[PATCH RFC v8 25/56] crypto: ccp: Handle the legacy SEV command when SNP is enabled

From: Michael Roth
Date: Mon Feb 20 2023 - 13:50:52 EST

From: Brijesh Singh <brijesh.singh@xxxxxxx>

The behavior of the SEV-legacy commands is altered when the SNP firmware
is in the INIT state. When SNP is in INIT state, all the SEV-legacy
commands that cause the firmware to write to memory must be in the
firmware state before issuing the command..

A command buffer may contains a system physical address that the firmware
may write to. There are two cases that need to be handled:

1) system physical address points to a guest memory
2) system physical address points to a host memory

To handle the case #1, change the page state to the firmware in the RMP
table before issuing the command and restore the state to shared after the
command completes.

For the case #2, use a bounce buffer to complete the request.

Signed-off-by: Brijesh Singh <brijesh.singh@xxxxxxx>
Signed-off-by: Ashish Kalra <ashish.kalra@xxxxxxx>
Signed-off-by: Michael Roth <michael.roth@xxxxxxx>
---
drivers/crypto/ccp/sev-dev.c | 371 ++++++++++++++++++++++++++++++++++-
drivers/crypto/ccp/sev-dev.h | 12 ++
2 files changed, 373 insertions(+), 10 deletions(-)

diff --git a/drivers/crypto/ccp/sev-dev.c b/drivers/crypto/ccp/sev-dev.c
index 4c12e98a1219..fd8893af6ed7 100644
--- a/drivers/crypto/ccp/sev-dev.c
+++ b/drivers/crypto/ccp/sev-dev.c
@@ -27,6 +27,7 @@

#include <asm/smp.h>
#include <asm/e820/types.h>
+#include <asm/sev.h>

#include "psp-dev.h"
#include "sev-dev.h"
@@ -286,6 +287,30 @@ static int rmp_mark_pages_firmware(unsigned long paddr, unsigned int npages, boo
return rc;
}

+static int rmp_mark_pages_shared(unsigned long paddr, unsigned int npages)
+{
+ /* Cbit maybe set in the paddr */
+ unsigned long pfn = __sme_clr(paddr) >> PAGE_SHIFT;
+ int rc, n = 0, i;
+
+ for (i = 0; i < npages; i++, pfn++, n++) {
+ rc = rmp_make_shared(pfn, PG_LEVEL_4K);
+ if (rc)
+ goto cleanup;
+ }
+
+ return 0;
+
+cleanup:
+ /*
+ * If failed to change the page state to shared, then its not safe
+ * to release the page back to the system, leak it.
+ */
+ snp_mark_pages_offline(pfn, npages - n);
+
+ return rc;
+}
+
static struct page *__snp_alloc_firmware_pages(gfp_t gfp_mask, int order, bool locked)
{
unsigned long npages = 1ul << order, paddr;
@@ -487,12 +512,295 @@ static int sev_write_init_ex_file_if_required(int cmd_id)
return sev_write_init_ex_file();
}

