[PATCH V2] irqchip/gic-v4.1:Check whether indirect table is supported in allocate_vpe_l1_table

[PATCH V2] irqchip/gic-v4.1:Check whether indirect table is supported in allocate_vpe_l1_table

[Nianyao Tang]

In allocate_vpe_l1_table, it allocates a new vpe table without checking
whether indirect table is supported.
ARM allows vendors to support only flat tables. Let's first check if
indirect tables are supported before using it.

Signed-off-by: Nianyao Tang <tangnianyao@huawei.com>
---
 drivers/irqchip/irq-gic-v3-its.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/irqchip/irq-gic-v3-its.c b/drivers/irqchip/irq-gic-v3-its.c
index 467cb78435a9..a4d719720e61 100644
--- a/drivers/irqchip/irq-gic-v3-its.c
+++ b/drivers/irqchip/irq-gic-v3-its.c
@@ -2903,6 +2903,7 @@ static int allocate_vpe_l1_table(void)
 	unsigned int psz = SZ_64K;
 	unsigned int np, epp, esz;
 	struct page *page;
+	bool indirect;
 
 	if (!gic_rdists->has_rvpeid)
 		return 0;
@@ -2937,10 +2938,12 @@ static int allocate_vpe_l1_table(void)
 
 	/* First probe the page size */
 	val = FIELD_PREP(GICR_VPROPBASER_4_1_PAGE_SIZE, GIC_PAGE_SIZE_64K);
+	val |= GICR_VPROPBASER_4_1_INDIRECT;
 	gicr_write_vpropbaser(val, vlpi_base + GICR_VPROPBASER);
 	val = gicr_read_vpropbaser(vlpi_base + GICR_VPROPBASER);
 	gpsz = FIELD_GET(GICR_VPROPBASER_4_1_PAGE_SIZE, val);
 	esz = FIELD_GET(GICR_VPROPBASER_4_1_ENTRY_SIZE, val);
+	indirect = !!(val & GICR_VPROPBASER_4_1_INDIRECT);
 
 	switch (gpsz) {
 	default:
@@ -2973,7 +2976,7 @@ static int allocate_vpe_l1_table(void)
 	 * If we need more than just a single L1 page, flag the table
 	 * as indirect and compute the number of required L1 pages.
 	 */
-	if (epp < ITS_MAX_VPEID) {
+	if (epp < ITS_MAX_VPEID && indirect) {
 		int nl2;
 
 		val |= GICR_VPROPBASER_4_1_INDIRECT;
@@ -2984,7 +2987,8 @@ static int allocate_vpe_l1_table(void)
 		/* Number of L1 pages to point to the L2 pages */
 		npg = DIV_ROUND_UP(nl2 * SZ_8, psz);
 	} else {
-		npg = 1;
+		npg = DIV_ROUND_UP(ITS_MAX_VPEID, epp);
+		npg = clamp_val(npg, 1, (GICR_VPROPBASER_4_1_SIZE + 1));
 	}
 
 	val |= FIELD_PREP(GICR_VPROPBASER_4_1_SIZE, npg - 1);
-- 
2.33.0

Re: [PATCH V2] irqchip/gic-v4.1:Check whether indirect table is supported in allocate_vpe_l1_table

[Marc Zyngier]

On Thu, 18 Sep 2025 15:15:57 +0100,
Nianyao Tang <tangnianyao@huawei.com> wrote:
> 
> In allocate_vpe_l1_table, it allocates a new vpe table without checking
> whether indirect table is supported.
> ARM allows vendors to support only flat tables. Let's first check if
> indirect tables are supported before using it.
> 
> Signed-off-by: Nianyao Tang <tangnianyao@huawei.com>

As I understand it, this is for the same machines that also requires
[1] and [2] to be able to use vLPIs and vSGIs.

I seriously doubt that we want *any* of it (creating userspace ABI to
deal with a broken design is not something I'm keen on).

Frankly, you should consider disabling GICv4.1 on these machines, and
stick with GICv3 (which I assume works correctly).

Thanks,

	M.

[1] https://lore.kernel.org/r/20250825023954.3516381-1-wangzhou1@hisilicon.com
[2] https://lore.kernel.org/r/20250909110615.129179-1-wangzhou1@hisilicon.com

-- 
Without deviation from the norm, progress is not possible.