[PATCH RFC v8 56/56] iommu/amd: Add IOMMU_SNP_SHUTDOWN support

[Michael Roth <michael.roth@xxxxxxx>]

From: Ashish Kalra <ashish.kalra@xxxxxxx>

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@xxxxxxx>
Signed-off-by: Michael Roth <michael.roth@xxxxxxx>
---
 drivers/crypto/ccp/sev-dev.c | 20 ++++++++++++++
 drivers/iommu/amd/init.c     | 53 ++++++++++++++++++++++++++++++++++++
 include/linux/amd-iommu.h    |  1 +
 3 files changed, 74 insertions(+)

diff --git a/drivers/crypto/ccp/sev-dev.c b/drivers/crypto/ccp/sev-dev.c
index bf5167b2acfc..7ded2f9111e0 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/e820/types.h>
@@ -1503,6 +1504,25 @@ 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 1a2d425bf568..d1270e3c5baf 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>
 
@@ -3651,4 +3652,56 @@ int amd_iommu_snp_enable(void)
 
 	return 0;
 }
+
+static int iommu_page_make_shared(void *page)
+{
+	unsigned long pfn;
+
+	pfn = iommu_virt_to_phys(page) >> 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 953e6f12fa1c..a1b33b838842 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_AMD_MEM_ENCRYPT
 int amd_iommu_snp_enable(void);
+int amd_iommu_snp_disable(void);
 #endif
 
 #endif /* _ASM_X86_AMD_IOMMU_H */
-- 
2.25.1