+static int alloc_snp_host_map(struct sev_device *sev)
+{
+ struct page *page;
+ int i;
+
+ for (i = 0; i < MAX_SNP_HOST_MAP_BUFS; i++) {
+ struct snp_host_map *map = &sev->snp_host_map[i];
+
+ memset(map, 0, sizeof(*map));
+
+ page = alloc_pages(GFP_KERNEL_ACCOUNT, get_order(SEV_FW_BLOB_MAX_SIZE));
+ if (!page)
+ return -ENOMEM;
+
+ map->host = page_address(page);
+ }
+
+ return 0;
+}
+
+static void free_snp_host_map(struct sev_device *sev)
+{
+ int i;
+
+ for (i = 0; i < MAX_SNP_HOST_MAP_BUFS; i++) {
+ struct snp_host_map *map = &sev->snp_host_map[i];
+
+ if (map->host) {
+ __free_pages(virt_to_page(map->host), get_order(SEV_FW_BLOB_MAX_SIZE));
+ memset(map, 0, sizeof(*map));
+ }
+ }
+}
+
+static int map_firmware_writeable(u64 *paddr, u32 len, bool guest, struct snp_host_map *map)
+{
+ unsigned int npages = PAGE_ALIGN(len) >> PAGE_SHIFT;
+
+ map->active = false;
+
+ if (!paddr || !len)
+ return 0;
+
+ map->paddr = *paddr;
+ map->len = len;
+
+ /* If paddr points to a guest memory then change the page state to firmwware. */
+ if (guest) {
+ if (rmp_mark_pages_firmware(*paddr, npages, true))
+ return -EFAULT;
+
+ goto done;
+ }
+
+ if (!map->host)
+ return -ENOMEM;
+
+ /* Check if the pre-allocated buffer can be used to fullfil the request. */
+ if (len > SEV_FW_BLOB_MAX_SIZE)
+ return -EINVAL;
+
+ /* Transition the pre-allocated buffer to the firmware state. */
+ if (rmp_mark_pages_firmware(__pa(map->host), npages, true))
+ return -EFAULT;
+
+ /* Set the paddr to use pre-allocated firmware buffer */
+ *paddr = __psp_pa(map->host);
+
+done:
+ map->active = true;
+ return 0;
+}
+
+static int unmap_firmware_writeable(u64 *paddr, u32 len, bool guest, struct snp_host_map *map)
+{
+ unsigned int npages = PAGE_ALIGN(len) >> PAGE_SHIFT;
+
+ if (!map->active)
+ return 0;
+
+ /* If paddr points to a guest memory then restore the page state to hypervisor. */
+ if (guest) {
+ if (snp_reclaim_pages(*paddr, npages, true))
+ return -EFAULT;
+
+ goto done;
+ }
+
+ /*
+ * Transition the pre-allocated buffer to hypervisor state before the access.
+ *
+ * This is because while changing the page state to firmware, the kernel unmaps
+ * the pages from the direct map, and to restore the direct map the pages must
+ * be transitioned back to the shared state.
+ */
+ if (snp_reclaim_pages(__pa(map->host), npages, true))
+ return -EFAULT;
+
+ /* Copy the response data firmware buffer to the callers buffer. */
+ memcpy(__va(__sme_clr(map->paddr)), map->host, min_t(size_t, len, map->len));
+ *paddr = map->paddr;
+
+done:
+ map->active = false;
+ return 0;
+}
+
+static bool sev_legacy_cmd_buf_writable(int cmd)
+{
+ switch (cmd) {
+ case SEV_CMD_PLATFORM_STATUS:
+ case SEV_CMD_GUEST_STATUS:
+ case SEV_CMD_LAUNCH_START:
+ case SEV_CMD_RECEIVE_START:
+ case SEV_CMD_LAUNCH_MEASURE:
+ case SEV_CMD_SEND_START:
+ case SEV_CMD_SEND_UPDATE_DATA:
+ case SEV_CMD_SEND_UPDATE_VMSA:
+ case SEV_CMD_PEK_CSR:
+ case SEV_CMD_PDH_CERT_EXPORT:
+ case SEV_CMD_GET_ID:
+ case SEV_CMD_ATTESTATION_REPORT:
+ return true;
+ default:
+ return false;
+ }
+}
+
+#define prep_buffer(name, addr, len, guest, map) \
+ func(&((typeof(name *))cmd_buf)->addr, ((typeof(name *))cmd_buf)->len, guest, map)
+
+static int __snp_cmd_buf_copy(int cmd, void *cmd_buf, bool to_fw, int fw_err)
+{
+ int (*func)(u64 *paddr, u32 len, bool guest, struct snp_host_map *map);
+ struct sev_device *sev = psp_master->sev_data;
+ bool from_fw = !to_fw;
+
+ /*
+ * After the command is completed, change the command buffer memory to
+ * hypervisor state.
+ *
+ * The immutable bit is automatically cleared by the firmware, so
+ * no not need to reclaim the page.
+ */
+ if (from_fw && sev_legacy_cmd_buf_writable(cmd)) {
+ if (rmp_mark_pages_shared(__pa(cmd_buf), 1))
+ return -EFAULT;
+
+ /* No need to go further if firmware failed to execute command. */
+ if (fw_err)
+ return 0;
+ }
+
+ if (to_fw)
+ func = map_firmware_writeable;
+ else
