[PATCH v1 19/26] iommu/amd: Clean up RMP entries for IOMMU pages during SNP shutdown

Michael Roth
2023-12-30T16:25:38Z

From: Ashish Kalra <ashish.kalra@amd.com>

Add a new IOMMU API interface amd_iommu_snp_disable() to transition
IOMMU pages to Hypervisor state from Reclaim state after SNP_SHUTDOWN_EX
command. Invoke this API from the CCP driver after SNP_SHUTDOWN_EX
command.

Signed-off-by: Ashish Kalra <ashish.kalra@amd.com>
Signed-off-by: Michael Roth <michael.roth@amd.com>
---
drivers/crypto/ccp/sev-dev.c | 20 +++++++++
drivers/iommu/amd/init.c | 79 ++++++++++++++++++++++++++++++++++++
include/linux/amd-iommu.h | 6 +++
3 files changed, 105 insertions(+)

diff --git a/drivers/crypto/ccp/sev-dev.c b/drivers/crypto/ccp/sev-dev.c
index 8cfb376ca2e7..47fc58ed9e6a 100644
--- a/drivers/crypto/ccp/sev-dev.c
+++ b/drivers/crypto/ccp/sev-dev.c
@@ -26,6 +26,7 @@
#include <linux/fs.h>
#include <linux/fs_struct.h>
#include <linux/psp.h>
+#include <linux/amd-iommu.h>

#include <asm/smp.h>
#include <asm/cacheflush.h>
@@ -1675,6 +1676,25 @@ static int __sev_snp_shutdown_locked(int *error)
return ret;
}

+ /*
+ * SNP_SHUTDOWN_EX with IOMMU_SNP_SHUTDOWN set to 1 disables SNP
+ * enforcement by the IOMMU and also transitions all pages
+ * associated with the IOMMU to the Reclaim state.
+ * Firmware was transitioning the IOMMU pages to Hypervisor state
+ * before version 1.53. But, accounting for the number of assigned
+ * 4kB pages in a 2M page was done incorrectly by not transitioning
+ * to the Reclaim state. This resulted in RMP #PF when later accessing
+ * the 2M page containing those pages during kexec boot. Hence, the
+ * firmware now transitions these pages to Reclaim state and hypervisor
+ * needs to transition these pages to shared state. SNP Firmware
+ * version 1.53 and above are needed for kexec boot.
+ */
+ ret = amd_iommu_snp_disable();
+ if (ret) {
+ dev_err(sev->dev, "SNP IOMMU shutdown failed\n");
+ return ret;
+ }
+
sev->snp_initialized = false;
dev_dbg(sev->dev, "SEV-SNP firmware shutdown\n");

diff --git a/drivers/iommu/amd/init.c b/drivers/iommu/amd/init.c
index 96a1a7fed470..3d95b2e67784 100644
--- a/drivers/iommu/amd/init.c
+++ b/drivers/iommu/amd/init.c
@@ -30,6 +30,7 @@
#include <asm/io_apic.h>
#include <asm/irq_remapping.h>
#include <asm/set_memory.h>
+#include <asm/sev.h>

#include <linux/crash_dump.h>

@@ -3797,3 +3798,81 @@ int amd_iommu_pc_set_reg(struct amd_iommu *iommu, u8 bank, u8 cntr, u8 fxn, u64

return iommu_pc_get_set_reg(iommu, bank, cntr, fxn, value, true);
}
+
+#ifdef CONFIG_KVM_AMD_SEV
+static int iommu_page_make_shared(void *page)
+{
+ unsigned long paddr, pfn;
+
+ paddr = iommu_virt_to_phys(page);
+ /* Cbit maybe set in the paddr */
+ pfn = __sme_clr(paddr) >> PAGE_SHIFT;
+
+ if (!(pfn % PTRS_PER_PMD)) {
+ int ret, level;
+ bool assigned;
+
+ ret = snp_lookup_rmpentry(pfn, &assigned, &level);
+ if (ret)
+ pr_warn("IOMMU PFN %lx RMP lookup failed, ret %d\n",
+ pfn, ret);
+
+ if (!assigned)
+ pr_warn("IOMMU PFN %lx not assigned in RMP table\n",
+ pfn);
+
+ if (level > PG_LEVEL_4K) {
+ ret = psmash(pfn);
+ if (ret) {
+ pr_warn("IOMMU PFN %lx had a huge RMP entry, but attempted psmash failed, ret: %d, level: %d\n",
+ pfn, ret, level);
+ }
+ }
+ }
+
+ return rmp_make_shared(pfn, PG_LEVEL_4K);
+}
+
+static int iommu_make_shared(void *va, size_t size)
+{
+ void *page;
+ int ret;
+
+ if (!va)
+ return 0;
+
+ for (page = va; page < (va + size); page += PAGE_SIZE) {
+ ret = iommu_page_make_shared(page);
+ if (ret)
+ return ret;
+ }
+
+ return 0;
+}
+
+int amd_iommu_snp_disable(void)
+{
+ struct amd_iommu *iommu;
+ int ret;
+
+ if (!amd_iommu_snp_en)
+ return 0;
+
+ for_each_iommu(iommu) {
+ ret = iommu_make_shared(iommu->evt_buf, EVT_BUFFER_SIZE);
+ if (ret)
+ return ret;
+
+ ret = iommu_make_shared(iommu->ppr_log, PPR_LOG_SIZE);
+ if (ret)
+ return ret;
+
+ ret = iommu_make_shared((void *)iommu->cmd_sem, PAGE_SIZE);
+ if (ret)
+ return ret;
+ }
+
+ return 0;
+}
+EXPORT_SYMBOL_GPL(amd_iommu_snp_disable);
+#endif
diff --git a/include/linux/amd-iommu.h b/include/linux/amd-iommu.h
index 7365be00a795..2b90c48a6a87 100644
--- a/include/linux/amd-iommu.h
+++ b/include/linux/amd-iommu.h
@@ -85,4 +85,10 @@ int amd_iommu_pc_get_reg(struct amd_iommu *iommu, u8 bank, u8 cntr, u8 fxn,
u64 *value);
struct amd_iommu *get_amd_iommu(unsigned int idx);

+#ifdef CONFIG_KVM_AMD_SEV
+int amd_iommu_snp_disable(void);
+#else
+static inline int amd_iommu_snp_disable(void) { return 0; }
+#endif
+
#endif /* _ASM_X86_AMD_IOMMU_H */
--
2.25.1