Re: [PATCH RFC v7 25/64] crypto: ccp: Add support to initialize the AMD-SP for SEV-SNP

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Hello Jarkko,

On 12/31/2022 9:32 AM, Jarkko Sakkinen wrote:
On Wed, Dec 14, 2022 at 01:40:17PM -0600, Michael Roth wrote:
From: Brijesh Singh <brijesh.singh@xxxxxxx>

Before SNP VMs can be launched, the platform must be appropriately
configured and initialized. Platform initialization is accomplished via
the SNP_INIT command. Make sure to do a WBINVD and issue DF_FLUSH
command to prepare for the first SNP guest launch after INIT.

During the execution of SNP_INIT command, the firmware configures
and enables SNP security policy enforcement in many system components.
Some system components write to regions of memory reserved by early
x86 firmware (e.g. UEFI). Other system components write to regions
provided by the operation system, hypervisor, or x86 firmware.
Such system components can only write to HV-fixed pages or Default
pages. They will error when attempting to write to other page states
after SNP_INIT enables their SNP enforcement.

Starting in SNP firmware v1.52, the SNP_INIT_EX command takes a list of
system physical address ranges to convert into the HV-fixed page states
during the RMP initialization. If INIT_RMP is 1, hypervisors should
provide all system physical address ranges that the hypervisor will
never assign to a guest until the next RMP re-initialization.
For instance, the memory that UEFI reserves should be included in the
range list. This allows system components that occasionally write to
memory (e.g. logging to UEFI reserved regions) to not fail due to
RMP initialization and SNP enablement.

Co-developed-by: Ashish Kalra <ashish.kalra@xxxxxxx>
Signed-off-by: Ashish Kalra <ashish.kalra@xxxxxxx>
Signed-off-by: Brijesh Singh <brijesh.singh@xxxxxxx>
Signed-off-by: Michael Roth <michael.roth@xxxxxxx>
---
  drivers/crypto/ccp/sev-dev.c | 225 +++++++++++++++++++++++++++++++++++
  drivers/crypto/ccp/sev-dev.h |   2 +
  include/linux/psp-sev.h      |  17 +++
  3 files changed, 244 insertions(+)

diff --git a/drivers/crypto/ccp/sev-dev.c b/drivers/crypto/ccp/sev-dev.c
index 9d84720a41d7..af20420bd6c2 100644
--- a/drivers/crypto/ccp/sev-dev.c
+++ b/drivers/crypto/ccp/sev-dev.c
@@ -26,6 +26,7 @@
  #include <linux/fs_struct.h>
#include <asm/smp.h>
+#include <asm/e820/types.h>
#include "psp-dev.h"
  #include "sev-dev.h"
@@ -34,6 +35,10 @@
  #define SEV_FW_FILE		"amd/sev.fw"
  #define SEV_FW_NAME_SIZE	64
+/* Minimum firmware version required for the SEV-SNP support */
+#define SNP_MIN_API_MAJOR	1
+#define SNP_MIN_API_MINOR	51
+
  static DEFINE_MUTEX(sev_cmd_mutex);
  static struct sev_misc_dev *misc_dev;
@@ -76,6 +81,13 @@ static void *sev_es_tmr;
  #define NV_LENGTH (32 * 1024)
  static void *sev_init_ex_buffer;
+/*
+ * SEV_DATA_RANGE_LIST:
+ *   Array containing range of pages that firmware transitions to HV-fixed
+ *   page state.
+ */
+struct sev_data_range_list *snp_range_list;
+
  static inline bool sev_version_greater_or_equal(u8 maj, u8 min)
  {
  	struct sev_device *sev = psp_master->sev_data;
@@ -830,6 +842,186 @@ static int sev_update_firmware(struct device *dev)
  	return ret;
  }
+static void snp_set_hsave_pa(void *arg)
+{
+	wrmsrl(MSR_VM_HSAVE_PA, 0);
+}
+
+static int snp_filter_reserved_mem_regions(struct resource *rs, void *arg)
+{
+	struct sev_data_range_list *range_list = arg;
+	struct sev_data_range *range = &range_list->ranges[range_list->num_elements];
+	size_t size;
+
+	if ((range_list->num_elements * sizeof(struct sev_data_range) +
+	     sizeof(struct sev_data_range_list)) > PAGE_SIZE)
+		return -E2BIG;
+
+	switch (rs->desc) {
+	case E820_TYPE_RESERVED:
+	case E820_TYPE_PMEM:
+	case E820_TYPE_ACPI:
+		range->base = rs->start & PAGE_MASK;
+		size = (rs->end + 1) - rs->start;
+		range->page_count = size >> PAGE_SHIFT;
+		range_list->num_elements++;
+		break;
+	default:
+		break;
+	}
+
+	return 0;
+}
+
+static int __sev_snp_init_locked(int *error)
+{
+	struct psp_device *psp = psp_master;
+	struct sev_data_snp_init_ex data;
+	struct sev_device *sev;
+	int rc = 0;
+
+	if (!psp || !psp->sev_data)
+		return -ENODEV;
+
+	sev = psp->sev_data;
+
+	if (sev->snp_initialized)
+		return 0;

Shouldn't this follow this check:

         if (sev->state == SEV_STATE_INIT) {
                 /* debug printk about possible incorrect call order */
                 return -ENODEV;
         }

It is game over for SNP, if SEV_CMD_INIT{_EX} got first, which means that
this should not proceed.


But, how will SEV_CMD_INIT_EX happen before as sev_pci_init() which is invoked during CCP module load/initialization, will first try to do sev_snp_init() if SNP is supported, before it invokes sev_platform_init() to do SEV firmware initialization ?

Thanks,
Ashish




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