR_GUEST_SEV_SNP)) {
snp_accept_memory(start, end);
} else {
panic("Cannot accept memory: unknown platform\n");
}

103
arch/x86/kernel/sev-shared.c
View File

@ -12,6 +12,9 @@
#ifndef __BOOT_COMPRESSED
#define error(v) pr_err(v)
#define has_cpuflag(f) boot_cpu_has(f)
#else
#undef WARN
#define WARN(condition, format...) (!!(condition))
#endif
/* I/O parameters for CPUID-related helpers */
@ -991,3 +994,103 @@ static void __init setup_cpuid_table(const struct cc_blob_sev_info *cc_info)
cpuid_ext_range_max = fn->eax;
}
}
static void pvalidate_pages(struct snp_psc_desc *desc)
{
struct psc_entry *e;
unsigned long vaddr;
unsigned int size;
unsigned int i;
bool validate;
int rc;
for (i = 0; i <= desc->hdr.end_entry; i++) {
e = &desc->entries[i];
vaddr = (unsigned long)pfn_to_kaddr(e->gfn);
size = e->pagesize ? RMP_PG_SIZE_2M : RMP_PG_SIZE_4K;
validate = e->operation == SNP_PAGE_STATE_PRIVATE;
rc = pvalidate(vaddr, size, validate);
if (rc == PVALIDATE_FAIL_SIZEMISMATCH && size == RMP_PG_SIZE_2M) {
unsigned long vaddr_end = vaddr + PMD_SIZE;
for (; vaddr < vaddr_end; vaddr += PAGE_SIZE) {
rc = pvalidate(vaddr, RMP_PG_SIZE_4K, validate);
if (rc)
break;
}
}
if (rc) {
WARN(1, "Failed to validate address 0x%lx ret %d", vaddr, rc);
sev_es_terminate(SEV_TERM_SET_LINUX, GHCB_TERM_PVALIDATE);
}
}
}
static int vmgexit_psc(struct ghcb *ghcb, struct snp_psc_desc *desc)
{
int cur_entry, end_entry, ret = 0;
struct snp_psc_desc *data;
struct es_em_ctxt ctxt;
vc_ghcb_invalidate(ghcb);
/* Copy the input desc into GHCB shared buffer */
data = (struct snp_psc_desc *)ghcb->shared_buffer;
memcpy(ghcb->shared_buffer, desc, min_t(int, GHCB_SHARED_BUF_SIZE, sizeof(*desc)));
/*
* As per the GHCB specification, the hypervisor can resume the guest
* before processing all the entries. Check whether all the entries
* are processed. If not, then keep retrying. Note, the hypervisor
* will update the data memory directly to indicate the status, so
* reference the data->hdr everywhere.
*
* The strategy here is to wait for the hypervisor to change the page
* state in the RMP table before guest accesses the memory pages. If the
* page state change was not successful, then later memory access will
* result in a crash.
*/
cur_entry = data->hdr.cur_entry;
end_entry = data->hdr.end_entry;
while (data->hdr.cur_entry <= data->hdr.end_entry) {
ghcb_set_sw_scratch(ghcb, (u64)__pa(data));
/* This will advance the shared buffer data points to. */
ret = sev_es_ghcb_hv_call(ghcb, &ctxt, SVM_VMGEXIT_PSC, 0, 0);
/*
* Page State Change VMGEXIT can pass error code through
* exit_info_2.
*/
if (WARN(ret || ghcb->save.sw_exit_info_2,
"SNP: PSC failed ret=%d exit_info_2=%llx\n",
ret, ghcb->save.sw_exit_info_2)) {
ret = 1;
goto out;
}
/* Verify that reserved bit is not set */
if (WARN(data->hdr.reserved, "Reserved bit is set in the PSC header\n")) {
ret = 1;
goto out;
}
/*
* Sanity check that entry processing is not going backwards.
* This will happen only if hypervisor is tricking us.
*/
if (WARN(data->hdr.end_entry > end_entry || cur_entry > data->hdr.cur_entry,
"SNP: PSC processing going backward, end_entry %d (got %d) cur_entry %d (got %d)\n",
end_entry, data->hdr.end_entry, cur_entry, data->hdr.cur_entry)) {
ret = 1;
goto out;
}
}
out:
return ret;
}