+ func = unmap_firmware_writeable;
+
+ /*
+ * A command buffer may contains a system physical address. If the address
+ * points to a host memory then use an intermediate firmware page otherwise
+ * change the page state in the RMP table.
+ */
+ switch (cmd) {
+ case SEV_CMD_PDH_CERT_EXPORT:
+ if (prep_buffer(struct sev_data_pdh_cert_export, pdh_cert_address,
+ pdh_cert_len, false, &sev->snp_host_map[0]))
+ goto err;
+ if (prep_buffer(struct sev_data_pdh_cert_export, cert_chain_address,
+ cert_chain_len, false, &sev->snp_host_map[1]))
+ goto err;
+ break;
+ case SEV_CMD_GET_ID:
+ if (prep_buffer(struct sev_data_get_id, address, len,
+ false, &sev->snp_host_map[0]))
+ goto err;
+ break;
+ case SEV_CMD_PEK_CSR:
+ if (prep_buffer(struct sev_data_pek_csr, address, len,
+ false, &sev->snp_host_map[0]))
+ goto err;
+ break;
+ case SEV_CMD_LAUNCH_UPDATE_DATA:
+ if (prep_buffer(struct sev_data_launch_update_data, address, len,
+ true, &sev->snp_host_map[0]))
+ goto err;
+ break;
+ case SEV_CMD_LAUNCH_UPDATE_VMSA:
+ if (prep_buffer(struct sev_data_launch_update_vmsa, address, len,
+ true, &sev->snp_host_map[0]))
+ goto err;
+ break;
+ case SEV_CMD_LAUNCH_MEASURE:
+ if (prep_buffer(struct sev_data_launch_measure, address, len,
+ false, &sev->snp_host_map[0]))
+ goto err;
+ break;
+ case SEV_CMD_LAUNCH_UPDATE_SECRET:
+ if (prep_buffer(struct sev_data_launch_secret, guest_address, guest_len,
+ true, &sev->snp_host_map[0]))
+ goto err;
+ break;
+ case SEV_CMD_DBG_DECRYPT:
+ if (prep_buffer(struct sev_data_dbg, dst_addr, len, false,
+ &sev->snp_host_map[0]))
+ goto err;
+ break;
+ case SEV_CMD_DBG_ENCRYPT:
+ if (prep_buffer(struct sev_data_dbg, dst_addr, len, true,
+ &sev->snp_host_map[0]))
+ goto err;
+ break;
+ case SEV_CMD_ATTESTATION_REPORT:
+ if (prep_buffer(struct sev_data_attestation_report, address, len,
+ false, &sev->snp_host_map[0]))
+ goto err;
+ break;
+ case SEV_CMD_SEND_START:
+ if (prep_buffer(struct sev_data_send_start, session_address,
+ session_len, false, &sev->snp_host_map[0]))
+ goto err;
+ break;
+ case SEV_CMD_SEND_UPDATE_DATA:
+ if (prep_buffer(struct sev_data_send_update_data, hdr_address, hdr_len,
+ false, &sev->snp_host_map[0]))
+ goto err;
+ if (prep_buffer(struct sev_data_send_update_data, trans_address,
+ trans_len, false, &sev->snp_host_map[1]))
+ goto err;
+ break;
+ case SEV_CMD_SEND_UPDATE_VMSA:
+ if (prep_buffer(struct sev_data_send_update_vmsa, hdr_address, hdr_len,
+ false, &sev->snp_host_map[0]))
+ goto err;
+ if (prep_buffer(struct sev_data_send_update_vmsa, trans_address,
+ trans_len, false, &sev->snp_host_map[1]))
+ goto err;
+ break;
+ case SEV_CMD_RECEIVE_UPDATE_DATA:
+ if (prep_buffer(struct sev_data_receive_update_data, guest_address,
+ guest_len, true, &sev->snp_host_map[0]))
+ goto err;
+ break;
+ case SEV_CMD_RECEIVE_UPDATE_VMSA:
+ if (prep_buffer(struct sev_data_receive_update_vmsa, guest_address,
+ guest_len, true, &sev->snp_host_map[0]))
+ goto err;
+ break;
+ default:
+ break;
+ }
+
+ /* The command buffer need to be in the firmware state. */
+ if (to_fw && sev_legacy_cmd_buf_writable(cmd)) {
+ if (rmp_mark_pages_firmware(__pa(cmd_buf), 1, true))
+ return -EFAULT;
+ }
+
+ return 0;
+
+err:
+ return -EINVAL;
+}
+
+static inline bool need_firmware_copy(int cmd)
+{
+ struct sev_device *sev = psp_master->sev_data;
+
+ /* After SNP is INIT'ed, the behavior of legacy SEV command is changed. */
+ return ((cmd < SEV_CMD_SNP_INIT) && sev->snp_initialized) ? true : false;
+}
+
+static int snp_aware_copy_to_firmware(int cmd, void *data)
+{
+ return __snp_cmd_buf_copy(cmd, data, true, 0);
+}
+
+static int snp_aware_copy_from_firmware(int cmd, void *data, int fw_err)
+{
+ return __snp_cmd_buf_copy(cmd, data, false, fw_err);
+}
+
static int __sev_do_cmd_locked(int cmd, void *data, int *psp_ret)
{
struct psp_device *psp = psp_master;
struct sev_device *sev;
unsigned int phys_lsb, phys_msb;
unsigned int reg, ret = 0;
+ void *cmd_buf;
int buf_len;

