[PATCH Part2 v5 14/45] crypto: ccp: Handle the legacy TMR allocation when SNP is enabled

Brijesh Singh
2021-08-20T16:00:43Z

The behavior and requirement for the SEV-legacy command is altered when
the SNP firmware is in the INIT state. See SEV-SNP firmware specification
for more details.

Allocate the Trusted Memory Region (TMR) as a 2mb sized/aligned region
when SNP is enabled to satify new requirements for the SNP. Continue
allocating a 1mb region for !SNP configuration.

While at it, provide API that can be used by others to allocate a page
that can be used by the firmware. The immediate user for this API will
be the KVM driver. The KVM driver to need to allocate a firmware context
page during the guest creation. The context page need to be updated
by the firmware. See the SEV-SNP specification for further details.

Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
---
drivers/crypto/ccp/sev-dev.c | 169 ++++++++++++++++++++++++++++++++++-
include/linux/psp-sev.h | 11 +++
2 files changed, 176 insertions(+), 4 deletions(-)

diff --git a/drivers/crypto/ccp/sev-dev.c b/drivers/crypto/ccp/sev-dev.c
index 01edad9116f2..34dc358b13b9 100644
--- a/drivers/crypto/ccp/sev-dev.c
+++ b/drivers/crypto/ccp/sev-dev.c
@@ -62,6 +62,14 @@ static int psp_timeout;
#define SEV_ES_TMR_SIZE (1024 * 1024)
static void *sev_es_tmr;

+/* When SEV-SNP is enabled the TMR needs to be 2MB aligned and 2MB size. */
+#define SEV_SNP_ES_TMR_SIZE (2 * 1024 * 1024)
+
+static size_t sev_es_tmr_size = SEV_ES_TMR_SIZE;
+
+static int __sev_do_cmd_locked(int cmd, void *data, int *psp_ret);
+static int sev_do_cmd(int cmd, void *data, int *psp_ret);
+
static inline bool sev_version_greater_or_equal(u8 maj, u8 min)
{
struct sev_device *sev = psp_master->sev_data;
@@ -159,6 +167,156 @@ static int sev_cmd_buffer_len(int cmd)
return 0;
}

+static void snp_leak_pages(unsigned long pfn, unsigned int npages)
+{
+ WARN(1, "psc failed, pfn 0x%lx pages %d (leaking)\n", pfn, npages);
+ while (npages--) {
+ memory_failure(pfn, 0);
+ dump_rmpentry(pfn);
+ pfn++;
+ }
+}
+
+static int snp_reclaim_pages(unsigned long pfn, unsigned int npages, bool locked)
+{
+ struct sev_data_snp_page_reclaim data;
+ int ret, err, i, n = 0;
+
+ for (i = 0; i < npages; i++) {
+ memset(&data, 0, sizeof(data));
+ data.paddr = pfn << PAGE_SHIFT;
+
+ if (locked)
+ ret = __sev_do_cmd_locked(SEV_CMD_SNP_PAGE_RECLAIM, &data, &err);
+ else
+ ret = sev_do_cmd(SEV_CMD_SNP_PAGE_RECLAIM, &data, &err);
+ if (ret)
+ goto cleanup;
+
+ ret = rmp_make_shared(pfn, PG_LEVEL_4K);
+ if (ret)
+ goto cleanup;
+
+ pfn++;
+ n++;
+ }
+
+ return 0;
+
+cleanup:
+ /*
+ * If failed to reclaim the page then page is no longer safe to
+ * be released, leak it.
+ */
+ snp_leak_pages(pfn, npages - n);
+ return ret;
+}
+
+static inline int rmp_make_firmware(unsigned long pfn, int level)
+{
+ return rmp_make_private(pfn, 0, level, 0, true);
+}
+
+static int snp_set_rmp_state(unsigned long paddr, unsigned int npages, bool to_fw, bool locked,
+ bool need_reclaim)
+{
+ unsigned long pfn = __sme_clr(paddr) >> PAGE_SHIFT; /* Cbit maybe set in the paddr */
+ int rc, n = 0, i;
+
+ for (i = 0; i < npages; i++) {
+ if (to_fw)
+ rc = rmp_make_firmware(pfn, PG_LEVEL_4K);
+ else
+ rc = need_reclaim ? snp_reclaim_pages(pfn, 1, locked) :
+ rmp_make_shared(pfn, PG_LEVEL_4K);
+ if (rc)
+ goto cleanup;
+
+ pfn++;
+ n++;
+ }
+
+ return 0;
+
+cleanup:
+ /* Try unrolling the firmware state changes */
+ if (to_fw) {
+ /*
+ * Reclaim the pages which were already changed to the
+ * firmware state.
+ */
+ snp_reclaim_pages(paddr >> PAGE_SHIFT, n, locked);
+
+ return rc;
+ }
+
+ /*
+ * If failed to change the page state to shared, then its not safe
+ * to release the page back to the system, leak it.
+ */
+ snp_leak_pages(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;
+ struct sev_device *sev;
+ struct page *page;
+
+ if (!psp_master || !psp_master->sev_data)
+ return ERR_PTR(-EINVAL);
+
+ page = alloc_pages(gfp_mask, order);
+ if (!page)
+ return NULL;
+
+ /* If SEV-SNP is initialized then add the page in RMP table. */
+ sev = psp_master->sev_data;
+ if (!sev->snp_inited)
+ return page;
+
+ paddr = __pa((unsigned long)page_address(page));
+ if (snp_set_rmp_state(paddr, npages, true, locked, false))
+ return NULL;
+
+ return page;
+}
+
+void *snp_alloc_firmware_page(gfp_t gfp_mask)
+{
+ struct page *page;
+
+ page = __snp_alloc_firmware_pages(gfp_mask, 0, false);
+
+ return page ? page_address(page) : NULL;
+}
+EXPORT_SYMBOL_GPL(snp_alloc_firmware_page);
+
+static void __snp_free_firmware_pages(struct page *page, int order, bool locked)
+{
+ unsigned long paddr, npages = 1ul << order;
+
+ if (!page)
+ return;
+
+ paddr = __pa((unsigned long)page_address(page));
+ if (snp_set_rmp_state(paddr, npages, false, locked, true))
+ return;
+
+ __free_pages(page, order);
+}
+
+void snp_free_firmware_page(void *addr)
+{
+ if (!addr)
+ return;
+
+ __snp_free_firmware_pages(virt_to_page(addr), 0, false);
+}
+EXPORT_SYMBOL(snp_free_firmware_page);
+
static int __sev_do_cmd_locked(int cmd, void *data, int *psp_ret)
{
struct psp_device *psp = psp_master;
@@ -281,7 +439,7 @@ static int __sev_platform_init_locked(int *error)

