[PATCH] irqchip/gic-v3-its: Mark some in-memory data structures as 'decrypted'

[Will Deacon]

The GICv3 ITS driver allocates memory for its tables using alloc_pages()
and performs explicit cache maintenance if necessary. On systems such
as those running pKVM, where the memory encryption API is implemented,
memory shared with the ITS must first be transitioned to the "decrypted"
state, as it would be if allocated via the DMA API.

Allow pKVM guests to interact with an ITS emulation by ensuring that the
shared pages are decrypted at the point of allocation and encrypted
again upon free().

Cc: Thomas Gleixner <tglx at linutronix.de>
Cc: Marc Zyngier <maz at kernel.org>
Signed-off-by: Will Deacon <will at kernel.org>
---

Although pKVM doesn't yet expose share/unshare hypercalls to the guest,
this change is agnostic of the hypervisor and could be queued
independently as it has no functional impact when the memory encryption
API is not implemented.

 drivers/irqchip/irq-gic-v3-its.c | 40 ++++++++++++++++++++++++++------
 1 file changed, 33 insertions(+), 7 deletions(-)

diff --git a/drivers/irqchip/irq-gic-v3-its.c b/drivers/irqchip/irq-gic-v3-its.c
index eb0882d15366..4559b8dfb9bc 100644
--- a/drivers/irqchip/irq-gic-v3-its.c
+++ b/drivers/irqchip/irq-gic-v3-its.c
@@ -27,6 +27,7 @@
 #include <linux/of_pci.h>
 #include <linux/of_platform.h>
 #include <linux/percpu.h>
+#include <linux/set_memory.h>
 #include <linux/slab.h>
 #include <linux/syscore_ops.h>
 
@@ -2166,6 +2167,7 @@ static void gic_reset_prop_table(void *va)
 
 	/* Make sure the GIC will observe the written configuration */
 	gic_flush_dcache_to_poc(va, LPI_PROPBASE_SZ);
+	set_memory_decrypted((unsigned long)va, LPI_PROPBASE_SZ >> PAGE_SHIFT);
 }
 
 static struct page *its_allocate_prop_table(gfp_t gfp_flags)
@@ -2183,8 +2185,10 @@ static struct page *its_allocate_prop_table(gfp_t gfp_flags)
 
 static void its_free_prop_table(struct page *prop_page)
 {
-	free_pages((unsigned long)page_address(prop_page),
-		   get_order(LPI_PROPBASE_SZ));
+	unsigned long va = (unsigned long)page_address(prop_page);
+
+	set_memory_encrypted(va, LPI_PROPBASE_SZ >> PAGE_SHIFT);
+	free_pages(va, get_order(LPI_PROPBASE_SZ));
 }
 
 static bool gic_check_reserved_range(phys_addr_t addr, unsigned long size)
@@ -2377,6 +2381,8 @@ static int its_setup_baser(struct its_node *its, struct its_baser *baser,
 		return -ENXIO;
 	}
 
+	set_memory_decrypted((unsigned long)base,
+			     PAGE_ORDER_TO_SIZE(order) >> PAGE_SHIFT);
 	baser->order = order;
 	baser->base = base;
 	baser->psz = psz;
@@ -2512,8 +2518,12 @@ static void its_free_tables(struct its_node *its)
 
 	for (i = 0; i < GITS_BASER_NR_REGS; i++) {
 		if (its->tables[i].base) {
-			free_pages((unsigned long)its->tables[i].base,
-				   its->tables[i].order);
+			unsigned long base = (unsigned long)its->tables[i].base;
+			u32 order = its->tables[i].order;
+			u32 npages = PAGE_ORDER_TO_SIZE(order) >> PAGE_SHIFT;
+
+			set_memory_encrypted(base, npages);
+			free_pages(base, order);
 			its->tables[i].base = NULL;
 		}
 	}
@@ -2934,6 +2944,7 @@ static int its_alloc_collections(struct its_node *its)
 static struct page *its_allocate_pending_table(gfp_t gfp_flags)
 {
 	struct page *pend_page;
+	void *va;
 
 	pend_page = alloc_pages(gfp_flags | __GFP_ZERO,
 				get_order(LPI_PENDBASE_SZ));
@@ -2941,14 +2952,19 @@ static struct page *its_allocate_pending_table(gfp_t gfp_flags)
 		return NULL;
 
 	/* Make sure the GIC will observe the zero-ed page */
-	gic_flush_dcache_to_poc(page_address(pend_page), LPI_PENDBASE_SZ);
+	va = page_address(pend_page);
+	gic_flush_dcache_to_poc(va, LPI_PENDBASE_SZ);
+	set_memory_decrypted((unsigned long)va, LPI_PENDBASE_SZ >> PAGE_SHIFT);
 
 	return pend_page;
 }
 
 static void its_free_pending_table(struct page *pt)
 {
-	free_pages((unsigned long)page_address(pt), get_order(LPI_PENDBASE_SZ));
+	unsigned long va = (unsigned long)page_address(pt);
+
+	set_memory_encrypted(va, LPI_PENDBASE_SZ >> PAGE_SHIFT);
+	free_pages(va, get_order(LPI_PENDBASE_SZ));
 }
 
 /*
@@ -3268,14 +3284,20 @@ static bool its_alloc_table_entry(struct its_node *its,
 
 	/* Allocate memory for 2nd level table */
 	if (!table[idx]) {
+		void *l2addr;
+
 		page = alloc_pages_node(its->numa_node, GFP_KERNEL | __GFP_ZERO,
 					get_order(baser->psz));
 		if (!page)
 			return false;
 
+		l2addr = page_address(page);
+		set_memory_decrypted((unsigned long)l2addr,
+				     baser->psz >> PAGE_SHIFT);
+
 		/* Flush Lvl2 table to PoC if hw doesn't support coherency */
 		if (!(baser->val & GITS_BASER_SHAREABILITY_MASK))
-			gic_flush_dcache_to_poc(page_address(page), baser->psz);
+			gic_flush_dcache_to_poc(l2addr, baser->psz);
 
 		table[idx] = cpu_to_le64(page_to_phys(page) | GITS_BASER_VALID);
 
@@ -5043,6 +5065,8 @@ static int __init its_probe_one(struct resource *res,
 	its->fwnode_handle = handle;
 	its->get_msi_base = its_irq_get_msi_base;
 	its->msi_domain_flags = IRQ_DOMAIN_FLAG_MSI_REMAP;
+	set_memory_decrypted((unsigned long)its->cmd_base,
+			     ITS_CMD_QUEUE_SZ >> PAGE_SHIFT);
 
 	its_enable_quirks(its);
 
@@ -5099,6 +5123,8 @@ static int __init its_probe_one(struct resource *res,
 out_free_tables:
 	its_free_tables(its);
 out_free_cmd:
+	set_memory_encrypted((unsigned long)its->cmd_base,
+			     ITS_CMD_QUEUE_SZ >> PAGE_SHIFT);
 	free_pages((unsigned long)its->cmd_base, get_order(ITS_CMD_QUEUE_SZ));
 out_unmap_sgir:
 	if (its->sgir_base)
-- 
2.34.1.400.ga245620fadb-goog