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..

See SEV-SNP spec section 5.3.7 for more detail.

Cc: Thomas Gleixner <t...@linutronix.de>
Cc: Ingo Molnar <mi...@redhat.com>
Cc: Borislav Petkov <b...@alien8.de>
Cc: Joerg Roedel <jroe...@suse.de>
Cc: "H. Peter Anvin" <h...@zytor.com>
Cc: Tony Luck <tony.l...@intel.com>
Cc: Dave Hansen <dave.han...@intel.com>
Cc: "Peter Zijlstra (Intel)" <pet...@infradead.org>
Cc: Paolo Bonzini <pbonz...@redhat.com>
Cc: Tom Lendacky <thomas.lenda...@amd.com>
Cc: David Rientjes <rient...@google.com>
Cc: Sean Christopherson <sea...@google.com>
Cc: x...@kernel.org
Cc: k...@vger.kernel.org
Signed-off-by: Brijesh Singh <brijesh.si...@amd.com>
---
 drivers/crypto/ccp/sev-dev.c | 90 +++++++++++++++++++++++++++++++++---
 drivers/crypto/ccp/sev-dev.h |  1 +
 2 files changed, 85 insertions(+), 6 deletions(-)

diff --git a/drivers/crypto/ccp/sev-dev.c b/drivers/crypto/ccp/sev-dev.c
index 242c4775eb56..4aa9d4505d71 100644
--- a/drivers/crypto/ccp/sev-dev.c
+++ b/drivers/crypto/ccp/sev-dev.c
@@ -148,12 +148,35 @@ static int sev_cmd_buffer_len(int cmd)
        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:
+               return true;
+       default:
+               return false;
+       }
+}
+
 static int __sev_do_cmd_locked(int cmd, void *data, int *psp_ret)
 {
+       size_t cmd_buf_len = sev_cmd_buffer_len(cmd);
        struct psp_device *psp = psp_master;
        struct sev_device *sev;
        unsigned int phys_lsb, phys_msb;
        unsigned int reg, ret = 0;
+       struct page *cmd_page = NULL;
+       struct rmpupdate e = {};
 
        if (!psp || !psp->sev_data)
                return -ENODEV;
@@ -163,15 +186,47 @@ static int __sev_do_cmd_locked(int cmd, void *data, int 
*psp_ret)
 
        sev = psp->sev_data;
 
+       /*
+        * Check If SNP is initialized and we are asked to execute a legacy
+        * command that requires write by the firmware in the command buffer.
+        * In that case use an intermediate command buffer page to complete the
+        * operation.
+        *
+        * NOTE: If the command buffer contains a pointer which will be modified
+        * by the firmware then caller must take care of it.
+        */
+       if (sev->snp_inited && sev_legacy_cmd_buf_writable(cmd)) {
+               cmd_page = alloc_page(GFP_KERNEL_ACCOUNT | __GFP_ZERO);
+               if (!cmd_page)
+                       return -ENOMEM;
+
+               memcpy(page_address(cmd_page), data, cmd_buf_len);
+
+               /* make it as a firmware page */
+               e.immutable = true;
+               e.assigned = true;
+               ret = rmptable_rmpupdate(cmd_page, &e);
+               if (ret) {
+                       dev_err(sev->dev, "sev cmd id %#x, failed to change to 
firmware state (spa 0x%lx ret %d).\n",
+                               cmd, page_to_pfn(cmd_page) << PAGE_SHIFT, ret);
+                       goto e_free;
+               }
+       }
+
        /* Get the physical address of the command buffer */
-       phys_lsb = data ? lower_32_bits(__psp_pa(data)) : 0;
-       phys_msb = data ? upper_32_bits(__psp_pa(data)) : 0;
+       if (cmd_page) {
+               phys_lsb = data ? lower_32_bits(__sme_page_pa(cmd_page)) : 0;
+               phys_msb = data ? upper_32_bits(__sme_page_pa(cmd_page)) : 0;
+       } else {
+               phys_lsb = data ? lower_32_bits(__psp_pa(data)) : 0;
+               phys_msb = data ? upper_32_bits(__psp_pa(data)) : 0;
+       }
 
