[PATCH 05/14] irqchip/gic-v3-its: Prepare shadow structures for KVM host deprivilege

Sebastian Ene
2026-03-10T12:50:10Z

Expose two helper functions to support emulated ITS in the hypervisor.
These allow the KVM layer to notify the driver when hypervisor
initialization is complete.
The caller is expected to use the functions as follows:
1. its_start_deprivilege(): Acquire the ITS locks.
2. on_each_cpu(_kvm_host_prot_finalize, ...): Finalizes pKVM init
3. its_end_deprivilege(): Shadow the ITS structures, invoke the KVM
callback, and release locks.
Specifically, this shadows the ITS command queue and the 1st level
indirect tables. These shadow buffers will be used by the driver after
host deprivilege, while the hypervisor unmaps and takes ownership of the
original structures.

Signed-off-by: Sebastian Ene <sebastianene@google.com>
---
drivers/irqchip/irq-gic-v3-its.c | 165 +++++++++++++++++++++++++++--
include/linux/irqchip/arm-gic-v3.h | 24 +++++
2 files changed, 178 insertions(+), 11 deletions(-)

diff --git a/drivers/irqchip/irq-gic-v3-its.c b/drivers/irqchip/irq-gic-v3-its.c
index 291d7668cc8d..278dbc56f962 100644
--- a/drivers/irqchip/irq-gic-v3-its.c
+++ b/drivers/irqchip/irq-gic-v3-its.c
@@ -78,17 +78,6 @@ struct its_collection {
u16 col_id;
};

-/*
- * The ITS_BASER structure - contains memory information, cached
- * value of BASER register configuration and ITS page size.
- */
-struct its_baser {
- void *base;
- u64 val;
- u32 order;
- u32 psz;
-};
-
struct its_device;

/*
@@ -5232,6 +5221,160 @@ static int __init its_compute_its_list_map(struct its_node *its)
return its_number;
}