data.flags |= SEV_INIT_FLAGS_SEV_ES;
data.tmr_address = tmr_pa;
- data.tmr_len = SEV_ES_TMR_SIZE;
+ data.tmr_len = sev_es_tmr_size;
}

rc = __sev_do_cmd_locked(SEV_CMD_INIT, &data, error);
@@ -638,6 +796,8 @@ static int __sev_snp_init_locked(int *error)
sev->snp_inited = true;
dev_dbg(sev->dev, "SEV-SNP firmware initialized\n");

+ sev_es_tmr_size = SEV_SNP_ES_TMR_SIZE;
+
return rc;
}

@@ -1161,8 +1321,9 @@ static void sev_firmware_shutdown(struct sev_device *sev)
/* The TMR area was encrypted, flush it from the cache */
wbinvd_on_all_cpus();

- free_pages((unsigned long)sev_es_tmr,
- get_order(SEV_ES_TMR_SIZE));
+ __snp_free_firmware_pages(virt_to_page(sev_es_tmr),
+ get_order(sev_es_tmr_size),
+ false);
sev_es_tmr = NULL;
}

@@ -1233,7 +1394,7 @@ void sev_pci_init(void)
}

/* Obtain the TMR memory area for SEV-ES use */
- tmr_page = alloc_pages(GFP_KERNEL, get_order(SEV_ES_TMR_SIZE));
+ tmr_page = __snp_alloc_firmware_pages(GFP_KERNEL, get_order(sev_es_tmr_size), false);
if (tmr_page) {
sev_es_tmr = page_address(tmr_page);
} else {
diff --git a/include/linux/psp-sev.h b/include/linux/psp-sev.h
index f2105a8755f9..00bd684dc094 100644
--- a/include/linux/psp-sev.h
+++ b/include/linux/psp-sev.h
@@ -12,6 +12,8 @@
#ifndef __PSP_SEV_H__
#define __PSP_SEV_H__

+#include <linux/sev.h>
+
#include <uapi/linux/psp-sev.h>

#ifdef CONFIG_X86
@@ -919,6 +921,8 @@ int snp_guest_page_reclaim(struct sev_data_snp_page_reclaim *data, int *error);
int snp_guest_dbg_decrypt(struct sev_data_snp_dbg *data, int *error);

void *psp_copy_user_blob(u64 uaddr, u32 len);
+void *snp_alloc_firmware_page(gfp_t mask);
+void snp_free_firmware_page(void *addr);

#else /* !CONFIG_CRYPTO_DEV_SP_PSP */

@@ -960,6 +964,13 @@ static inline int snp_guest_dbg_decrypt(struct sev_data_snp_dbg *data, int *erro
return -ENODEV;
}

+static inline void *snp_alloc_firmware_page(gfp_t mask)
+{
+ return NULL;
+}
+
+static inline void snp_free_firmware_page(void *addr) { }
+
#endif /* CONFIG_CRYPTO_DEV_SP_PSP */

#endif /* __PSP_SEV_H__ */
--
2.17.1