112
arch/x86/kernel/sev.c
View File

@ -657,38 +657,6 @@ static u64 __init get_jump_table_addr(void)
return ret;
}
static void pvalidate_pages(struct snp_psc_desc *desc)
{
struct psc_entry *e;
unsigned long vaddr;
unsigned int size;
unsigned int i;
bool validate;
int rc;
for (i = 0; i <= desc->hdr.end_entry; i++) {
e = &desc->entries[i];
vaddr = (unsigned long)pfn_to_kaddr(e->gfn);
size = e->pagesize ? RMP_PG_SIZE_2M : RMP_PG_SIZE_4K;
validate = e->operation == SNP_PAGE_STATE_PRIVATE;
rc = pvalidate(vaddr, size, validate);
if (rc == PVALIDATE_FAIL_SIZEMISMATCH && size == RMP_PG_SIZE_2M) {
unsigned long vaddr_end = vaddr + PMD_SIZE;
for (; vaddr < vaddr_end; vaddr += PAGE_SIZE) {
rc = pvalidate(vaddr, RMP_PG_SIZE_4K, validate);
if (rc)
break;
}
}
if (WARN(rc, "Failed to validate address 0x%lx ret %d", vaddr, rc))
sev_es_terminate(SEV_TERM_SET_LINUX, GHCB_TERM_PVALIDATE);
}
}
static void early_set_pages_state(unsigned long vaddr, unsigned long paddr,
unsigned long npages, enum psc_op op)
{
@ -796,72 +764,6 @@ void __init snp_prep_memory(unsigned long paddr, unsigned int sz, enum psc_op op
WARN(1, "invalid memory op %d\n", op);
}
static int vmgexit_psc(struct ghcb *ghcb, struct snp_psc_desc *desc)
{
int cur_entry, end_entry, ret = 0;
struct snp_psc_desc *data;
struct es_em_ctxt ctxt;
vc_ghcb_invalidate(ghcb);
/* Copy the input desc into GHCB shared buffer */
data = (struct snp_psc_desc *)ghcb->shared_buffer;
memcpy(ghcb->shared_buffer, desc, min_t(int, GHCB_SHARED_BUF_SIZE, sizeof(*desc)));
/*
* As per the GHCB specification, the hypervisor can resume the guest
* before processing all the entries. Check whether all the entries
* are processed. If not, then keep retrying. Note, the hypervisor
* will update the data memory directly to indicate the status, so
* reference the data->hdr everywhere.
*
* The strategy here is to wait for the hypervisor to change the page
* state in the RMP table before guest accesses the memory pages. If the
* page state change was not successful, then later memory access will
* result in a crash.
*/
cur_entry = data->hdr.cur_entry;
end_entry = data->hdr.end_entry;
while (data->hdr.cur_entry <= data->hdr.end_entry) {
ghcb_set_sw_scratch(ghcb, (u64)__pa(data));
/* This will advance the shared buffer data points to. */
ret = sev_es_ghcb_hv_call(ghcb, &ctxt, SVM_VMGEXIT_PSC, 0, 0);
/*
* Page State Change VMGEXIT can pass error code through
* exit_info_2.
*/
if (WARN(ret || ghcb->save.sw_exit_info_2,
"SNP: PSC failed ret=%d exit_info_2=%llx\n",
ret, ghcb->save.sw_exit_info_2)) {
ret = 1;
goto out;
}
/* Verify that reserved bit is not set */
if (WARN(data->hdr.reserved, "Reserved bit is set in the PSC header\n")) {
ret = 1;
goto out;
}
/*
* Sanity check that entry processing is not going backwards.
* This will happen only if hypervisor is tricking us.
*/
if (WARN(data->hdr.end_entry > end_entry || cur_entry > data->hdr.cur_entry,
"SNP: PSC processing going backward, end_entry %d (got %d) cur_entry %d (got %d)\n",
end_entry, data->hdr.end_entry, cur_entry, data->hdr.cur_entry)) {
ret = 1;
goto out;
}
}
out:
return ret;
}
static unsigned long __set_pages_state(struct snp_psc_desc *data, unsigned long vaddr,
unsigned long vaddr_end, int op)
{
@ -966,6 +868,20 @@ void snp_set_memory_private(unsigned long vaddr, unsigned long npages)
set_pages_state(vaddr, npages, SNP_PAGE_STATE_PRIVATE);
}
void snp_accept_memory(phys_addr_t start, phys_addr_t end)
{
unsigned long vaddr;
unsigned int npages;
if (!cc_platform_has(CC_ATTR_GUEST_SEV_SNP))
return;
vaddr = (unsigned long)__va(start);
npages = (end - start) >> PAGE_SHIFT;
set_pages_state(vaddr, npages, SNP_PAGE_STATE_PRIVATE);
}
static int snp_set_vmsa(void *va, bool vmsa)
{
u64 attrs;