        dev_dbg(sev->dev, "sev command id %#x buffer 0x%08x%08x timeout %us\n",
                cmd, phys_msb, phys_lsb, psp_timeout);
 
        print_hex_dump_debug("(in):  ", DUMP_PREFIX_OFFSET, 16, 2, data,
-                            sev_cmd_buffer_len(cmd), false);
+                            cmd_buf_len, false);
 
        iowrite32(phys_lsb, sev->io_regs + sev->vdata->cmdbuff_addr_lo_reg);
        iowrite32(phys_msb, sev->io_regs + sev->vdata->cmdbuff_addr_hi_reg);
@@ -185,6 +240,24 @@ static int __sev_do_cmd_locked(int cmd, void *data, int 
*psp_ret)
 
        /* wait for command completion */
        ret = sev_wait_cmd_ioc(sev, &reg, psp_timeout);
+
+       /* if an intermediate page is used then copy the data back to original. 
*/
+       if (cmd_page) {
+               int rc;
+
+               /* make it as a hypervisor page */
+               memset(&e, 0, sizeof(struct rmpupdate));
+               rc = rmptable_rmpupdate(cmd_page, &e);
+               if (rc) {
+                       dev_err(sev->dev, "sev cmd id %#x, failed to change to 
hypervisor state ret=%d.\n",
+                               cmd, rc);
+                       /* Set the command page to NULL so that the page is 
leaked. */
+                       cmd_page = NULL;
+               } else {
+                       memcpy(data, page_address(cmd_page), cmd_buf_len);
+               }
+       }
+
        if (ret) {
                if (psp_ret)
                        *psp_ret = 0;
@@ -192,7 +265,7 @@ static int __sev_do_cmd_locked(int cmd, void *data, int 
*psp_ret)
                dev_err(sev->dev, "sev command %#x timed out, disabling PSP\n", 
cmd);
                psp_dead = true;
 
-               return ret;
+               goto e_free;
        }
 
        psp_timeout = psp_cmd_timeout;
@@ -207,8 +280,11 @@ static int __sev_do_cmd_locked(int cmd, void *data, int 
*psp_ret)
        }
 
        print_hex_dump_debug("(out): ", DUMP_PREFIX_OFFSET, 16, 2, data,
-                            sev_cmd_buffer_len(cmd), false);
+                            cmd_buf_len, false);
 
+e_free:
+       if (cmd_page)
+               __free_page(cmd_page);
        return ret;
 }
 
@@ -234,7 +310,7 @@ static int __sev_platform_init_locked(int *error)
 
        sev = psp->sev_data;
 
-       if (sev->state == SEV_STATE_INIT)
+       if (sev->legacy_inited && (sev->state == SEV_STATE_INIT))
                return 0;
 
        if (sev_es_tmr) {
@@ -255,6 +331,7 @@ static int __sev_platform_init_locked(int *error)
        if (rc)
                return rc;
 
+       sev->legacy_inited = true;
        sev->state = SEV_STATE_INIT;
 
        /* Prepare for first SEV guest launch after INIT */
@@ -289,6 +366,7 @@ static int __sev_platform_shutdown_locked(int *error)
        if (ret)
                return ret;
 
+       sev->legacy_inited = false;
        sev->state = SEV_STATE_UNINIT;
        dev_dbg(sev->dev, "SEV firmware shutdown\n");
 
diff --git a/drivers/crypto/ccp/sev-dev.h b/drivers/crypto/ccp/sev-dev.h
index 18b116a817ff..2ee9665a901d 100644
--- a/drivers/crypto/ccp/sev-dev.h
+++ b/drivers/crypto/ccp/sev-dev.h
@@ -54,6 +54,7 @@ struct sev_device {
        u8 build;
 
        bool snp_inited;
+       bool legacy_inited;
 };
 
 int sev_dev_init(struct psp_device *psp);
-- 
2.17.1

Reply via email to