if (!psp || !psp->sev_data)
@@ -512,12 +820,28 @@ static int __sev_do_cmd_locked(int cmd, void *data, int *psp_ret)
* work for some memory, e.g. vmalloc'd addresses, and @data may not be
* physically contiguous.
*/
- if (data)
- memcpy(sev->cmd_buf, data, buf_len);
+ if (data) {
+ if (sev->cmd_buf_active > 2)
+ return -EBUSY;
+
+ cmd_buf = sev->cmd_buf_active ? sev->cmd_buf_backup : sev->cmd_buf;
+
+ memcpy(cmd_buf, data, buf_len);
+ sev->cmd_buf_active++;
+
+ /*
+ * The behavior of the SEV-legacy commands is altered when the
+ * SNP firmware is in the INIT state.
+ */
+ if (need_firmware_copy(cmd) && snp_aware_copy_to_firmware(cmd, cmd_buf))
+ return -EFAULT;
+ } else {
+ cmd_buf = sev->cmd_buf;
+ }

/* Get the physical address of the command buffer */
- phys_lsb = data ? lower_32_bits(__psp_pa(sev->cmd_buf)) : 0;
- phys_msb = data ? upper_32_bits(__psp_pa(sev->cmd_buf)) : 0;
+ phys_lsb = data ? lower_32_bits(__psp_pa(cmd_buf)) : 0;
+ phys_msb = data ? upper_32_bits(__psp_pa(cmd_buf)) : 0;

dev_dbg(sev->dev, "sev command id %#x buffer 0x%08x%08x timeout %us\n",
cmd, phys_msb, phys_lsb, psp_timeout);
@@ -560,15 +884,24 @@ static int __sev_do_cmd_locked(int cmd, void *data, int *psp_ret)
ret = sev_write_init_ex_file_if_required(cmd);
}

