[PATCH RFC v9 47/51] iommu/amd: Add IOMMU_SNP_SHUTDOWN support

Michael Roth
2023-06-12T04:55:33Z

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 | 55 ++++++++++++++++++++++++++++++++++++
include/linux/amd-iommu.h | 1 +
3 files changed, 76 insertions(+)

diff --git a/drivers/crypto/ccp/sev-dev.c b/drivers/crypto/ccp/sev-dev.c
index 0bfe9721c977..b8e8c4da4025 100644
--- a/drivers/crypto/ccp/sev-dev.c
+++ b/drivers/crypto/ccp/sev-dev.c
@@ -24,6 +24,7 @@
#include <linux/cpufeature.h>
#include <linux/fs.h>
#include <linux/fs_struct.h>
+#include <linux/amd-iommu.h>

#include <asm/smp.h>
#include <asm/cacheflush.h>
@@ -1508,6 +1509,25 @@ 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 33ea62d93540..a84ec81cfbb5 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-host.h>

#include <linux/crash_dump.h>

@@ -3701,4 +3702,58 @@ int amd_iommu_snp_enable(void)

return 0;
}
+
+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;
+ 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;
+ }
+
+ amd_iommu_snp_en = false;
+ 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 8f0cde2d451c..7ba46118d0f1 100644
--- a/include/linux/amd-iommu.h
+++ b/include/linux/amd-iommu.h
@@ -208,6 +208,7 @@ struct amd_iommu *get_amd_iommu(unsigned int idx);

#ifdef CONFIG_KVM_AMD_SEV
int amd_iommu_snp_enable(void);
+int amd_iommu_snp_disable(void);
#endif

#endif /* _ASM_X86_AMD_IOMMU_H */
--
2.25.1