+static void its_free_shadow_tables(struct its_shadow_tables *shadow)
+{
+ int i;
+
+ if (shadow->cmd_shadow)
+ its_free_pages(shadow->cmd_shadow, get_order(ITS_CMD_QUEUE_SZ));
+
+ for (i = 0; i < GITS_BASER_NR_REGS; i++) {
+ if (!shadow->tables[i].shadow)
+ continue;
+
+ its_free_pages(shadow->tables[i].shadow, 0);
+ }
+
+ its_free_pages(shadow, 0);
+}
+
+static struct its_shadow_tables *its_get_shadow_tables(struct its_node *its)
+{
+ void *page;
+ struct its_shadow_tables *shadow;
+ int i;
+
+ page = its_alloc_pages_node(its->numa_node, GFP_KERNEL | __GFP_ZERO, 0);
+ if (!page)
+ return NULL;
+
+ shadow = (void *)page_address(page);
+ page = its_alloc_pages_node(its->numa_node,
+ GFP_KERNEL | __GFP_ZERO,
+ get_order(ITS_CMD_QUEUE_SZ));
+ if (!page)
+ goto err_alloc_shadow;
+
+ shadow->cmd_shadow = page_address(page);
+ shadow->cmdq_len = ITS_CMD_QUEUE_SZ;
+ shadow->cmd_original = its->cmd_base;
+
+ memcpy(shadow->tables, its->tables, sizeof(struct its_baser) * GITS_BASER_NR_REGS);
+
+ for (i = 0; i < GITS_BASER_NR_REGS; i++) {
+ if (!(shadow->tables[i].val & GITS_BASER_VALID))
+ continue;
+
+ if (!(shadow->tables[i].val & GITS_BASER_INDIRECT))
+ continue;
+
+ page = its_alloc_pages_node(its->numa_node,
+ GFP_KERNEL | __GFP_ZERO,
+ shadow->tables[i].order);
+ if (!page)
+ goto err_alloc_shadow;
+
+ shadow->tables[i].shadow = page_address(page);
+
+ memcpy(shadow->tables[i].shadow, shadow->tables[i].base,
+ PAGE_ORDER_TO_SIZE(shadow->tables[i].order));
+ }
+
+ return shadow;
+
+err_alloc_shadow:
+ its_free_shadow_tables(shadow);
+ return NULL;
+}
+
+void *its_start_depriviledge(void)
+{
+ struct its_node *its;
+ int num_nodes = 0, i = 0;
+ unsigned long *flags;
+
+ raw_spin_lock(&its_lock);
+ list_for_each_entry(its, &its_nodes, entry) {
+ num_nodes++;
+ }
+
+ flags = kzalloc(num_nodes * sizeof(unsigned long), GFP_KERNEL_ACCOUNT);
+ if (!flags) {
+ raw_spin_unlock(&its_lock);
+ return NULL;
+ }
+
+ list_for_each_entry(its, &its_nodes, entry) {
+ raw_spin_lock_irqsave(&its->lock, flags[i++]);
+ }
+
+ return flags;
+}
+EXPORT_SYMBOL_GPL(its_start_depriviledge);
+
+static int its_switch_to_shadow_locked(struct its_node *its, its_init_emulate init_emulate_cb)
+{
+ struct its_shadow_tables *hyp_shadow, shadow;
+ int i, ret;
+ u64 baser, baser_phys;
+
+ hyp_shadow = its_get_shadow_tables(its);
+ if (!hyp_shadow)
+ return -ENOMEM;
+
+ memcpy(&shadow, hyp_shadow, sizeof(shadow));
+ ret = init_emulate_cb(its->phys_base, hyp_shadow);
+ if (ret) {
+ its_free_shadow_tables(hyp_shadow);
+ return ret;
+ }
+
+ /* Switch the driver command queue to use the shadow and save the original */
+ its->cmd_write = (its->cmd_write - its->cmd_base) +
+ (struct its_cmd_block *)shadow.cmd_shadow;
+ its->cmd_base = shadow.cmd_shadow;
+
+ /* Shadow the first level of the indirect tables */
+ for (i = 0; i < GITS_BASER_NR_REGS; i++) {
+ baser = shadow.tables[i].val;
+
+ if (!shadow.tables[i].shadow)
+ continue;
+
+ baser_phys = virt_to_phys(shadow.tables[i].shadow);
+ if (IS_ENABLED(CONFIG_ARM64_64K_PAGES) && (baser_phys >> 48))
+ baser_phys = GITS_BASER_PHYS_52_to_48(baser_phys);
+
+ its->tables[i].val &= ~GENMASK(47, 12);
+ its->tables[i].val |= baser_phys;
+ its->tables[i].base = shadow.tables[i].shadow;
+ }
+
+ return 0;
+}
+
+int its_end_depriviledge(int ret_pkvm_finalize, unsigned long *flags, its_init_emulate cb)
+{
+ struct its_node *its;
+ int i = 0, ret = 0;
+
+ if (!flags || !cb)
+ return -EINVAL;
+
+ list_for_each_entry(its, &its_nodes, entry) {
+ if (!ret_pkvm_finalize && !ret)
+ ret = its_switch_to_shadow_locked(its, cb);
+
+ raw_spin_unlock_irqrestore(&its->lock, flags[i++]);
+ }
+
+ kfree(flags);
+ raw_spin_unlock(&its_lock);
+
+ return ret;
+}
+EXPORT_SYMBOL_GPL(its_end_depriviledge);
+
static int __init its_probe_one(struct its_node *its)
{
u64 baser, tmp;
diff --git a/include/linux/irqchip/arm-gic-v3.h b/include/linux/irqchip/arm-gic-v3.h
index 0225121f3013..40457a4375d4 100644
--- a/include/linux/irqchip/arm-gic-v3.h
+++ b/include/linux/irqchip/arm-gic-v3.h
@@ -657,6 +657,30 @@ static inline bool gic_enable_sre(void)
return !!(val & ICC_SRE_EL1_SRE);
}

+/*
+ * The ITS_BASER structure - contains memory information, cached
+ * value of BASER register configuration and ITS page size.
+ */
+struct its_baser {
+ void *base;
+ void *shadow;
+ u64 val;
+ u32 order;
+ u32 psz;
+};
+
+struct its_shadow_tables {
+ struct its_baser tables[GITS_BASER_NR_REGS];
+ void *cmd_shadow;
+ void *cmd_original;
+ size_t cmdq_len;
+};
+
+typedef int (*its_init_emulate)(phys_addr_t its_phys_base, struct its_shadow_tables *shadow);
+
+void *its_start_depriviledge(void);
+int its_end_depriviledge(int ret, unsigned long *flags, its_init_emulate cb);
+
#endif

#endif
--
2.53.0.473.g4a7958ca14-goog