- print_hex_dump_debug("(out): ", DUMP_PREFIX_OFFSET, 16, 2, data,
- buf_len, false);
-
/*
* Copy potential output from the PSP back to data. Do this even on
* failure in case the caller wants to glean something from the error.
*/
- if (data)
- memcpy(data, sev->cmd_buf, buf_len);
+ if (data) {
+ /*
+ * Restore the page state after the command completes.
+ */
+ if (need_firmware_copy(cmd) &&
+ snp_aware_copy_from_firmware(cmd, cmd_buf, ret))
+ return -EFAULT;
+
+ memcpy(data, cmd_buf, buf_len);
+ sev->cmd_buf_active--;
+ }
+
+ print_hex_dump_debug("(out): ", DUMP_PREFIX_OFFSET, 16, 2, data,
+ buf_len, false);

return ret;
}
@@ -1579,10 +1912,12 @@ int sev_dev_init(struct psp_device *psp)
if (!sev)
goto e_err;

- sev->cmd_buf = (void *)devm_get_free_pages(dev, GFP_KERNEL, 0);
+ sev->cmd_buf = (void *)devm_get_free_pages(dev, GFP_KERNEL, 1);
if (!sev->cmd_buf)
goto e_sev;

+ sev->cmd_buf_backup = (uint8_t *)sev->cmd_buf + PAGE_SIZE;
+
psp->sev_data = sev;

sev->dev = dev;
@@ -1648,6 +1983,12 @@ static void sev_firmware_shutdown(struct sev_device *sev)
snp_range_list = NULL;
}

+ /*
+ * The host map need to clear the immutable bit so it must be free'd before the
+ * SNP firmware shutdown.
+ */
+ free_snp_host_map(sev);
+
sev_snp_shutdown(&error);
}

@@ -1722,6 +2063,14 @@ void sev_pci_init(void)
dev_err(sev->dev, "SEV-SNP: failed to INIT error %#x\n", error);
}
}
+
+ /*
+ * Allocate the intermediate buffers used for the legacy command handling.
+ */
+ if (alloc_snp_host_map(sev)) {
+ dev_notice(sev->dev, "Failed to alloc host map (disabling legacy SEV)\n");
+ goto skip_legacy;
+ }
}

/* Obtain the TMR memory area for SEV-ES use */
@@ -1739,12 +2088,14 @@ void sev_pci_init(void)
dev_err(sev->dev, "SEV: failed to INIT error %#x, rc %d\n",
error, rc);

+skip_legacy:
dev_info(sev->dev, "SEV%s API:%d.%d build:%d\n", sev->snp_initialized ?
"-SNP" : "", sev->api_major, sev->api_minor, sev->build);

return;

err:
+ free_snp_host_map(sev);
psp_master->sev_data = NULL;
}

diff --git a/drivers/crypto/ccp/sev-dev.h b/drivers/crypto/ccp/sev-dev.h
index 34767657beb5..19d79f9d4212 100644
--- a/drivers/crypto/ccp/sev-dev.h
+++ b/drivers/crypto/ccp/sev-dev.h
@@ -29,11 +29,20 @@
#define SEV_CMDRESP_CMD_SHIFT 16
#define SEV_CMDRESP_IOC BIT(0)

+#define MAX_SNP_HOST_MAP_BUFS 2
+
struct sev_misc_dev {
struct kref refcount;
struct miscdevice misc;
};

+struct snp_host_map {
+ u64 paddr;
+ u32 len;
+ void *host;
+ bool active;
+};
+
struct sev_device {
struct device *dev;
struct psp_device *psp;
@@ -52,8 +61,11 @@ struct sev_device {
u8 build;

void *cmd_buf;
+ void *cmd_buf_backup;
+ int cmd_buf_active;

bool snp_initialized;
+ struct snp_host_map snp_host_map[MAX_SNP_HOST_MAP_BUFS];
};

int sev_dev_init(struct psp_device *psp);
--
2.25.1